Bug 1936278 - Prevent search mode chiclet from being dismissed when clicking in page...

[gecko.git] / dom / bindings / Codegen.py

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at http://mozilla.org/MPL/2.0/.

# Common codegen classes.

import functools
import math
from operator import attrgetter
import os
import re
import string
import textwrap

from Configuration import (
    Descriptor,
    MemberIsLegacyUnforgeable,
    NoSuchDescriptorError,
    getAllTypes,
    getTypesFromCallback,
    getTypesFromDescriptor,
    getTypesFromDictionary,
)
from perfecthash import PerfectHash
from WebIDL import (
    BuiltinTypes,
    IDLAttribute,
    IDLBuiltinType,
    IDLDefaultDictionaryValue,
    IDLDictionary,
    IDLEmptySequenceValue,
    IDLInterfaceMember,
    IDLNullValue,
    IDLSequenceType,
    IDLType,
    IDLUndefinedValue,
)

AUTOGENERATED_WARNING_COMMENT = (
    "/* THIS FILE IS AUTOGENERATED BY Codegen.py - DO NOT EDIT */\n\n"
)
AUTOGENERATED_WITH_SOURCE_WARNING_COMMENT = (
    "/* THIS FILE IS AUTOGENERATED FROM %s BY Codegen.py - DO NOT EDIT */\n\n"
)
ADDPROPERTY_HOOK_NAME = "_addProperty"
GETWRAPPERCACHE_HOOK_NAME = "_getWrapperCache"
FINALIZE_HOOK_NAME = "_finalize"
OBJECT_MOVED_HOOK_NAME = "_objectMoved"
CONSTRUCT_HOOK_NAME = "_constructor"
LEGACYCALLER_HOOK_NAME = "_legacycaller"
RESOLVE_HOOK_NAME = "_resolve"
MAY_RESOLVE_HOOK_NAME = "_mayResolve"
NEW_ENUMERATE_HOOK_NAME = "_newEnumerate"
INSTANCE_RESERVED_SLOTS = 1

# This size is arbitrary. It is a power of 2 to make using it as a modulo
# operand cheap, and is usually around 1/3-1/5th of the set size (sometimes
# smaller for very large sets).
GLOBAL_NAMES_PHF_SIZE = 256


def reservedSlot(slotIndex, forXray):
    base = "DOM_EXPANDO_RESERVED_SLOTS" if forXray else "DOM_INSTANCE_RESERVED_SLOTS"
    return "(%s + %d)" % (base, slotIndex)


def getSlotIndex(member, descriptor):
    slotIndex = member.slotIndices[descriptor.interface.identifier.name]
    return slotIndex[0] if isinstance(slotIndex, tuple) else slotIndex


def memberReservedSlot(member, descriptor):
    return reservedSlot(getSlotIndex(member, descriptor), False)


def memberXrayExpandoReservedSlot(member, descriptor):
    return reservedSlot(getSlotIndex(member, descriptor), True)


def mayUseXrayExpandoSlots(descriptor, attr):
    assert not attr.getExtendedAttribute("NewObject")
    # For attributes whose type is a Gecko interface we always use
    # slots on the reflector for caching.  Also, for interfaces that
    # don't want Xrays we obviously never use the Xray expando slot.
    return descriptor.wantsXrays and not attr.type.isGeckoInterface()


def reflectedHTMLAttributesArrayIndex(descriptor, attr):
    slots = attr.slotIndices[descriptor.interface.identifier.name]
    return slots[1]


def getReflectedHTMLAttributesIface(descriptor):
    iface = descriptor.interface
    while iface:
        if iface.reflectedHTMLAttributesReturningFrozenArray:
            return iface
        iface = iface.parent
    return None


def toStringBool(arg):
    """
    Converts IDL/Python Boolean (True/False) to C++ Boolean (true/false)
    """
    return str(not not arg).lower()


def toBindingNamespace(arg):
    return arg + "_Binding"


def isTypeCopyConstructible(type):
    # Nullable and sequence stuff doesn't affect copy-constructibility
    type = type.unroll()
    return (
        type.isUndefined()
        or type.isPrimitive()
        or type.isString()
        or type.isEnum()
        or (type.isUnion() and CGUnionStruct.isUnionCopyConstructible(type))
        or (
            type.isDictionary()
            and CGDictionary.isDictionaryCopyConstructible(type.inner)
        )
        or
        # Interface types are only copy-constructible if they're Gecko
        # interfaces.  SpiderMonkey interfaces are not copy-constructible
        # because of rooting issues.
        (type.isInterface() and type.isGeckoInterface())
    )


class CycleCollectionUnsupported(TypeError):
    def __init__(self, message):
        TypeError.__init__(self, message)


def idlTypeNeedsCycleCollection(type):
    type = type.unroll()  # Takes care of sequences and nullables
    if (
        (type.isPrimitive() and type.tag() in builtinNames)
        or type.isUndefined()
        or type.isEnum()
        or type.isString()
        or type.isAny()
        or type.isObject()
        or type.isSpiderMonkeyInterface()
    ):
        return False
    elif type.isCallback() or type.isPromise() or type.isGeckoInterface():
        return True
    elif type.isUnion():
        return any(idlTypeNeedsCycleCollection(t) for t in type.flatMemberTypes)
    elif type.isRecord():
        if idlTypeNeedsCycleCollection(type.inner):
            raise CycleCollectionUnsupported(
                "Cycle collection for type %s is not supported" % type
            )
        return False
    elif type.isDictionary():
        return CGDictionary.dictionaryNeedsCycleCollection(type.inner)
    else:
        raise CycleCollectionUnsupported(
            "Don't know whether to cycle-collect type %s" % type
        )


def idlTypeNeedsCallContext(type, descriptor=None, allowTreatNonCallableAsNull=False):
    """
    Returns whether the given type needs error reporting via a
    BindingCallContext for JS-to-C++ conversions.  This will happen when the
    conversion can throw an exception due to logic in the IDL spec or
    Gecko-specific security checks.  In particular, a type needs a
    BindingCallContext if and only if the JS-to-C++ conversion for that type can
    end up calling ThrowErrorMessage.

    For some types this depends on the descriptor (e.g. because we do certain
    checks only for some kinds of interfaces).

    The allowTreatNonCallableAsNull optimization is there so we can avoid
    generating an unnecessary BindingCallContext for all the event handler
    attribute setters.

    """
    while True:
        if type.isSequence():
            # Sequences can always throw "not an object"
            return True
        if type.nullable():
            # treatNonObjectAsNull() and treatNonCallableAsNull() are
            # only sane things to test on nullable types, so do that now.
            if (
                allowTreatNonCallableAsNull
                and type.isCallback()
                and (type.treatNonObjectAsNull() or type.treatNonCallableAsNull())
            ):
                # This can't throw. so never needs a method description.
                return False
            type = type.inner
        else:
            break

    if type.isUndefined():
        # Clearly doesn't need a method description; we can only get here from
        # CGHeaders trying to decide whether to include the method description
        # header.
        return False
    # The float check needs to come before the isPrimitive() check,
    # because floats are primitives too.
    if type.isFloat():
        # Floats can throw if restricted.
        return not type.isUnrestricted()
    if type.isPrimitive() and type.tag() in builtinNames:
        # Numbers can throw if enforcing range.
        return type.hasEnforceRange()
    if type.isEnum():
        # Can throw on invalid value.
        return True
    if type.isString():
        # Can throw if it's a ByteString
        return type.isByteString()
    if type.isAny():
        # JS-implemented interfaces do extra security checks so need a
        # method description here.  If we have no descriptor, this
        # might be JS-implemented thing, so it will do the security
        # check and we need the method description.
        return not descriptor or descriptor.interface.isJSImplemented()
    if type.isPromise():
        # JS-to-Promise conversion won't cause us to throw any
        # specific exceptions, so does not need a method description.
        return False
    if (
        type.isObject()
        or type.isInterface()
        or type.isCallback()
        or type.isDictionary()
        or type.isRecord()
        or type.isObservableArray()
    ):
        # These can all throw if a primitive is passed in, at the very least.
        # There are some rare cases when we know we have an object, but those
        # are not worth the complexity of optimizing for.
        #
        # Note that we checked the [LegacyTreatNonObjectAsNull] case already when
        # unwrapping nullables.
        return True
    if type.isUnion():
        # Can throw if a type not in the union is passed in.
        return True
    raise TypeError("Don't know whether type '%s' needs a method description" % type)


# TryPreserveWrapper uses the addProperty hook to preserve the wrapper of
# non-nsISupports cycle collected objects, so if wantsAddProperty is changed
# to not cover that case then TryPreserveWrapper will need to be changed.
def wantsAddProperty(desc):
    return desc.concrete and desc.wrapperCache and not desc.isGlobal()


def wantsGetWrapperCache(desc):
    return (
        desc.concrete and desc.wrapperCache and not desc.isGlobal() and not desc.proxy
    )


def indent(s, indentLevel=2):
    """
    Indent C++ code.

    Weird secret feature: this doesn't indent lines that start with # (such as
    #include lines or #ifdef/#endif).
    """

    # We'll want to insert the indent at the beginnings of lines, but we
    # don't want to indent empty lines.
    padding = indentLevel * " "
    return "\n".join(
        [
            (padding + line) if line and line[0] != "#" else line
            for line in s.split("\n")
        ]
    )


# dedent() and fill() are often called on the same string multiple
# times.  We want to memoize their return values so we don't keep
# recomputing them all the time.
def memoize(fn):
    """
    Decorator to memoize a function of one argument.  The cache just
    grows without bound.
    """
    cache = {}

    @functools.wraps(fn)
    def wrapper(arg):
        retval = cache.get(arg)
        if retval is None:
            retval = cache[arg] = fn(arg)
        return retval

    return wrapper


@memoize
def dedent(s):
    """
    Remove all leading whitespace from s, and remove a blank line
    at the beginning.
    """
    if s.startswith("\n"):
        s = s[1:]
    return textwrap.dedent(s)


# This works by transforming the fill()-template to an equivalent
# string.Template.
fill_multiline_substitution_re = re.compile(r"( *)\$\*{(\w+)}(\n)?")


find_substitutions = re.compile(r"\${")


@memoize
def compile_fill_template(template):
    """
    Helper function for fill().  Given the template string passed to fill(),
    do the reusable part of template processing and return a pair (t,
    argModList) that can be used every time fill() is called with that
    template argument.

    argsModList is list of tuples that represent modifications to be
    made to args.  Each modification has, in order: i) the arg name,
    ii) the modified name, iii) the indent depth.
    """
    t = dedent(template)
    assert t.endswith("\n") or "\n" not in t
    argModList = []

    def replace(match):
        """
        Replaces a line like '  $*{xyz}\n' with '${xyz_n}',
        where n is the indent depth, and add a corresponding entry to
        argModList.

        Note that this needs to close over argModList, so it has to be
        defined inside compile_fill_template().
        """
        indentation, name, nl = match.groups()
        depth = len(indentation)

        # Check that $*{xyz} appears by itself on a line.
        prev = match.string[: match.start()]
        if (prev and not prev.endswith("\n")) or nl is None:
            raise ValueError(
                "Invalid fill() template: $*{%s} must appear by itself on a line" % name
            )

        # Now replace this whole line of template with the indented equivalent.
        modified_name = name + "_" + str(depth)
        argModList.append((name, modified_name, depth))
        return "${" + modified_name + "}"

    t = re.sub(fill_multiline_substitution_re, replace, t)
    if not re.search(find_substitutions, t):
        raise TypeError("Using fill() when dedent() would do.")
    return (string.Template(t), argModList)


def fill(template, **args):
    """
    Convenience function for filling in a multiline template.

    `fill(template, name1=v1, name2=v2)` is a lot like
    `string.Template(template).substitute({"name1": v1, "name2": v2})`.

    However, it's shorter, and has a few nice features:

      * If `template` is indented, fill() automatically dedents it!
        This makes code using fill() with Python's multiline strings
        much nicer to look at.

      * If `template` starts with a blank line, fill() strips it off.
        (Again, convenient with multiline strings.)

      * fill() recognizes a special kind of substitution
        of the form `$*{name}`.

        Use this to paste in, and automatically indent, multiple lines.
        (Mnemonic: The `*` is for "multiple lines").

        A `$*` substitution must appear by itself on a line, with optional
        preceding indentation (spaces only). The whole line is replaced by the
        corresponding keyword argument, indented appropriately.  If the
        argument is an empty string, no output is generated, not even a blank
        line.
    """

    t, argModList = compile_fill_template(template)
    # Now apply argModList to args
    for name, modified_name, depth in argModList:
        if not (args[name] == "" or args[name].endswith("\n")):
            raise ValueError(
                "Argument %s with value %r is missing a newline" % (name, args[name])
            )
        args[modified_name] = indent(args[name], depth)

    return t.substitute(args)


class CGThing:
    """
    Abstract base class for things that spit out code.
    """

    def __init__(self):
        pass  # Nothing for now

    def declare(self):
        """Produce code for a header file."""
        assert False  # Override me!

    def define(self):
        """Produce code for a cpp file."""
        assert False  # Override me!

    def deps(self):
        """Produce the deps for a pp file"""
        assert False  # Override me!


class CGStringTable(CGThing):
    """
    Generate a function accessor for a WebIDL string table, using the existing
    concatenated names string and mapping indexes to offsets in that string:

    const char *accessorName(unsigned int index) {
      static const uint16_t offsets = { ... };
      return BindingName(offsets[index]);
    }

    This is more efficient than the more natural:

    const char *table[] = {
      ...
    };

    The uint16_t offsets are smaller than the pointer equivalents, and the
    concatenated string requires no runtime relocations.
    """

    def __init__(self, accessorName, strings, static=False):
        CGThing.__init__(self)
        self.accessorName = accessorName
        self.strings = strings
        self.static = static

    def declare(self):
        if self.static:
            return ""
        return "const char *%s(unsigned int aIndex);\n" % self.accessorName

    def define(self):
        offsets = []
        for s in self.strings:
            offsets.append(BindingNamesOffsetEnum(s))
        return fill(
            """
            ${static}const char *${name}(unsigned int aIndex)
            {
              static const BindingNamesOffset offsets[] = {
                $*{offsets}
              };
              return BindingName(offsets[aIndex]);
            }
            """,
            static="static " if self.static else "",
            name=self.accessorName,
            offsets="".join("BindingNamesOffset::%s,\n" % o for o in offsets),
        )


class CGNativePropertyHooks(CGThing):
    """
    Generate a NativePropertyHooks for a given descriptor
    """

    def __init__(self, descriptor, properties):
        CGThing.__init__(self)
        assert descriptor.wantsXrays
        self.descriptor = descriptor
        self.properties = properties

    def declare(self):
        return ""

    def define(self):
        if (
            self.descriptor.concrete
            and self.descriptor.proxy
            and not self.descriptor.isMaybeCrossOriginObject()
        ):
            if self.descriptor.needsXrayNamedDeleterHook():
                deleteNamedProperty = "DeleteNamedProperty"
            else:
                deleteNamedProperty = "nullptr"
            namedOrIndexed = fill(
                """
                const NativeNamedOrIndexedPropertyHooks sNativeNamedOrIndexedPropertyHooks = {
                  binding_detail::ResolveOwnProperty,
                  binding_detail::EnumerateOwnProperties,
                  ${deleteNamedProperty}
                };
                """,
                deleteNamedProperty=deleteNamedProperty,
            )
            namedOrIndexedPointer = "&sNativeNamedOrIndexedPropertyHooks"
        elif self.descriptor.needsXrayResolveHooks():
            namedOrIndexed = dedent(
                """
                const NativeNamedOrIndexedPropertyHooks sNativeNamedOrIndexedPropertyHooks = {
                  ResolveOwnPropertyViaResolve,
                  EnumerateOwnPropertiesViaGetOwnPropertyNames,
                  nullptr
                };
                """
            )
            namedOrIndexedPointer = "&sNativeNamedOrIndexedPropertyHooks"
        else:
            namedOrIndexed = ""
            namedOrIndexedPointer = "nullptr"
        if self.properties.hasNonChromeOnly():
            regular = "sNativeProperties.Upcast()"
        else:
            regular = "nullptr"
        if self.properties.hasChromeOnly():
            chrome = "sChromeOnlyNativeProperties.Upcast()"
        else:
            chrome = "nullptr"
        constructorID = "constructors::id::"
        if self.descriptor.interface.hasInterfaceObject():
            constructorID += self.descriptor.name
        else:
            constructorID += "_ID_Count"
        prototypeID = "prototypes::id::"
        if self.descriptor.interface.hasInterfacePrototypeObject():
            prototypeID += self.descriptor.name
        else:
            prototypeID += "_ID_Count"

        if self.descriptor.wantsXrayExpandoClass:
            expandoClass = "&sXrayExpandoObjectClass"
        else:
            expandoClass = "&DefaultXrayExpandoObjectClass"

        return namedOrIndexed + fill(
            """
            bool sNativePropertiesInited = false;
            const NativePropertyHooks sNativePropertyHooks = {
              ${namedOrIndexedPointer},
              { ${regular}, ${chrome}, &sNativePropertiesInited },
              ${prototypeID},
              ${constructorID},
              ${expandoClass}
            };
            """,
            namedOrIndexedPointer=namedOrIndexedPointer,
            regular=regular,
            chrome=chrome,
            prototypeID=prototypeID,
            constructorID=constructorID,
            expandoClass=expandoClass,
        )


def NativePropertyHooks(descriptor):
    return (
        "&sEmptyNativePropertyHooks"
        if not descriptor.wantsXrays
        else "&sNativePropertyHooks"
    )


def DOMClass(descriptor):
    protoList = ["prototypes::id::" + proto for proto in descriptor.prototypeNameChain]
    # Pad out the list to the right length with _ID_Count so we
    # guarantee that all the lists are the same length.  _ID_Count
    # is never the ID of any prototype, so it's safe to use as
    # padding.
    protoList.extend(
        ["prototypes::id::_ID_Count"]
        * (descriptor.config.maxProtoChainLength - len(protoList))
    )

    if descriptor.interface.isSerializable():
        serializer = "Serialize"
    else:
        serializer = "nullptr"

    if wantsGetWrapperCache(descriptor):
        wrapperCacheGetter = GETWRAPPERCACHE_HOOK_NAME
    else:
        wrapperCacheGetter = "nullptr"

    if descriptor.hasOrdinaryObjectPrototype():
        getProto = "JS::GetRealmObjectPrototypeHandle"
    else:
        getProto = "GetProtoObjectHandle"

    return fill(
        """
          { ${protoChain} },
          std::is_base_of_v<nsISupports, ${nativeType}>,
          ${hooks},
          FindAssociatedGlobalForNative<${nativeType}>::Get,
          ${getProto},
          GetCCParticipant<${nativeType}>::Get(),
          ${serializer},
          ${wrapperCacheGetter}
        """,
        protoChain=", ".join(protoList),
        nativeType=descriptor.nativeType,
        hooks=NativePropertyHooks(descriptor),
        serializer=serializer,
        wrapperCacheGetter=wrapperCacheGetter,
        getProto=getProto,
    )


def InstanceReservedSlots(descriptor):
    slots = INSTANCE_RESERVED_SLOTS + descriptor.interface.totalMembersInSlots
    if descriptor.isMaybeCrossOriginObject():
        # We need a slot for the cross-origin holder too.
        if descriptor.interface.hasChildInterfaces():
            raise TypeError(
                "We don't support non-leaf cross-origin interfaces "
                "like %s" % descriptor.interface.identifier.name
            )
        slots += 1
    return slots


class CGDOMJSClass(CGThing):
    """
    Generate a DOMJSClass for a given descriptor
    """

    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        return ""

    def define(self):
        callHook = (
            LEGACYCALLER_HOOK_NAME
            if self.descriptor.operations["LegacyCaller"]
            else "nullptr"
        )
        objectMovedHook = (
            OBJECT_MOVED_HOOK_NAME if self.descriptor.wrapperCache else "nullptr"
        )
        slotCount = InstanceReservedSlots(self.descriptor)
        classFlags = "JSCLASS_IS_DOMJSCLASS | JSCLASS_FOREGROUND_FINALIZE | "
        if self.descriptor.isGlobal():
            classFlags += (
                "JSCLASS_DOM_GLOBAL | JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(DOM_GLOBAL_SLOTS)"
            )
            traceHook = "JS_GlobalObjectTraceHook"
            reservedSlots = "JSCLASS_GLOBAL_APPLICATION_SLOTS"
        else:
            classFlags += "JSCLASS_HAS_RESERVED_SLOTS(%d)" % slotCount
            iface = getReflectedHTMLAttributesIface(self.descriptor)
            if iface:
                traceHook = (
                    "%s::ReflectedHTMLAttributeSlots::Trace"
                    % toBindingNamespace(iface.identifier.name)
                )
            else:
                traceHook = "nullptr"
            reservedSlots = slotCount
        if self.descriptor.interface.hasProbablyShortLivingWrapper():
            if not self.descriptor.wrapperCache:
                raise TypeError(
                    "Need a wrapper cache to support nursery "
                    "allocation of DOM objects"
                )
            classFlags += " | JSCLASS_SKIP_NURSERY_FINALIZE"

        if self.descriptor.interface.getExtendedAttribute("NeedResolve"):
            resolveHook = RESOLVE_HOOK_NAME
            mayResolveHook = MAY_RESOLVE_HOOK_NAME
            newEnumerateHook = NEW_ENUMERATE_HOOK_NAME
        elif self.descriptor.isGlobal():
            resolveHook = "mozilla::dom::ResolveGlobal"
            mayResolveHook = "mozilla::dom::MayResolveGlobal"
            newEnumerateHook = "mozilla::dom::EnumerateGlobal"
        else:
            resolveHook = "nullptr"
            mayResolveHook = "nullptr"
            newEnumerateHook = "nullptr"

        return fill(
            """
            static const JSClassOps sClassOps = {
              ${addProperty}, /* addProperty */
              nullptr,               /* delProperty */
              nullptr,               /* enumerate */
              ${newEnumerate}, /* newEnumerate */
              ${resolve}, /* resolve */
              ${mayResolve}, /* mayResolve */
              ${finalize}, /* finalize */
              ${call}, /* call */
              nullptr,               /* construct */
              ${trace}, /* trace */
            };

            static const js::ClassExtension sClassExtension = {
              ${objectMoved} /* objectMovedOp */
            };

            static const DOMJSClass sClass = {
              { "${name}",
                ${flags},
                &sClassOps,
                JS_NULL_CLASS_SPEC,
                &sClassExtension,
                JS_NULL_OBJECT_OPS
              },
              $*{descriptor}
            };
            static_assert(${instanceReservedSlots} == DOM_INSTANCE_RESERVED_SLOTS,
                          "Must have the right minimal number of reserved slots.");
            static_assert(${reservedSlots} >= ${slotCount},
                          "Must have enough reserved slots.");
            """,
            name=self.descriptor.interface.getClassName(),
            flags=classFlags,
            addProperty=(
                ADDPROPERTY_HOOK_NAME
                if wantsAddProperty(self.descriptor)
                else "nullptr"
            ),
            newEnumerate=newEnumerateHook,
            resolve=resolveHook,
            mayResolve=mayResolveHook,
            finalize=FINALIZE_HOOK_NAME,
            call=callHook,
            trace=traceHook,
            objectMoved=objectMovedHook,
            descriptor=DOMClass(self.descriptor),
            instanceReservedSlots=INSTANCE_RESERVED_SLOTS,
            reservedSlots=reservedSlots,
            slotCount=slotCount,
        )


class CGDOMProxyJSClass(CGThing):
    """
    Generate a DOMJSClass for a given proxy descriptor
    """

    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        return ""

    def define(self):
        slotCount = InstanceReservedSlots(self.descriptor)
        # We need one reserved slot (DOM_OBJECT_SLOT).
        flags = ["JSCLASS_IS_DOMJSCLASS", "JSCLASS_HAS_RESERVED_SLOTS(%d)" % slotCount]
        # We don't use an IDL annotation for JSCLASS_EMULATES_UNDEFINED because
        # we don't want people ever adding that to any interface other than
        # HTMLAllCollection.  So just hardcode it here.
        if self.descriptor.interface.identifier.name == "HTMLAllCollection":
            flags.append("JSCLASS_EMULATES_UNDEFINED")
        return fill(
            """
            static const DOMJSClass sClass = {
              PROXY_CLASS_DEF("${name}",
                              ${flags}),
              $*{descriptor}
            };
            """,
            name=self.descriptor.interface.identifier.name,
            flags=" | ".join(flags),
            descriptor=DOMClass(self.descriptor),
        )


class CGXrayExpandoJSClass(CGThing):
    """
    Generate a JSClass for an Xray expando object.  This is only
    needed if we have members in slots (for [Cached] or [StoreInSlot]
    stuff).
    """

    def __init__(self, descriptor):
        assert descriptor.interface.totalMembersInSlots != 0
        assert descriptor.wantsXrays
        assert descriptor.wantsXrayExpandoClass
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        return ""

    def define(self):
        iface = getReflectedHTMLAttributesIface(self.descriptor)
        if iface:
            ops = (
                "&%s::ReflectedHTMLAttributeSlots::sXrayExpandoObjectClassOps"
                % toBindingNamespace(iface.identifier.name)
            )
        else:
            ops = "&xpc::XrayExpandoObjectClassOps"
        return fill(
            """
            // This may allocate too many slots, because we only really need
            // slots for our non-interface-typed members that we cache.  But
            // allocating slots only for those would make the slot index
            // computations much more complicated, so let's do this the simple
            // way for now.
            DEFINE_XRAY_EXPANDO_CLASS_WITH_OPS(static, sXrayExpandoObjectClass, ${memberSlots},
                                               ${ops});
            """,
            memberSlots=self.descriptor.interface.totalMembersInSlots,
            ops=ops,
        )


def PrototypeIDAndDepth(descriptor):
    prototypeID = "prototypes::id::"
    if descriptor.interface.hasInterfacePrototypeObject():
        prototypeID += descriptor.interface.identifier.name
        depth = "PrototypeTraits<%s>::Depth" % prototypeID
    else:
        prototypeID += "_ID_Count"
        depth = "0"
    return (prototypeID, depth)


def InterfacePrototypeObjectProtoGetter(descriptor):
    """
    Returns a tuple with two elements:

        1) The name of the function to call to get the prototype to use for the
           interface prototype object as a JSObject*.

        2) The name of the function to call to get the prototype to use for the
           interface prototype object as a JS::Handle<JSObject*> or None if no
           such function exists.
    """
    parentProtoName = descriptor.parentPrototypeName
    if descriptor.hasNamedPropertiesObject:
        protoGetter = "GetNamedPropertiesObject"
        protoHandleGetter = None
    elif parentProtoName is None:
        protoHandleGetter = None
        if descriptor.interface.getExtendedAttribute("ExceptionClass"):
            protoGetter = "JS::GetRealmErrorPrototype"
        elif descriptor.interface.isIteratorInterface():
            protoGetter = "JS::GetRealmIteratorPrototype"
        elif descriptor.interface.isAsyncIteratorInterface():
            protoGetter = "JS::GetRealmAsyncIteratorPrototype"
        else:
            protoGetter = "JS::GetRealmObjectPrototype"
            protoHandleGetter = "JS::GetRealmObjectPrototypeHandle"
    else:
        prefix = toBindingNamespace(parentProtoName)
        protoGetter = prefix + "::GetProtoObject"
        protoHandleGetter = prefix + "::GetProtoObjectHandle"

    return (protoGetter, protoHandleGetter)


class CGPrototypeJSClass(CGThing):
    def __init__(self, descriptor, properties):
        CGThing.__init__(self)
        self.descriptor = descriptor
        self.properties = properties

    def declare(self):
        # We're purely for internal consumption
        return ""

    def define(self):
        prototypeID, depth = PrototypeIDAndDepth(self.descriptor)
        slotCount = "DOM_INTERFACE_PROTO_SLOTS_BASE"
        # Globals handle unforgeables directly in Wrap() instead of
        # via a holder.
        if (
            self.descriptor.hasLegacyUnforgeableMembers
            and not self.descriptor.isGlobal()
        ):
            slotCount += (
                " + 1 /* slot for the JSObject holding the unforgeable properties */"
            )
        (protoGetter, _) = InterfacePrototypeObjectProtoGetter(self.descriptor)
        type = (
            "eGlobalInterfacePrototype"
            if self.descriptor.isGlobal()
            else "eInterfacePrototype"
        )
        return fill(
            """
            static const DOMIfaceAndProtoJSClass sPrototypeClass = {
              {
                "${name}Prototype",
                JSCLASS_IS_DOMIFACEANDPROTOJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(${slotCount}),
                JS_NULL_CLASS_OPS,
                JS_NULL_CLASS_SPEC,
                JS_NULL_CLASS_EXT,
                JS_NULL_OBJECT_OPS
              },
              ${type},
              ${prototypeID},
              ${depth},
              ${hooks},
              ${protoGetter}
            };
            """,
            name=self.descriptor.interface.getClassName(),
            slotCount=slotCount,
            type=type,
            hooks=NativePropertyHooks(self.descriptor),
            prototypeID=prototypeID,
            depth=depth,
            protoGetter=protoGetter,
        )


def InterfaceObjectProtoGetter(descriptor):
    """
    Returns the name of the function to call to get the prototype to use for the
    interface object's prototype as a JS::Handle<JSObject*>.
    """
    assert not descriptor.interface.isNamespace()
    parentInterface = descriptor.interface.parent
    if parentInterface:
        parentIfaceName = parentInterface.identifier.name
        parentDesc = descriptor.getDescriptor(parentIfaceName)
        prefix = toBindingNamespace(parentDesc.name)
        protoHandleGetter = prefix + "::GetConstructorObjectHandle"
    else:
        protoHandleGetter = "JS::GetRealmFunctionPrototypeHandle"
    return protoHandleGetter


class CGNamespaceObjectJSClass(CGThing):
    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        # We're purely for internal consumption
        return ""

    def define(self):
        classString = self.descriptor.interface.getExtendedAttribute("ClassString")
        if classString is None:
            classString = self.descriptor.interface.identifier.name
        else:
            classString = classString[0]
        return fill(
            """
            static const DOMIfaceAndProtoJSClass sNamespaceObjectClass = {
              {
                "${classString}",
                JSCLASS_IS_DOMIFACEANDPROTOJSCLASS,
                JS_NULL_CLASS_OPS,
                JS_NULL_CLASS_SPEC,
                JS_NULL_CLASS_EXT,
                JS_NULL_OBJECT_OPS
              },
              eNamespace,
              prototypes::id::_ID_Count,
              0,
              ${hooks},
              // This isn't strictly following the spec (see
              // https://console.spec.whatwg.org/#ref-for-dfn-namespace-object),
              // but should be ok for Xrays.
              JS::GetRealmObjectPrototype
            };
            """,
            classString=classString,
            hooks=NativePropertyHooks(self.descriptor),
        )


class CGInterfaceObjectInfo(CGThing):
    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        # We're purely for internal consumption
        return ""

    def define(self):
        if self.descriptor.interface.ctor():
            ctorname = CONSTRUCT_HOOK_NAME
            constructorArgs = methodLength(self.descriptor.interface.ctor())
        else:
            ctorname = "ThrowingConstructor"
            constructorArgs = 0
        constructorName = self.descriptor.interface.getClassName()
        wantsIsInstance = self.descriptor.interface.hasInterfacePrototypeObject()

        prototypeID, depth = PrototypeIDAndDepth(self.descriptor)
        protoHandleGetter = InterfaceObjectProtoGetter(self.descriptor)

        return fill(
            """
            static const DOMInterfaceInfo sInterfaceObjectInfo = {
              { ${ctorname}, ${hooks} },
              ${protoHandleGetter},
              ${depth},
              ${prototypeID},
              ${wantsIsInstance},
              ${constructorArgs},
              "${constructorName}",
            };
            """,
            ctorname=ctorname,
            hooks=NativePropertyHooks(self.descriptor),
            protoHandleGetter=protoHandleGetter,
            depth=depth,
            prototypeID=prototypeID,
            wantsIsInstance=toStringBool(wantsIsInstance),
            constructorArgs=constructorArgs,
            constructorName=constructorName,
        )


class CGList(CGThing):
    """
    Generate code for a list of GCThings.  Just concatenates them together, with
    an optional joiner string.  "\n" is a common joiner.
    """

    def __init__(self, children, joiner=""):
        CGThing.__init__(self)
        # Make a copy of the kids into a list, because if someone passes in a
        # generator we won't be able to both declare and define ourselves, or
        # define ourselves more than once!
        self.children = list(children)
        self.joiner = joiner

    def append(self, child):
        self.children.append(child)

    def prepend(self, child):
        self.children.insert(0, child)

    def extend(self, kids):
        self.children.extend(kids)

    def join(self, iterable):
        return self.joiner.join(s for s in iterable if len(s) > 0)

    def declare(self):
        return self.join(
            child.declare() for child in self.children if child is not None
        )

    def define(self):
        return self.join(child.define() for child in self.children if child is not None)

    def deps(self):
        deps = set()
        for child in self.children:
            if child is None:
                continue
            deps = deps.union(child.deps())
        return deps

    def __len__(self):
        return len(self.children)


class CGGeneric(CGThing):
    """
    A class that spits out a fixed string into the codegen.  Can spit out a
    separate string for the declaration too.
    """

    def __init__(self, define="", declare=""):
        self.declareText = declare
        self.defineText = define

    def declare(self):
        return self.declareText

    def define(self):
        return self.defineText

    def deps(self):
        return set()


class CGIndenter(CGThing):
    """
    A class that takes another CGThing and generates code that indents that
    CGThing by some number of spaces.  The default indent is two spaces.
    """

    def __init__(self, child, indentLevel=2, declareOnly=False):
        assert isinstance(child, CGThing)
        CGThing.__init__(self)
        self.child = child
        self.indentLevel = indentLevel
        self.declareOnly = declareOnly

    def declare(self):
        return indent(self.child.declare(), self.indentLevel)

    def define(self):
        defn = self.child.define()
        if self.declareOnly:
            return defn
        else:
            return indent(defn, self.indentLevel)


class CGWrapper(CGThing):
    """
    Generic CGThing that wraps other CGThings with pre and post text.
    """

    def __init__(
        self,
        child,
        pre="",
        post="",
        declarePre=None,
        declarePost=None,
        definePre=None,
        definePost=None,
        declareOnly=False,
        defineOnly=False,
        reindent=False,
    ):
        CGThing.__init__(self)
        self.child = child
        self.declarePre = declarePre or pre
        self.declarePost = declarePost or post
        self.definePre = definePre or pre
        self.definePost = definePost or post
        self.declareOnly = declareOnly
        self.defineOnly = defineOnly
        self.reindent = reindent

    def declare(self):
        if self.defineOnly:
            return ""
        decl = self.child.declare()
        if self.reindent:
            decl = self.reindentString(decl, self.declarePre)
        return self.declarePre + decl + self.declarePost

    def define(self):
        if self.declareOnly:
            return ""
        defn = self.child.define()
        if self.reindent:
            defn = self.reindentString(defn, self.definePre)
        return self.definePre + defn + self.definePost

    @staticmethod
    def reindentString(stringToIndent, widthString):
        # We don't use lineStartDetector because we don't want to
        # insert whitespace at the beginning of our _first_ line.
        # Use the length of the last line of width string, in case
        # it is a multiline string.
        lastLineWidth = len(widthString.splitlines()[-1])
        return stripTrailingWhitespace(
            stringToIndent.replace("\n", "\n" + (" " * lastLineWidth))
        )

    def deps(self):
        return self.child.deps()


class CGIfWrapper(CGList):
    def __init__(self, child, condition):
        CGList.__init__(
            self,
            [
                CGWrapper(
                    CGGeneric(condition), pre="if (", post=") {\n", reindent=True
                ),
                CGIndenter(child),
                CGGeneric("}\n"),
            ],
        )


class CGIfElseWrapper(CGList):
    def __init__(self, condition, ifTrue, ifFalse):
        CGList.__init__(
            self,
            [
                CGWrapper(
                    CGGeneric(condition), pre="if (", post=") {\n", reindent=True
                ),
                CGIndenter(ifTrue),
                CGGeneric("} else {\n"),
                CGIndenter(ifFalse),
                CGGeneric("}\n"),
            ],
        )


class CGElseChain(CGThing):
    """
    Concatenate if statements in an if-else-if-else chain.
    """

    def __init__(self, children):
        self.children = [c for c in children if c is not None]

    def declare(self):
        assert False

    def define(self):
        if not self.children:
            return ""
        s = self.children[0].define()
        assert s.endswith("\n")
        for child in self.children[1:]:
            code = child.define()
            assert code.startswith("if") or code.startswith("{")
            assert code.endswith("\n")
            s = s.rstrip() + " else " + code
        return s


class CGTemplatedType(CGWrapper):
    def __init__(self, templateName, child, isConst=False, isReference=False):
        if isinstance(child, list):
            child = CGList(child, ", ")
        const = "const " if isConst else ""
        pre = "%s%s<" % (const, templateName)
        ref = "&" if isReference else ""
        post = ">%s" % ref
        CGWrapper.__init__(self, child, pre=pre, post=post)


class CGNamespace(CGThing):
    """
    Generates namespace block that wraps other CGThings.
    """

    def __init__(self, namespace, child):
        CGThing.__init__(self)
        self.child = child
        self.pre = "namespace %s {\n" % namespace
        self.post = "} // namespace %s\n" % namespace

    def declare(self):
        decl = self.child.declare()
        if len(decl.strip()) == 0:
            return ""
        return self.pre + decl + self.post

    def define(self):
        defn = self.child.define()
        if len(defn.strip()) == 0:
            return ""
        return self.pre + defn + self.post

    def deps(self):
        return self.child.deps()

    @staticmethod
    def build(namespaces, child):
        """
        Static helper method to build multiple wrapped namespaces.
        """
        if not namespaces:
            return CGWrapper(child)
        return CGNamespace("::".join(namespaces), child)


class CGIncludeGuard(CGWrapper):
    """
    Generates include guards for a header.
    """

    def __init__(self, prefix, child):
        """|prefix| is the filename without the extension."""
        define = "DOM_%s_H_" % prefix.upper()
        CGWrapper.__init__(
            self,
            child,
            declarePre="#ifndef %s\n#define %s\n\n" % (define, define),
            declarePost="\n#endif // %s\n" % define,
        )


class CGHeaders(CGWrapper):
    """
    Generates the appropriate include statements.
    """

    def __init__(
        self,
        descriptors,
        dictionaries,
        callbacks,
        callbackDescriptors,
        declareIncludes,
        defineIncludes,
        prefix,
        child,
        config=None,
        jsImplementedDescriptors=[],
    ):
        """
        Builds a set of includes to cover |descriptors|.

        Also includes the files in |declareIncludes| in the header
        file and the files in |defineIncludes| in the .cpp.

        |prefix| contains the basename of the file that we generate include
        statements for.
        """

        # Determine the filenames for which we need headers.
        interfaceDeps = [d.interface for d in descriptors]
        ancestors = []
        for iface in interfaceDeps:
            if iface.parent:
                # We're going to need our parent's prototype, to use as the
                # prototype of our prototype object.
                ancestors.append(iface.parent)
                # And if we have an interface object, we'll need the nearest
                # ancestor with an interface object too, so we can use its
                # interface object as the proto of our interface object.
                if iface.hasInterfaceObject():
                    parent = iface.parent
                    while parent and not parent.hasInterfaceObject():
                        parent = parent.parent
                    if parent:
                        ancestors.append(parent)
        interfaceDeps.extend(ancestors)

        # Include parent interface headers needed for default toJSON code.
        jsonInterfaceParents = []
        for desc in descriptors:
            if not desc.hasDefaultToJSON:
                continue
            parent = desc.interface.parent
            while parent:
                parentDesc = desc.getDescriptor(parent.identifier.name)
                if parentDesc.hasDefaultToJSON:
                    jsonInterfaceParents.append(parentDesc.interface)
                parent = parent.parent
        interfaceDeps.extend(jsonInterfaceParents)

        bindingIncludes = set(self.getDeclarationFilename(d) for d in interfaceDeps)

        # Grab all the implementation declaration files we need.
        implementationIncludes = set(
            d.headerFile for d in descriptors if d.needsHeaderInclude()
        )

        # Now find all the things we'll need as arguments because we
        # need to wrap or unwrap them.
        bindingHeaders = set()
        declareIncludes = set(declareIncludes)

        def addHeadersForType(typeAndPossibleOriginType):
            """
            Add the relevant headers for this type.  We use its origin type, if
            passed, to decide what to do with interface types.
            """
            t, originType = typeAndPossibleOriginType
            isFromDictionary = originType and originType.isDictionary()
            isFromCallback = originType and originType.isCallback()
            # Dictionaries have members that need to be actually
            # declared, not just forward-declared.
            # Callbacks have nullable union arguments that need to be actually
            # declared, not just forward-declared.
            if isFromDictionary:
                headerSet = declareIncludes
            elif isFromCallback and t.nullable() and t.isUnion():
                headerSet = declareIncludes
            else:
                headerSet = bindingHeaders
            # Strip off outer layers and add headers they might require.  (This
            # is conservative: only nullable non-pointer types need Nullable.h;
            # only sequences or observable arrays outside unions need
            # ForOfIterator.h; only functions that return, and attributes that
            # are, sequences or observable arrays in interfaces need Array.h, &c.)
            unrolled = t
            while True:
                if idlTypeNeedsCallContext(unrolled):
                    bindingHeaders.add("mozilla/dom/BindingCallContext.h")
                if unrolled.nullable():
                    headerSet.add("mozilla/dom/Nullable.h")
                elif unrolled.isSequence() or unrolled.isObservableArray():
                    bindingHeaders.add("js/Array.h")
                    bindingHeaders.add("js/ForOfIterator.h")
                    if unrolled.isObservableArray():
                        bindingHeaders.add("mozilla/dom/ObservableArrayProxyHandler.h")
                else:
                    break
                unrolled = unrolled.inner
            if unrolled.isUnion():
                headerSet.add(self.getUnionDeclarationFilename(config, unrolled))
                for t in unrolled.flatMemberTypes:
                    addHeadersForType((t, None))
            elif unrolled.isPromise():
                # See comment in the isInterface() case for why we add
                # Promise.h to headerSet, not bindingHeaders.
                headerSet.add("mozilla/dom/Promise.h")
                # We need ToJSValue to do the Promise to JS conversion.
                bindingHeaders.add("mozilla/dom/ToJSValue.h")
            elif unrolled.isInterface():
                if unrolled.isSpiderMonkeyInterface():
                    bindingHeaders.add("jsfriendapi.h")
                    if jsImplementedDescriptors:
                        # Since we can't forward-declare typed array types
                        # (because they're typedefs), we have to go ahead and
                        # just include their header if we need to have functions
                        # taking references to them declared in that header.
                        headerSet = declareIncludes
                    headerSet.add("mozilla/dom/TypedArray.h")
                else:
                    try:
                        typeDesc = config.getDescriptor(unrolled.inner.identifier.name)
                    except NoSuchDescriptorError:
                        return
                    # Dictionaries with interface members rely on the
                    # actual class definition of that interface member
                    # being visible in the binding header, because they
                    # store them in RefPtr and have inline
                    # constructors/destructors.
                    #
                    # XXXbz maybe dictionaries with interface members
                    # should just have out-of-line constructors and
                    # destructors?
                    headerSet.add(typeDesc.headerFile)
            elif unrolled.isDictionary():
                headerSet.add(self.getDeclarationFilename(unrolled.inner))
                # And if it needs rooting, we need RootedDictionary too
                if typeNeedsRooting(unrolled):
                    headerSet.add("mozilla/dom/RootedDictionary.h")
            elif unrolled.isCallback():
                headerSet.add(self.getDeclarationFilename(unrolled.callback))
            elif unrolled.isFloat() and not unrolled.isUnrestricted():
                # Restricted floats are tested for finiteness
                bindingHeaders.add("mozilla/FloatingPoint.h")
                bindingHeaders.add("mozilla/dom/PrimitiveConversions.h")
            elif unrolled.isEnum():
                filename = self.getDeclarationFilename(unrolled.inner)
                declareIncludes.add(filename)
            elif unrolled.isPrimitive():
                bindingHeaders.add("mozilla/dom/PrimitiveConversions.h")
            elif unrolled.isRecord():
                if isFromDictionary or jsImplementedDescriptors:
                    declareIncludes.add("mozilla/dom/Record.h")
                else:
                    bindingHeaders.add("mozilla/dom/Record.h")
                # Also add headers for the type the record is
                # parametrized over, if needed.
                addHeadersForType((t.inner, originType if isFromDictionary else None))

        for t in getAllTypes(
            descriptors + callbackDescriptors, dictionaries, callbacks
        ):
            addHeadersForType(t)

        def addHeaderForFunc(func, desc):
            if func is None:
                return
            # Include the right class header, which we can only do
            # if this is a class member function.
            if desc is not None and not desc.headerIsDefault:
                # An explicit header file was provided, assume that we know
                # what we're doing.
                return

            if "::" in func:
                # Strip out the function name and convert "::" to "/"
                bindingHeaders.add("/".join(func.split("::")[:-1]) + ".h")

        # Now for non-callback descriptors make sure we include any
        # headers needed by Func declarations and other things like that.
        for desc in descriptors:
            # If this is an iterator or an async iterator interface generated
            # for a separate iterable interface, skip generating type includes,
            # as we have what we need in IterableIterator.h
            if (
                desc.interface.isIteratorInterface()
                or desc.interface.isAsyncIteratorInterface()
            ):
                continue

            for m in desc.interface.members:
                addHeaderForFunc(PropertyDefiner.getStringAttr(m, "Func"), desc)
                staticTypeOverride = PropertyDefiner.getStringAttr(
                    m, "StaticClassOverride"
                )
                if staticTypeOverride:
                    bindingHeaders.add("/".join(staticTypeOverride.split("::")) + ".h")
            # getExtendedAttribute() returns a list, extract the entry.
            funcList = desc.interface.getExtendedAttribute("Func")
            if funcList is not None:
                addHeaderForFunc(funcList[0], desc)

            if desc.interface.maplikeOrSetlikeOrIterable:
                # We need ToJSValue.h for maplike/setlike type conversions
                bindingHeaders.add("mozilla/dom/ToJSValue.h")
                # Add headers for the key and value types of the
                # maplike/setlike/iterable, since they'll be needed for
                # convenience functions
                if desc.interface.maplikeOrSetlikeOrIterable.hasKeyType():
                    addHeadersForType(
                        (desc.interface.maplikeOrSetlikeOrIterable.keyType, None)
                    )
                if desc.interface.maplikeOrSetlikeOrIterable.hasValueType():
                    addHeadersForType(
                        (desc.interface.maplikeOrSetlikeOrIterable.valueType, None)
                    )

        for d in dictionaries:
            if d.parent:
                declareIncludes.add(self.getDeclarationFilename(d.parent))
            bindingHeaders.add(self.getDeclarationFilename(d))
            for m in d.members:
                addHeaderForFunc(PropertyDefiner.getStringAttr(m, "Func"), None)
            # No need to worry about Func on members of ancestors, because that
            # will happen automatically in whatever files those ancestors live
            # in.

        for c in callbacks:
            bindingHeaders.add(self.getDeclarationFilename(c))

        for c in callbackDescriptors:
            bindingHeaders.add(self.getDeclarationFilename(c.interface))

        if len(callbacks) != 0:
            # We need CallbackFunction to serve as our parent class
            declareIncludes.add("mozilla/dom/CallbackFunction.h")
            # And we need ToJSValue.h so we can wrap "this" objects
            declareIncludes.add("mozilla/dom/ToJSValue.h")

        if len(callbackDescriptors) != 0 or len(jsImplementedDescriptors) != 0:
            # We need CallbackInterface to serve as our parent class
            declareIncludes.add("mozilla/dom/CallbackInterface.h")
            # And we need ToJSValue.h so we can wrap "this" objects
            declareIncludes.add("mozilla/dom/ToJSValue.h")

        # Also need to include the headers for ancestors of
        # JS-implemented interfaces.
        for jsImplemented in jsImplementedDescriptors:
            jsParent = jsImplemented.interface.parent
            if jsParent:
                parentDesc = jsImplemented.getDescriptor(jsParent.identifier.name)
                declareIncludes.add(parentDesc.jsImplParentHeader)

        # Now make sure we're not trying to include the header from inside itself
        declareIncludes.discard(prefix + ".h")

        # Let the machinery do its thing.
        def _includeString(includes):
            def headerName(include):
                # System headers are specified inside angle brackets.
                if include.startswith("<"):
                    return include
                # Non-system headers need to be placed in quotes.
                return '"%s"' % include

            return "".join(["#include %s\n" % headerName(i) for i in includes]) + "\n"

        CGWrapper.__init__(
            self,
            child,
            declarePre=_includeString(sorted(declareIncludes)),
            definePre=_includeString(
                sorted(
                    set(defineIncludes)
                    | bindingIncludes
                    | bindingHeaders
                    | implementationIncludes
                )
            ),
        )

    @staticmethod
    def getDeclarationFilename(decl):
        # Use our local version of the header, not the exported one, so that
        # test bindings, which don't export, will work correctly.
        basename = os.path.basename(decl.filename)
        return basename.replace(".webidl", "Binding.h")

    @staticmethod
    def getUnionDeclarationFilename(config, unionType):
        assert unionType.isUnion()
        assert unionType.unroll() == unionType
        # If a union is "defined" in multiple files, it goes in UnionTypes.h.
        if len(config.filenamesPerUnion[unionType.name]) > 1:
            return "mozilla/dom/UnionTypes.h"
        # If a union is defined by a built-in typedef, it also goes in
        # UnionTypes.h.
        assert len(config.filenamesPerUnion[unionType.name]) == 1
        if "<unknown>" in config.filenamesPerUnion[unionType.name]:
            return "mozilla/dom/UnionTypes.h"
        return CGHeaders.getDeclarationFilename(unionType)


def SortedDictValues(d):
    """
    Returns a list of values from the dict sorted by key.
    """
    return [v for k, v in sorted(d.items())]


def UnionsForFile(config, webIDLFile):
    """
    Returns a list of union types for all union types that are only used in
    webIDLFile. If webIDLFile is None this will return the list of tuples for
    union types that are used in more than one WebIDL file.
    """
    return config.unionsPerFilename.get(webIDLFile, [])


def UnionTypes(unionTypes, config):
    """
    The unionTypes argument should be a list of union types. This is typically
    the list generated by UnionsForFile.

    Returns a tuple containing a set of header filenames to include in
    the header for the types in unionTypes, a set of header filenames to
    include in the implementation file for the types in unionTypes, a set
    of tuples containing a type declaration and a boolean if the type is a
    struct for member types of the union, a list of traverse methods,
    unlink methods and a list of union types. These last three lists only
    contain unique union types.
    """

    headers = set()
    implheaders = set()
    declarations = set()
    unionStructs = dict()
    traverseMethods = dict()
    unlinkMethods = dict()

    for t in unionTypes:
        name = str(t)
        if name not in unionStructs:
            unionStructs[name] = t

            def addHeadersForType(f):
                if f.nullable():
                    headers.add("mozilla/dom/Nullable.h")
                isSequence = f.isSequence()
                if isSequence:
                    # Dealing with sequences requires for-of-compatible
                    # iteration.
                    implheaders.add("js/ForOfIterator.h")
                    # Sequences can always throw "not an object" exceptions.
                    implheaders.add("mozilla/dom/BindingCallContext.h")
                    if typeNeedsRooting(f):
                        headers.add("mozilla/dom/RootedSequence.h")
                f = f.unroll()
                if idlTypeNeedsCallContext(f):
                    implheaders.add("mozilla/dom/BindingCallContext.h")
                if f.isPromise():
                    headers.add("mozilla/dom/Promise.h")
                    # We need ToJSValue to do the Promise to JS conversion.
                    headers.add("mozilla/dom/ToJSValue.h")
                elif f.isInterface():
                    if f.isSpiderMonkeyInterface():
                        headers.add("js/RootingAPI.h")
                        headers.add("js/Value.h")
                        headers.add("mozilla/dom/TypedArray.h")
                    else:
                        try:
                            typeDesc = config.getDescriptor(f.inner.identifier.name)
                        except NoSuchDescriptorError:
                            return
                        if typeDesc.interface.isCallback() or isSequence:
                            # Callback interfaces always use strong refs, so
                            # we need to include the right header to be able
                            # to Release() in our inlined code.
                            #
                            # Similarly, sequences always contain strong
                            # refs, so we'll need the header to handler
                            # those.
                            headers.add(typeDesc.headerFile)
                        elif typeDesc.interface.identifier.name == "WindowProxy":
                            # In UnionTypes.h we need to see the declaration of the
                            # WindowProxyHolder that we use to store the WindowProxy, so
                            # we have its sizeof and know how big to make our union.
                            headers.add(typeDesc.headerFile)
                        else:
                            declarations.add((typeDesc.nativeType, False))
                            implheaders.add(typeDesc.headerFile)
                elif f.isDictionary():
                    # For a dictionary, we need to see its declaration in
                    # UnionTypes.h so we have its sizeof and know how big to
                    # make our union.
                    headers.add(CGHeaders.getDeclarationFilename(f.inner))
                    # And if it needs rooting, we need RootedDictionary too
                    if typeNeedsRooting(f):
                        headers.add("mozilla/dom/RootedDictionary.h")
                elif f.isFloat() and not f.isUnrestricted():
                    # Restricted floats are tested for finiteness
                    implheaders.add("mozilla/FloatingPoint.h")
                    implheaders.add("mozilla/dom/PrimitiveConversions.h")
                elif f.isEnum():
                    # Need to see the actual definition of the enum,
                    # unfortunately.
                    headers.add(CGHeaders.getDeclarationFilename(f.inner))
                elif f.isPrimitive():
                    implheaders.add("mozilla/dom/PrimitiveConversions.h")
                elif f.isCallback():
                    # Callbacks always use strong refs, so we need to include
                    # the right header to be able to Release() in our inlined
                    # code.
                    headers.add(CGHeaders.getDeclarationFilename(f.callback))
                elif f.isRecord():
                    headers.add("mozilla/dom/Record.h")
                    # And add headers for the type we're parametrized over
                    addHeadersForType(f.inner)
                    # And if it needs rooting, we need RootedRecord too
                    if typeNeedsRooting(f):
                        headers.add("mozilla/dom/RootedRecord.h")

            implheaders.add(CGHeaders.getUnionDeclarationFilename(config, t))
            for f in t.flatMemberTypes:
                assert not f.nullable()
                addHeadersForType(f)

            if idlTypeNeedsCycleCollection(t):
                declarations.add(
                    ("mozilla::dom::%s" % CGUnionStruct.unionTypeName(t, True), False)
                )
                traverseMethods[name] = CGCycleCollectionTraverseForOwningUnionMethod(t)
                unlinkMethods[name] = CGCycleCollectionUnlinkForOwningUnionMethod(t)

    # The order of items in CGList is important.
    # Since the union structs friend the unlinkMethods, the forward-declaration
    # for these methods should come before the class declaration. Otherwise
    # some compilers treat the friend declaration as a forward-declaration in
    # the class scope.
    return (
        headers,
        implheaders,
        declarations,
        SortedDictValues(traverseMethods),
        SortedDictValues(unlinkMethods),
        SortedDictValues(unionStructs),
    )


class Argument:
    """
    A class for outputting the type and name of an argument
    """

    def __init__(self, argType, name, default=None):
        self.argType = argType
        self.name = name
        self.default = default

    def declare(self):
        string = self.argType + " " + self.name
        if self.default is not None:
            string += " = " + self.default
        return string

    def define(self):
        return self.argType + " " + self.name


class CGAbstractMethod(CGThing):
    """
    An abstract class for generating code for a method.  Subclasses
    should override definition_body to create the actual code.

    descriptor is the descriptor for the interface the method is associated with

    name is the name of the method as a string

    returnType is the IDLType of the return value

    args is a list of Argument objects

    inline should be True to generate an inline method, whose body is
    part of the declaration.

    alwaysInline should be True to generate an inline method annotated with
    MOZ_ALWAYS_INLINE.

    static should be True to generate a static method, which only has
    a definition.

    If templateArgs is not None it should be a list of strings containing
    template arguments, and the function will be templatized using those
    arguments.

    canRunScript should be True to generate a MOZ_CAN_RUN_SCRIPT annotation.

    signatureOnly should be True to only declare the signature (either in
                  the header, or if static is True in the cpp file).
    """

    def __init__(
        self,
        descriptor,
        name,
        returnType,
        args,
        inline=False,
        alwaysInline=False,
        static=False,
        templateArgs=None,
        canRunScript=False,
        signatureOnly=False,
    ):
        CGThing.__init__(self)
        self.descriptor = descriptor
        self.name = name
        self.returnType = returnType
        self.args = args
        self.inline = inline
        self.alwaysInline = alwaysInline
        self.static = static
        self.templateArgs = templateArgs
        self.canRunScript = canRunScript
        self.signatureOnly = signatureOnly

    def _argstring(self, declare):
        return ", ".join([a.declare() if declare else a.define() for a in self.args])

    def _template(self):
        if self.templateArgs is None:
            return ""
        return "template <%s>\n" % ", ".join(self.templateArgs)

    def _decorators(self):
        decorators = []
        if self.canRunScript:
            decorators.append("MOZ_CAN_RUN_SCRIPT")
        if self.alwaysInline:
            decorators.append("MOZ_ALWAYS_INLINE")
        elif self.inline:
            decorators.append("inline")
        if self.static:
            decorators.append("static")
        decorators.append(self.returnType)
        maybeNewline = " " if self.inline else "\n"
        return " ".join(decorators) + maybeNewline

    def signature(self):
        return "%s%s%s(%s);\n" % (
            self._template(),
            self._decorators(),
            self.name,
            self._argstring(True),
        )

    def declare(self):
        if self.static:
            return ""
        if self.inline:
            return self._define(True)
        return self.signature()

    def indent_body(self, body):
        """
        Indent the code returned by self.definition_body(). Most classes
        simply indent everything two spaces. This is here for
        CGRegisterProtos, which needs custom indentation.
        """
        return indent(body)

    def _define(self, fromDeclare=False):
        return (
            self.definition_prologue(fromDeclare)
            + self.indent_body(self.definition_body())
            + self.definition_epilogue()
        )

    def define(self):
        if self.signatureOnly:
            if self.static:
                # self.static makes us not output anything in the header, so output the signature here.
                return self.signature()
            return ""
        return "" if (self.inline and not self.static) else self._define()

    def definition_prologue(self, fromDeclare):
        error_reporting_label = self.error_reporting_label()
        if error_reporting_label:
            # We're going to want a BindingCallContext.  Rename our JSContext*
            # arg accordingly.
            i = 0
            while i < len(self.args):
                arg = self.args[i]
                if arg.argType == "JSContext*":
                    cxname = arg.name
                    self.args[i] = Argument(arg.argType, "cx_", arg.default)
                    break
                i += 1
            if i == len(self.args):
                raise TypeError("Must have a JSContext* to create a BindingCallContext")

        prologue = "%s%s%s(%s)\n{\n" % (
            self._template(),
            self._decorators(),
            self.name,
            self._argstring(fromDeclare),
        )
        if error_reporting_label:
            prologue += indent(
                fill(
                    """
                BindingCallContext ${cxname}(cx_, ${label});
                """,
                    cxname=cxname,
                    label=error_reporting_label,
                )
            )

        profiler_label = self.auto_profiler_label()
        if profiler_label:
            prologue += indent(profiler_label) + "\n"

        return prologue

    def definition_epilogue(self):
        return "}\n"

    def definition_body(self):
        assert False  # Override me!

    """
    Override this method to return a pair of (descriptive string, name of a
    JSContext* variable) in order to generate a profiler label for this method.
    """

    def auto_profiler_label(self):
        return None  # Override me!

    """
    Override this method to return a string to be used as the label for a
    BindingCallContext.  If this does not return None, one of the arguments of
    this method must be of type 'JSContext*'.  Its name will be replaced with
    'cx_' and a BindingCallContext named 'cx' will be instantiated with the
    given label.
    """

    def error_reporting_label(self):
        return None  # Override me!


class CGAbstractStaticMethod(CGAbstractMethod):
    """
    Abstract base class for codegen of implementation-only (no
    declaration) static methods.
    """

    def __init__(self, descriptor, name, returnType, args, canRunScript=False):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            name,
            returnType,
            args,
            inline=False,
            static=True,
            canRunScript=canRunScript,
        )


class CGAbstractClassHook(CGAbstractStaticMethod):
    """
    Meant for implementing JSClass hooks, like Finalize or Trace. Does very raw
    'this' unwrapping as it assumes that the unwrapped type is always known.
    """

    def __init__(self, descriptor, name, returnType, args):
        CGAbstractStaticMethod.__init__(self, descriptor, name, returnType, args)

    def definition_body_prologue(self):
        return "%s* self = UnwrapPossiblyNotInitializedDOMObject<%s>(obj);\n" % (
            self.descriptor.nativeType,
            self.descriptor.nativeType,
        )

    def definition_body(self):
        return self.definition_body_prologue() + self.generate_code()

    def generate_code(self):
        assert False  # Override me!


class CGAddPropertyHook(CGAbstractClassHook):
    """
    A hook for addProperty, used to preserve our wrapper from GC.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::Handle<JS::Value>", "val"),
        ]
        CGAbstractClassHook.__init__(
            self, descriptor, ADDPROPERTY_HOOK_NAME, "bool", args
        )

    def generate_code(self):
        assert self.descriptor.wrapperCache
        # This hook is also called by TryPreserveWrapper on non-nsISupports
        # cycle collected objects, so if addProperty is ever changed to do
        # anything more or less than preserve the wrapper, TryPreserveWrapper
        # will need to be changed.
        return dedent(
            """
            // We don't want to preserve if we don't have a wrapper, and we
            // obviously can't preserve if we're not initialized.
            if (self && self->GetWrapperPreserveColor()) {
              PreserveWrapper(self);
            }
            return true;
            """
        )


class CGGetWrapperCacheHook(CGAbstractClassHook):
    """
    A hook for GetWrapperCache, used by HasReleasedWrapper to get the
    nsWrapperCache pointer for a non-nsISupports object.
    """

    def __init__(self, descriptor):
        args = [Argument("JS::Handle<JSObject*>", "obj")]
        CGAbstractClassHook.__init__(
            self, descriptor, GETWRAPPERCACHE_HOOK_NAME, "nsWrapperCache*", args
        )

    def generate_code(self):
        assert self.descriptor.wrapperCache
        return dedent(
            """
            return self;
            """
        )


class CGDefineHTMLAttributeSlots(CGThing):
    """
    Function to get the slots object for reflected HTML attributes that return
    a FrozenArray<Element> value.
    """

    def __init__(self, descriptor):
        self.descriptor = descriptor
        CGThing.__init__(self)

    def declare(self):
        atts = self.descriptor.interface.reflectedHTMLAttributesReturningFrozenArray
        return fill(
            """
            using ReflectedHTMLAttributeSlots = binding_detail::ReflectedHTMLAttributeSlots<${slotIndex}, ${xraySlotIndex}, ${arrayLength}>;
            """,
            slotIndex=reservedSlot(atts.slotIndex, False),
            xraySlotIndex=reservedSlot(atts.slotIndex, True),
            arrayLength=atts.totalMembersInSlots,
        )

    def define(self):
        return ""


def finalizeHook(descriptor, hookName, gcx, obj):
    finalize = "JS::SetReservedSlot(%s, DOM_OBJECT_SLOT, JS::UndefinedValue());\n" % obj
    if descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns"):
        finalize += fill(
            """
            // Either our proxy created an expando object or not.  If it did,
            // then we would have preserved ourselves, and hence if we're going
            // away so is our C++ object and we should reset its expando value.
            // It's possible that in this situation the C++ object's reflector
            // pointer has been nulled out, but if not it's pointing to us.  If
            // our proxy did _not_ create an expando object then it's possible
            // that we're no longer the reflector for our C++ object (and
            // incremental finalization is finally getting to us), and that in
            // the meantime the new reflector has created an expando object.
            // In that case we do NOT want to clear the expando pointer in the
            // C++ object.
            //
            // It's important to do this before we ClearWrapper, of course.
            JSObject* reflector = self->GetWrapperMaybeDead();
            if (!reflector || reflector == ${obj}) {
              self->mExpandoAndGeneration.expando = JS::UndefinedValue();
            }
            """,
            obj=obj,
        )
    for m in descriptor.interface.members:
        if m.isAttr() and m.type.isObservableArray():
            finalize += fill(
                """
                {
                  JS::Value val = JS::GetReservedSlot(obj, ${slot});
                  if (!val.isUndefined()) {
                    JSObject* obj = &val.toObject();
                    js::SetProxyReservedSlot(obj, OBSERVABLE_ARRAY_DOM_INTERFACE_SLOT, JS::UndefinedValue());
                  }
                }
                """,
                slot=memberReservedSlot(m, descriptor),
            )
    iface = getReflectedHTMLAttributesIface(descriptor)
    if iface:
        finalize += "%s::ReflectedHTMLAttributeSlots::Finalize(%s);\n" % (
            toBindingNamespace(iface.identifier.name),
            obj,
        )
    if descriptor.wrapperCache:
        finalize += "ClearWrapper(self, self, %s);\n" % obj
    if descriptor.isGlobal():
        finalize += "mozilla::dom::FinalizeGlobal(%s, %s);\n" % (gcx, obj)
    finalize += fill(
        """
        if (size_t mallocBytes = BindingJSObjectMallocBytes(self)) {
          JS::RemoveAssociatedMemory(${obj}, mallocBytes,
                                     JS::MemoryUse::DOMBinding);
        }
        """,
        obj=obj,
    )
    finalize += "AddForDeferredFinalization<%s>(self);\n" % descriptor.nativeType
    return CGIfWrapper(CGGeneric(finalize), "self")


class CGClassFinalizeHook(CGAbstractClassHook):
    """
    A hook for finalize, used to release our native object.
    """

    def __init__(self, descriptor):
        args = [Argument("JS::GCContext*", "gcx"), Argument("JSObject*", "obj")]
        CGAbstractClassHook.__init__(self, descriptor, FINALIZE_HOOK_NAME, "void", args)

    def generate_code(self):
        return finalizeHook(
            self.descriptor, self.name, self.args[0].name, self.args[1].name
        ).define()


def objectMovedHook(descriptor, hookName, obj, old):
    assert descriptor.wrapperCache
    return fill(
        """
        if (self) {
          UpdateWrapper(self, self, ${obj}, ${old});
        }

        return 0;
        """,
        obj=obj,
        old=old,
    )


class CGClassObjectMovedHook(CGAbstractClassHook):
    """
    A hook for objectMovedOp, used to update the wrapper cache when an object it
    is holding moves.
    """

    def __init__(self, descriptor):
        args = [Argument("JSObject*", "obj"), Argument("JSObject*", "old")]
        CGAbstractClassHook.__init__(
            self, descriptor, OBJECT_MOVED_HOOK_NAME, "size_t", args
        )

    def generate_code(self):
        return objectMovedHook(
            self.descriptor, self.name, self.args[0].name, self.args[1].name
        )


def JSNativeArguments():
    return [
        Argument("JSContext*", "cx"),
        Argument("unsigned", "argc"),
        Argument("JS::Value*", "vp"),
    ]


class CGClassConstructor(CGAbstractStaticMethod):
    """
    JS-visible constructor for our objects
    """

    def __init__(self, descriptor, ctor, name=CONSTRUCT_HOOK_NAME):
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", JSNativeArguments()
        )
        self._ctor = ctor

    def define(self):
        if not self._ctor:
            return ""
        return CGAbstractStaticMethod.define(self)

    def definition_body(self):
        return self.generate_code()

    def generate_code(self):
        if self._ctor.isHTMLConstructor():
            # We better have a prototype object.  Otherwise our proto
            # id won't make sense.
            assert self.descriptor.interface.hasInterfacePrototypeObject()
            # We also better have a constructor object, if this is
            # getting called!
            assert self.descriptor.interface.hasInterfaceObject()
            # We can't just pass null for the CreateInterfaceObjects callback,
            # because our newTarget might be in a different compartment, in
            # which case we'll need to look up constructor objects in that
            # compartment.
            return fill(
                """
                return HTMLConstructor(cx, argc, vp,
                                       constructors::id::${name},
                                       prototypes::id::${name},
                                       CreateInterfaceObjects);
                """,
                name=self.descriptor.name,
            )

        # If the interface is already SecureContext, notify getConditionList to skip that check,
        # because the constructor won't be exposed in non-secure contexts to start with.
        alreadySecureContext = self.descriptor.interface.getExtendedAttribute(
            "SecureContext"
        )

        # We want to throw if any of the conditions returned by getConditionList are false.
        conditionsCheck = ""
        rawConditions = getRawConditionList(
            self._ctor, "cx", "obj", alreadySecureContext
        )
        if len(rawConditions) > 0:
            notConditions = " ||\n".join("!" + cond for cond in rawConditions)
            failedCheckAction = CGGeneric("return ThrowingConstructor(cx, argc, vp);\n")
            conditionsCheck = (
                CGIfWrapper(failedCheckAction, notConditions).define() + "\n"
            )

        # Additionally, we want to throw if a caller does a bareword invocation
        # of a constructor without |new|.
        ctorName = GetConstructorNameForReporting(self.descriptor, self._ctor)

        preamble = fill(
            """
            JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
            JS::Rooted<JSObject*> obj(cx, &args.callee());
            $*{conditionsCheck}
            if (!args.isConstructing()) {
              return ThrowConstructorWithoutNew(cx, "${ctorName}");
            }

            JS::Rooted<JSObject*> desiredProto(cx);
            if (!GetDesiredProto(cx, args,
                                 prototypes::id::${name},
                                 CreateInterfaceObjects,
                                 &desiredProto)) {
              return false;
            }
            """,
            conditionsCheck=conditionsCheck,
            ctorName=ctorName,
            name=self.descriptor.name,
        )

        name = self._ctor.identifier.name
        nativeName = MakeNativeName(self.descriptor.binaryNameFor(name, True))
        callGenerator = CGMethodCall(
            nativeName, True, self.descriptor, self._ctor, isConstructor=True
        )
        return preamble + "\n" + callGenerator.define()

    def auto_profiler_label(self):
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${ctorName}", "constructor", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            ctorName=GetConstructorNameForReporting(self.descriptor, self._ctor),
        )

    def error_reporting_label(self):
        return CGSpecializedMethod.error_reporting_label_helper(
            self.descriptor, self._ctor, isConstructor=True
        )


def LegacyFactoryFunctionName(m):
    return "_" + m.identifier.name


class CGLegacyFactoryFunctions(CGThing):
    def __init__(self, descriptor):
        self.descriptor = descriptor
        CGThing.__init__(self)

    def declare(self):
        return ""

    def define(self):
        if len(self.descriptor.interface.legacyFactoryFunctions) == 0:
            return ""

        constructorID = "constructors::id::"
        if self.descriptor.interface.hasInterfaceObject():
            constructorID += self.descriptor.name
        else:
            constructorID += "_ID_Count"

        legacyFactoryFunctions = ""
        for n in self.descriptor.interface.legacyFactoryFunctions:
            legacyFactoryFunctions += (
                '{ "%s", { %s, &sLegacyFactoryFunctionNativePropertyHooks }, %i },\n'
                % (n.identifier.name, LegacyFactoryFunctionName(n), methodLength(n))
            )

        return fill(
            """
            bool sLegacyFactoryFunctionNativePropertiesInited = true;
            const NativePropertyHooks sLegacyFactoryFunctionNativePropertyHooks = {
                nullptr,
                { nullptr, nullptr, &sLegacyFactoryFunctionNativePropertiesInited },
                prototypes::id::${name},
                ${constructorID},
                nullptr
            };

            static const LegacyFactoryFunction legacyFactoryFunctions[] = {
              $*{legacyFactoryFunctions}
            };
            """,
            name=self.descriptor.name,
            constructorID=constructorID,
            legacyFactoryFunctions=legacyFactoryFunctions,
        )


def isChromeOnly(m):
    return m.getExtendedAttribute("ChromeOnly")


def prefIdentifier(pref):
    return pref.replace(".", "_").replace("-", "_")


def prefHeader(pref):
    return "mozilla/StaticPrefs_%s.h" % pref.partition(".")[0]


def computeGlobalNamesFromExposureSet(exposureSet):
    assert exposureSet is None or isinstance(exposureSet, set)

    if exposureSet:
        # Nonempty set
        return " | ".join(map(lambda g: "GlobalNames::%s" % g, sorted(exposureSet)))

    return "0"


class MemberCondition:
    """
    An object representing the condition for a member to actually be
    exposed.  Any of the arguments can be None.  If not
    None, they should have the following types:

    pref: The name of the preference.
    func: The name of the function.
    secureContext: A bool indicating whether a secure context is required.
    nonExposedGlobals: A set of names of globals.  Can be empty, in which case
                       it's treated the same way as None.
    trial: The name of the origin trial.
    """

    def __init__(
        self,
        pref=None,
        func=None,
        secureContext=False,
        nonExposedGlobals=None,
        trial=None,
    ):
        assert pref is None or isinstance(pref, str)
        assert func is None or isinstance(func, str)
        assert trial is None or isinstance(trial, str)
        assert isinstance(secureContext, bool)
        self.pref = pref
        if self.pref:
            identifier = prefIdentifier(self.pref)
            self.prefFuncIndex = "WebIDLPrefIndex::" + identifier
        else:
            self.prefFuncIndex = "WebIDLPrefIndex::NoPref"

        self.secureContext = secureContext

        def toFuncPtr(val):
            if val is None:
                return "nullptr"
            return "&" + val

        self.func = toFuncPtr(func)

        self.nonExposedGlobals = computeGlobalNamesFromExposureSet(nonExposedGlobals)

        if trial:
            self.trial = "OriginTrial::" + trial
        else:
            self.trial = "OriginTrial(0)"

    def __eq__(self, other):
        return (
            self.pref == other.pref
            and self.func == other.func
            and self.secureContext == other.secureContext
            and self.nonExposedGlobals == other.nonExposedGlobals
            and self.trial == other.trial
        )

    def __ne__(self, other):
        return not self.__eq__(other)

    def hasDisablers(self):
        return (
            self.pref is not None
            or self.secureContext
            or self.func != "nullptr"
            or self.nonExposedGlobals != "0"
            or self.trial != "OriginTrial(0)"
        )


class PropertyDefiner:
    """
    A common superclass for defining things on prototype objects.

    Subclasses should implement generateArray to generate the actual arrays of
    things we're defining.  They should also set self.chrome to the list of
    things only exposed to chrome and self.regular to the list of things exposed
    to both chrome and web pages.
    """

    def __init__(self, descriptor, name):
        self.descriptor = descriptor
        self.name = name

    def hasChromeOnly(self):
        return len(self.chrome) > 0

    def hasNonChromeOnly(self):
        return len(self.regular) > 0

    def variableName(self, chrome):
        if chrome:
            if self.hasChromeOnly():
                return "sChrome" + self.name
        else:
            if self.hasNonChromeOnly():
                return "s" + self.name
        return "nullptr"

    def usedForXrays(self):
        return self.descriptor.wantsXrays

    def length(self, chrome):
        return len(self.chrome) if chrome else len(self.regular)

    def __str__(self):
        # We only need to generate id arrays for things that will end
        # up used via ResolveProperty or EnumerateProperties.
        str = self.generateArray(self.regular, self.variableName(False))
        if self.hasChromeOnly():
            str += self.generateArray(self.chrome, self.variableName(True))
        return str

    @staticmethod
    def getStringAttr(member, name):
        attr = member.getExtendedAttribute(name)
        if attr is None:
            return None
        # It's a list of strings
        assert len(attr) == 1
        assert attr[0] is not None
        return attr[0]

    @staticmethod
    def getControllingCondition(interfaceMember, descriptor):
        interface = descriptor.interface
        nonExposureSet = interface.exposureSet - interfaceMember.exposureSet

        trial = PropertyDefiner.getStringAttr(interfaceMember, "Trial")
        if trial and interface.identifier.name in ["Window", "Document"]:
            raise TypeError(
                "[Trial] not yet supported for %s.%s, see bug 1757935"
                % (interface.identifier.name, interfaceMember.identifier.name)
            )

        return MemberCondition(
            PropertyDefiner.getStringAttr(interfaceMember, "Pref"),
            PropertyDefiner.getStringAttr(interfaceMember, "Func"),
            interfaceMember.getExtendedAttribute("SecureContext") is not None,
            nonExposureSet,
            trial,
        )

    @staticmethod
    def generatePrefableArrayValues(
        array,
        descriptor,
        specFormatter,
        specTerminator,
        getCondition,
        getDataTuple,
        switchToCondition=None,
    ):
        """
        This method generates an array of spec entries for interface members. It returns
          a tuple containing the array of spec entries and the maximum of the number of
          spec entries per condition.

        array is an array of interface members.

        descriptor is the descriptor for the interface that array contains members of.

        specFormatter is a function that takes a single argument, a tuple,
          and returns a string, a spec array entry.

        specTerminator is a terminator for the spec array (inserted every time
          our controlling pref changes and at the end of the array).

        getCondition is a callback function that takes an array entry and
          returns the corresponding MemberCondition.

        getDataTuple is a callback function that takes an array entry and
          returns a tuple suitable to be passed to specFormatter.

        switchToCondition is a function that takes a MemberCondition and an array of
          previously generated spec entries. If None is passed for this function then all
          the interface members should return the same value from getCondition.
        """

        def unsupportedSwitchToCondition(condition, specs):
            # If no specs have been added yet then this is just the first call to
            # switchToCondition that we call to avoid putting a specTerminator at the
            # front of the list.
            if len(specs) == 0:
                return
            raise "Not supported"

        if switchToCondition is None:
            switchToCondition = unsupportedSwitchToCondition

        specs = []
        numSpecsInCurPrefable = 0
        maxNumSpecsInPrefable = 0

        # So we won't put a specTerminator at the very front of the list:
        lastCondition = getCondition(array[0], descriptor)

        switchToCondition(lastCondition, specs)

        for member in array:
            curCondition = getCondition(member, descriptor)
            if lastCondition != curCondition:
                # Terminate previous list
                specs.append(specTerminator)
                if numSpecsInCurPrefable > maxNumSpecsInPrefable:
                    maxNumSpecsInPrefable = numSpecsInCurPrefable
                numSpecsInCurPrefable = 0
                # And switch to our new condition
                switchToCondition(curCondition, specs)
                lastCondition = curCondition
            # And the actual spec
            specs.append(specFormatter(getDataTuple(member, descriptor)))
            numSpecsInCurPrefable += 1
        if numSpecsInCurPrefable > maxNumSpecsInPrefable:
            maxNumSpecsInPrefable = numSpecsInCurPrefable
        specs.append(specTerminator)

        return (specs, maxNumSpecsInPrefable)

    def generatePrefableArray(
        self,
        array,
        name,
        specFormatter,
        specTerminator,
        specType,
        getCondition,
        getDataTuple,
    ):
        """
        This method generates our various arrays.

        array is an array of interface members as passed to generateArray

        name is the name as passed to generateArray

        specFormatter is a function that takes a single argument, a tuple,
          and returns a string, a spec array entry

        specTerminator is a terminator for the spec array (inserted every time
          our controlling pref changes and at the end of the array)

        specType is the actual typename of our spec

        getCondition is a callback function that takes an array entry and
          returns the corresponding MemberCondition.

        getDataTuple is a callback function that takes an array entry and
          returns a tuple suitable to be passed to specFormatter.
        """

        # We want to generate a single list of specs, but with specTerminator
        # inserted at every point where the pref name controlling the member
        # changes.  That will make sure the order of the properties as exposed
        # on the interface and interface prototype objects does not change when
        # pref control is added to members while still allowing us to define all
        # the members in the smallest number of JSAPI calls.
        assert len(array) != 0

        disablers = []
        prefableSpecs = []

        disablersTemplate = dedent(
            """
            static const PrefableDisablers %s_disablers%d = {
              %s, %s, %s, %s, %s
            };
            """
        )
        prefableWithDisablersTemplate = "  { &%s_disablers%d, &%s_specs[%d] }"
        prefableWithoutDisablersTemplate = "  { nullptr, &%s_specs[%d] }"

        def switchToCondition(condition, specs):
            # Set up pointers to the new sets of specs inside prefableSpecs
            if condition.hasDisablers():
                prefableSpecs.append(
                    prefableWithDisablersTemplate % (name, len(specs), name, len(specs))
                )
                disablers.append(
                    disablersTemplate
                    % (
                        name,
                        len(specs),
                        condition.prefFuncIndex,
                        condition.nonExposedGlobals,
                        toStringBool(condition.secureContext),
                        condition.trial,
                        condition.func,
                    )
                )
            else:
                prefableSpecs.append(
                    prefableWithoutDisablersTemplate % (name, len(specs))
                )

        specs, maxNumSpecsInPrefable = self.generatePrefableArrayValues(
            array,
            self.descriptor,
            specFormatter,
            specTerminator,
            getCondition,
            getDataTuple,
            switchToCondition,
        )
        prefableSpecs.append("  { nullptr, nullptr }")

        specType = "const " + specType
        arrays = fill(
            """
            MOZ_GLOBINIT static ${specType} ${name}_specs[] = {
            ${specs}
            };

            ${disablers}
            static const Prefable<${specType}> ${name}[] = {
            ${prefableSpecs}
            };

            """,
            specType=specType,
            name=name,
            disablers="\n".join(disablers),
            specs=",\n".join(specs),
            prefableSpecs=",\n".join(prefableSpecs),
        )

        if self.usedForXrays():
            arrays = fill(
                """
                $*{arrays}
                static_assert(${numPrefableSpecs} <= 1ull << NUM_BITS_PROPERTY_INFO_PREF_INDEX,
                    "We have a prefable index that is >= (1 << NUM_BITS_PROPERTY_INFO_PREF_INDEX)");
                static_assert(${maxNumSpecsInPrefable} <= 1ull << NUM_BITS_PROPERTY_INFO_SPEC_INDEX,
                    "We have a spec index that is >= (1 << NUM_BITS_PROPERTY_INFO_SPEC_INDEX)");

                """,
                arrays=arrays,
                # Minus 1 because there's a list terminator in prefableSpecs.
                numPrefableSpecs=len(prefableSpecs) - 1,
                maxNumSpecsInPrefable=maxNumSpecsInPrefable,
            )

        return arrays


# The length of a method is the minimum of the lengths of the
# argument lists of all its overloads.
def overloadLength(arguments):
    i = len(arguments)
    while i > 0 and arguments[i - 1].optional:
        i -= 1
    return i


def methodLength(method):
    signatures = method.signatures()
    return min(overloadLength(arguments) for retType, arguments in signatures)


def clearableCachedAttrs(descriptor):
    return (
        m
        for m in descriptor.interface.members
        if m.isAttr() and
        # Constants should never need clearing!
        m.dependsOn != "Nothing" and m.slotIndices is not None
    )


def MakeClearCachedValueNativeName(member):
    return "ClearCached%sValue" % MakeNativeName(member.identifier.name)


def IDLToCIdentifier(name):
    return name.replace("-", "_")


def EnumerabilityFlags(member):
    if member.getExtendedAttribute("NonEnumerable"):
        return "0"
    return "JSPROP_ENUMERATE"


class MethodDefiner(PropertyDefiner):
    """
    A class for defining methods on a prototype object.
    """

    def __init__(self, descriptor, name, crossOriginOnly, static, unforgeable=False):
        assert not (static and unforgeable)
        PropertyDefiner.__init__(self, descriptor, name)

        # FIXME https://bugzilla.mozilla.org/show_bug.cgi?id=772822
        #       We should be able to check for special operations without an
        #       identifier. For now we check if the name starts with __

        # Ignore non-static methods for interfaces without a proto object
        if descriptor.interface.hasInterfacePrototypeObject() or static:
            methods = [
                m
                for m in descriptor.interface.members
                if m.isMethod()
                and m.isStatic() == static
                and MemberIsLegacyUnforgeable(m, descriptor) == unforgeable
                and (
                    not crossOriginOnly or m.getExtendedAttribute("CrossOriginCallable")
                )
                and not m.isIdentifierLess()
                and not m.getExtendedAttribute("Unexposed")
            ]
        else:
            methods = []
        self.chrome = []
        self.regular = []
        for m in methods:
            method = self.methodData(m, descriptor)

            if m.isStatic():
                method["nativeName"] = CppKeywords.checkMethodName(
                    IDLToCIdentifier(m.identifier.name)
                )

            if isChromeOnly(m):
                self.chrome.append(method)
            else:
                self.regular.append(method)

        # TODO: Once iterable is implemented, use tiebreak rules instead of
        # failing. Also, may be more tiebreak rules to implement once spec bug
        # is resolved.
        # https://www.w3.org/Bugs/Public/show_bug.cgi?id=28592
        def hasIterator(methods, regular):
            return any("@@iterator" in m.aliases for m in methods) or any(
                "@@iterator" == r["name"] for r in regular
            )

        # Check whether we need to output an @@iterator due to having an indexed
        # getter.  We only do this while outputting non-static and
        # non-unforgeable methods, since the @@iterator function will be
        # neither.
        if not static and not unforgeable and descriptor.supportsIndexedProperties():
            if hasIterator(methods, self.regular):
                raise TypeError(
                    "Cannot have indexed getter/attr on "
                    "interface %s with other members "
                    "that generate @@iterator, such as "
                    "maplike/setlike or aliased functions."
                    % self.descriptor.interface.identifier.name
                )
            self.regular.append(
                {
                    "name": "@@iterator",
                    "methodInfo": False,
                    "selfHostedName": "$ArrayValues",
                    "length": 0,
                    "flags": "0",  # Not enumerable, per spec.
                    "condition": MemberCondition(),
                }
            )

        # Generate the keys/values/entries aliases for value iterables.
        maplikeOrSetlikeOrIterable = descriptor.interface.maplikeOrSetlikeOrIterable
        if (
            not static
            and not unforgeable
            and maplikeOrSetlikeOrIterable
            and maplikeOrSetlikeOrIterable.isIterable()
            and maplikeOrSetlikeOrIterable.isValueIterator()
        ):
            # Add our keys/values/entries/forEach
            self.regular.append(
                {
                    "name": "keys",
                    "methodInfo": False,
                    "selfHostedName": "ArrayKeys",
                    "length": 0,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        maplikeOrSetlikeOrIterable, descriptor
                    ),
                }
            )
            self.regular.append(
                {
                    "name": "values",
                    "methodInfo": False,
                    "selfHostedName": "$ArrayValues",
                    "length": 0,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        maplikeOrSetlikeOrIterable, descriptor
                    ),
                }
            )
            self.regular.append(
                {
                    "name": "entries",
                    "methodInfo": False,
                    "selfHostedName": "ArrayEntries",
                    "length": 0,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        maplikeOrSetlikeOrIterable, descriptor
                    ),
                }
            )
            self.regular.append(
                {
                    "name": "forEach",
                    "methodInfo": False,
                    "selfHostedName": "ArrayForEach",
                    "length": 1,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        maplikeOrSetlikeOrIterable, descriptor
                    ),
                }
            )

        if not static:
            stringifier = descriptor.operations["Stringifier"]
            if stringifier and unforgeable == MemberIsLegacyUnforgeable(
                stringifier, descriptor
            ):
                toStringDesc = {
                    "name": GetWebExposedName(stringifier, descriptor),
                    "nativeName": stringifier.identifier.name,
                    "length": 0,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        stringifier, descriptor
                    ),
                }
                if isChromeOnly(stringifier):
                    self.chrome.append(toStringDesc)
                else:
                    self.regular.append(toStringDesc)
            if unforgeable and descriptor.interface.getExtendedAttribute(
                "LegacyUnforgeable"
            ):
                # Synthesize our valueOf method
                self.regular.append(
                    {
                        "name": "valueOf",
                        "selfHostedName": "Object_valueOf",
                        "methodInfo": False,
                        "length": 0,
                        "flags": "0",  # readonly/permanent added automatically.
                        "condition": MemberCondition(),
                    }
                )

        if descriptor.interface.isJSImplemented():
            if static:
                if descriptor.interface.hasInterfaceObject():
                    self.chrome.append(
                        {
                            "name": "_create",
                            "nativeName": ("%s::_Create" % descriptor.name),
                            "methodInfo": False,
                            "length": 2,
                            "flags": "0",
                            "condition": MemberCondition(),
                        }
                    )

        self.unforgeable = unforgeable

        if static:
            if not descriptor.interface.hasInterfaceObject():
                # static methods go on the interface object
                assert not self.hasChromeOnly() and not self.hasNonChromeOnly()
        else:
            if not descriptor.interface.hasInterfacePrototypeObject():
                # non-static methods go on the interface prototype object
                assert not self.hasChromeOnly() and not self.hasNonChromeOnly()

    @staticmethod
    def methodData(m, descriptor, overrideFlags=None):
        return {
            "name": m.identifier.name,
            "methodInfo": not m.isStatic(),
            "length": methodLength(m),
            "flags": (
                EnumerabilityFlags(m) if (overrideFlags is None) else overrideFlags
            ),
            "condition": PropertyDefiner.getControllingCondition(m, descriptor),
            "allowCrossOriginThis": m.getExtendedAttribute("CrossOriginCallable"),
            "returnsPromise": m.returnsPromise(),
            "hasIteratorAlias": "@@iterator" in m.aliases,
        }

    @staticmethod
    def formatSpec(fields):
        if fields[0].startswith("@@"):
            fields = (fields[0][2:],) + fields[1:]
            return "  JS_SYM_FNSPEC(%s, %s, %s, %s, %s, %s)" % fields
        return '  JS_FNSPEC("%s", %s, %s, %s, %s, %s)' % fields

    @staticmethod
    def specData(m, descriptor, unforgeable=False):
        def flags(m, unforgeable):
            unforgeable = " | JSPROP_PERMANENT | JSPROP_READONLY" if unforgeable else ""
            return m["flags"] + unforgeable

        if "selfHostedName" in m:
            selfHostedName = '"%s"' % m["selfHostedName"]
            assert not m.get("methodInfo", True)
            accessor = "nullptr"
            jitinfo = "nullptr"
        else:
            selfHostedName = "nullptr"
            # When defining symbols, function name may not match symbol name
            methodName = m.get("methodName", m["name"])
            accessor = m.get("nativeName", IDLToCIdentifier(methodName))
            if m.get("methodInfo", True):
                if m.get("returnsPromise", False):
                    exceptionPolicy = "ConvertExceptionsToPromises"
                else:
                    exceptionPolicy = "ThrowExceptions"

                # Cast this in case the methodInfo is a
                # JSTypedMethodJitInfo.
                jitinfo = (
                    "reinterpret_cast<const JSJitInfo*>(&%s_methodinfo)" % accessor
                )
                if m.get("allowCrossOriginThis", False):
                    accessor = (
                        "(GenericMethod<CrossOriginThisPolicy, %s>)" % exceptionPolicy
                    )
                elif descriptor.interface.hasDescendantWithCrossOriginMembers:
                    accessor = (
                        "(GenericMethod<MaybeCrossOriginObjectThisPolicy, %s>)"
                        % exceptionPolicy
                    )
                elif descriptor.interface.isOnGlobalProtoChain():
                    accessor = (
                        "(GenericMethod<MaybeGlobalThisPolicy, %s>)" % exceptionPolicy
                    )
                else:
                    accessor = "(GenericMethod<NormalThisPolicy, %s>)" % exceptionPolicy
            else:
                if m.get("returnsPromise", False):
                    jitinfo = "&%s_methodinfo" % accessor
                    accessor = "StaticMethodPromiseWrapper"
                else:
                    jitinfo = "nullptr"

        return (
            m["name"],
            accessor,
            jitinfo,
            m["length"],
            flags(m, unforgeable),
            selfHostedName,
        )

    @staticmethod
    def condition(m, d):
        return m["condition"]

    def generateArray(self, array, name):
        if len(array) == 0:
            return ""

        return self.generatePrefableArray(
            array,
            name,
            self.formatSpec,
            "  JS_FS_END",
            "JSFunctionSpec",
            self.condition,
            functools.partial(self.specData, unforgeable=self.unforgeable),
        )


class AttrDefiner(PropertyDefiner):
    def __init__(self, descriptor, name, crossOriginOnly, static, unforgeable=False):
        assert not (static and unforgeable)
        PropertyDefiner.__init__(self, descriptor, name)
        self.name = name
        # Ignore non-static attributes for interfaces without a proto object
        if descriptor.interface.hasInterfacePrototypeObject() or static:
            idlAttrs = [
                m
                for m in descriptor.interface.members
                if m.isAttr()
                and m.isStatic() == static
                and MemberIsLegacyUnforgeable(m, descriptor) == unforgeable
                and (
                    not crossOriginOnly
                    or m.getExtendedAttribute("CrossOriginReadable")
                    or m.getExtendedAttribute("CrossOriginWritable")
                )
            ]
        else:
            idlAttrs = []

        attributes = []
        for attr in idlAttrs:
            attributes.extend(self.attrData(attr, unforgeable))
        self.chrome = [m for m in attributes if isChromeOnly(m["attr"])]
        self.regular = [m for m in attributes if not isChromeOnly(m["attr"])]
        self.static = static

        if static:
            if not descriptor.interface.hasInterfaceObject():
                # static attributes go on the interface object
                assert not self.hasChromeOnly() and not self.hasNonChromeOnly()
        else:
            if not descriptor.interface.hasInterfacePrototypeObject():
                # non-static attributes go on the interface prototype object
                assert not self.hasChromeOnly() and not self.hasNonChromeOnly()

    @staticmethod
    def attrData(attr, unforgeable=False, overrideFlags=None):
        if overrideFlags is None:
            permanent = " | JSPROP_PERMANENT" if unforgeable else ""
            flags = EnumerabilityFlags(attr) + permanent
        else:
            flags = overrideFlags
        return (
            {"name": name, "attr": attr, "flags": flags}
            for name in [attr.identifier.name] + attr.bindingAliases
        )

    @staticmethod
    def condition(m, d):
        return PropertyDefiner.getControllingCondition(m["attr"], d)

    @staticmethod
    def specData(entry, descriptor, static=False, crossOriginOnly=False):
        def getter(attr):
            if crossOriginOnly and not attr.getExtendedAttribute("CrossOriginReadable"):
                return "nullptr, nullptr"
            if static:
                if attr.type.isPromise():
                    raise TypeError(
                        "Don't know how to handle "
                        "static Promise-returning "
                        "attribute %s.%s" % (descriptor.name, attr.identifier.name)
                    )
                accessor = "get_" + IDLToCIdentifier(attr.identifier.name)
                jitinfo = "nullptr"
            else:
                if attr.type.isPromise():
                    exceptionPolicy = "ConvertExceptionsToPromises"
                else:
                    exceptionPolicy = "ThrowExceptions"

                if attr.hasLegacyLenientThis():
                    if attr.getExtendedAttribute("CrossOriginReadable"):
                        raise TypeError(
                            "Can't handle lenient cross-origin "
                            "readable attribute %s.%s"
                            % (descriptor.name, attr.identifier.name)
                        )
                    if descriptor.interface.hasDescendantWithCrossOriginMembers:
                        accessor = (
                            "GenericGetter<MaybeCrossOriginObjectLenientThisPolicy, %s>"
                            % exceptionPolicy
                        )
                    else:
                        accessor = (
                            "GenericGetter<LenientThisPolicy, %s>" % exceptionPolicy
                        )
                elif attr.getExtendedAttribute("CrossOriginReadable"):
                    accessor = (
                        "GenericGetter<CrossOriginThisPolicy, %s>" % exceptionPolicy
                    )
                elif descriptor.interface.hasDescendantWithCrossOriginMembers:
                    accessor = (
                        "GenericGetter<MaybeCrossOriginObjectThisPolicy, %s>"
                        % exceptionPolicy
                    )
                elif descriptor.interface.isOnGlobalProtoChain():
                    accessor = (
                        "GenericGetter<MaybeGlobalThisPolicy, %s>" % exceptionPolicy
                    )
                else:
                    accessor = "GenericGetter<NormalThisPolicy, %s>" % exceptionPolicy
                jitinfo = "&%s_getterinfo" % IDLToCIdentifier(attr.identifier.name)
            return "%s, %s" % (accessor, jitinfo)

        def setter(attr):
            if (
                attr.readonly
                and attr.getExtendedAttribute("PutForwards") is None
                and attr.getExtendedAttribute("Replaceable") is None
                and attr.getExtendedAttribute("LegacyLenientSetter") is None
            ):
                return "nullptr, nullptr"
            if crossOriginOnly and not attr.getExtendedAttribute("CrossOriginWritable"):
                return "nullptr, nullptr"
            if static:
                accessor = "set_" + IDLToCIdentifier(attr.identifier.name)
                jitinfo = "nullptr"
            else:
                if attr.hasLegacyLenientThis():
                    if attr.getExtendedAttribute("CrossOriginWritable"):
                        raise TypeError(
                            "Can't handle lenient cross-origin "
                            "writable attribute %s.%s"
                            % (descriptor.name, attr.identifier.name)
                        )
                    if descriptor.interface.hasDescendantWithCrossOriginMembers:
                        accessor = (
                            "GenericSetter<MaybeCrossOriginObjectLenientThisPolicy>"
                        )
                    else:
                        accessor = "GenericSetter<LenientThisPolicy>"
                elif attr.getExtendedAttribute("CrossOriginWritable"):
                    accessor = "GenericSetter<CrossOriginThisPolicy>"
                elif descriptor.interface.hasDescendantWithCrossOriginMembers:
                    accessor = "GenericSetter<MaybeCrossOriginObjectThisPolicy>"
                elif descriptor.interface.isOnGlobalProtoChain():
                    accessor = "GenericSetter<MaybeGlobalThisPolicy>"
                else:
                    accessor = "GenericSetter<NormalThisPolicy>"
                jitinfo = "&%s_setterinfo" % IDLToCIdentifier(attr.identifier.name)
            return "%s, %s" % (accessor, jitinfo)

        name, attr, flags = entry["name"], entry["attr"], entry["flags"]
        return (name, flags, getter(attr), setter(attr))

    @staticmethod
    def formatSpec(fields):
        return '  JSPropertySpec::nativeAccessors("%s", %s, %s, %s)' % fields

    def generateArray(self, array, name):
        if len(array) == 0:
            return ""

        return self.generatePrefableArray(
            array,
            name,
            self.formatSpec,
            "  JS_PS_END",
            "JSPropertySpec",
            self.condition,
            functools.partial(self.specData, static=self.static),
        )


class ConstDefiner(PropertyDefiner):
    """
    A class for definining constants on the interface object
    """

    def __init__(self, descriptor, name):
        PropertyDefiner.__init__(self, descriptor, name)
        self.name = name
        constants = [m for m in descriptor.interface.members if m.isConst()]
        self.chrome = [m for m in constants if isChromeOnly(m)]
        self.regular = [m for m in constants if not isChromeOnly(m)]

    def generateArray(self, array, name):
        if len(array) == 0:
            return ""

        def specData(const, descriptor):
            return (const.identifier.name, convertConstIDLValueToJSVal(const.value))

        return self.generatePrefableArray(
            array,
            name,
            lambda fields: '  { "%s", %s }' % fields,
            "  { 0, JS::UndefinedValue() }",
            "ConstantSpec",
            PropertyDefiner.getControllingCondition,
            specData,
        )


class PropertyArrays:
    def __init__(self, descriptor, crossOriginOnly=False):
        self.staticMethods = MethodDefiner(
            descriptor, "StaticMethods", crossOriginOnly, static=True
        )
        self.staticAttrs = AttrDefiner(
            descriptor, "StaticAttributes", crossOriginOnly, static=True
        )
        self.methods = MethodDefiner(
            descriptor, "Methods", crossOriginOnly, static=False
        )
        self.attrs = AttrDefiner(
            descriptor, "Attributes", crossOriginOnly, static=False
        )
        self.unforgeableMethods = MethodDefiner(
            descriptor,
            "UnforgeableMethods",
            crossOriginOnly,
            static=False,
            unforgeable=True,
        )
        self.unforgeableAttrs = AttrDefiner(
            descriptor,
            "UnforgeableAttributes",
            crossOriginOnly,
            static=False,
            unforgeable=True,
        )
        self.consts = ConstDefiner(descriptor, "Constants")

    @staticmethod
    def arrayNames():
        return [
            "staticMethods",
            "staticAttrs",
            "methods",
            "attrs",
            "unforgeableMethods",
            "unforgeableAttrs",
            "consts",
        ]

    def hasChromeOnly(self):
        return any(getattr(self, a).hasChromeOnly() for a in self.arrayNames())

    def hasNonChromeOnly(self):
        return any(getattr(self, a).hasNonChromeOnly() for a in self.arrayNames())

    def __str__(self):
        define = ""
        for array in self.arrayNames():
            define += str(getattr(self, array))
        return define


class CGConstDefinition(CGThing):
    """
    Given a const member of an interface, return the C++ static const definition
    for the member. Should be part of the interface namespace in the header
    file.
    """

    def __init__(self, member):
        assert (
            member.isConst()
            and member.value.type.isPrimitive()
            and not member.value.type.nullable()
        )

        name = CppKeywords.checkMethodName(IDLToCIdentifier(member.identifier.name))
        tag = member.value.type.tag()
        value = member.value.value
        if tag == IDLType.Tags.bool:
            value = toStringBool(member.value.value)
        self.const = "static const %s %s = %s;" % (builtinNames[tag], name, value)

    def declare(self):
        return self.const

    def define(self):
        return ""

    def deps(self):
        return []


class CGNativeProperties(CGList):
    def __init__(self, descriptor, properties):
        def generateNativeProperties(name, chrome):
            def check(p):
                return p.hasChromeOnly() if chrome else p.hasNonChromeOnly()

            nativePropsInts = []
            nativePropsPtrs = []
            nativePropsDuos = []

            duosOffset = 0
            idsOffset = 0
            for array in properties.arrayNames():
                propertyArray = getattr(properties, array)
                if check(propertyArray):
                    varName = propertyArray.variableName(chrome)
                    bitfields = "true,  %d /* %s */" % (duosOffset, varName)
                    duosOffset += 1
                    nativePropsInts.append(CGGeneric(bitfields))

                    if propertyArray.usedForXrays():
                        ids = "&%s_propertyInfos[%d]" % (name, idsOffset)
                        idsOffset += propertyArray.length(chrome)
                    else:
                        ids = "nullptr"
                    duo = "{ %s, %s }" % (varName, ids)
                    nativePropsDuos.append(CGGeneric(duo))
                else:
                    bitfields = "false, 0"
                    nativePropsInts.append(CGGeneric(bitfields))

            iteratorAliasIndex = -1
            for index, item in enumerate(properties.methods.regular):
                if item.get("hasIteratorAlias"):
                    iteratorAliasIndex = index
                    break
            nativePropsInts.append(CGGeneric(str(iteratorAliasIndex)))

            nativePropsDuos = [
                CGWrapper(
                    CGIndenter(CGList(nativePropsDuos, ",\n")), pre="{\n", post="\n}"
                )
            ]

            pre = "static const NativePropertiesN<%d> %s = {\n" % (duosOffset, name)
            post = "\n};\n"
            if descriptor.wantsXrays:
                pre = fill(
                    """
                    static uint16_t ${name}_sortedPropertyIndices[${size}];
                    static PropertyInfo ${name}_propertyInfos[${size}];

                    $*{pre}
                    """,
                    name=name,
                    size=idsOffset,
                    pre=pre,
                )
                if iteratorAliasIndex > 0:
                    # The iteratorAliasMethodIndex is a signed integer, so the
                    # max value it can store is 2^(nbits-1)-1.
                    post = fill(
                        """
                        $*{post}
                        static_assert(${iteratorAliasIndex} < 1ull << (CHAR_BIT * sizeof(${name}.iteratorAliasMethodIndex) - 1),
                            "We have an iterator alias index that is oversized");
                        """,
                        post=post,
                        iteratorAliasIndex=iteratorAliasIndex,
                        name=name,
                    )
                post = fill(
                    """
                    $*{post}
                    static_assert(${propertyInfoCount} < 1ull << (CHAR_BIT * sizeof(${name}.propertyInfoCount)),
                        "We have a property info count that is oversized");
                    """,
                    post=post,
                    propertyInfoCount=idsOffset,
                    name=name,
                )
                nativePropsInts.append(CGGeneric("%d" % idsOffset))
                nativePropsPtrs.append(CGGeneric("%s_sortedPropertyIndices" % name))
            else:
                nativePropsInts.append(CGGeneric("0"))
                nativePropsPtrs.append(CGGeneric("nullptr"))
            nativeProps = nativePropsInts + nativePropsPtrs + nativePropsDuos
            return CGWrapper(CGIndenter(CGList(nativeProps, ",\n")), pre=pre, post=post)

        nativeProperties = []
        if properties.hasNonChromeOnly():
            nativeProperties.append(
                generateNativeProperties("sNativeProperties", False)
            )
        if properties.hasChromeOnly():
            nativeProperties.append(
                generateNativeProperties("sChromeOnlyNativeProperties", True)
            )

        CGList.__init__(self, nativeProperties, "\n")

    def declare(self):
        return ""

    def define(self):
        return CGList.define(self)


class CGCollectJSONAttributesMethod(CGAbstractMethod):
    """
    Generate the CollectJSONAttributes method for an interface descriptor
    """

    def __init__(self, descriptor, toJSONMethod):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("%s*" % descriptor.nativeType, "self"),
            Argument("JS::Rooted<JSObject*>&", "result"),
        ]
        CGAbstractMethod.__init__(
            self, descriptor, "CollectJSONAttributes", "bool", args, canRunScript=True
        )
        self.toJSONMethod = toJSONMethod

    def definition_body(self):
        ret = ""
        interface = self.descriptor.interface
        toJSONCondition = PropertyDefiner.getControllingCondition(
            self.toJSONMethod, self.descriptor
        )
        needUnwrappedObj = False
        for m in interface.members:
            if m.isAttr() and not m.isStatic() and m.type.isJSONType():
                getAndDefine = fill(
                    """
                    JS::Rooted<JS::Value> temp(cx);
                    if (!get_${name}(cx, obj, self, JSJitGetterCallArgs(&temp))) {
                      return false;
                    }
                    if (!JS_DefineProperty(cx, result, "${name}", temp, JSPROP_ENUMERATE)) {
                      return false;
                    }
                    """,
                    name=IDLToCIdentifier(m.identifier.name),
                )
                # Make sure we don't include things which are supposed to be
                # disabled.  Things that either don't have disablers or whose
                # disablers match the disablers for our toJSON method can't
                # possibly be disabled, but other things might be.
                condition = PropertyDefiner.getControllingCondition(m, self.descriptor)
                if condition.hasDisablers() and condition != toJSONCondition:
                    needUnwrappedObj = True
                    ret += fill(
                        """
                        // This is unfortunately a linear scan through sAttributes, but we
                        // only do it for things which _might_ be disabled, which should
                        // help keep the performance problems down.
                        if (IsGetterEnabled(cx, unwrappedObj, (JSJitGetterOp)get_${name}, sAttributes)) {
                          $*{getAndDefine}
                        }
                        """,
                        name=IDLToCIdentifier(m.identifier.name),
                        getAndDefine=getAndDefine,
                    )
                else:
                    ret += fill(
                        """
                        { // scope for "temp"
                          $*{getAndDefine}
                        }
                        """,
                        getAndDefine=getAndDefine,
                    )
        ret += "return true;\n"

        if needUnwrappedObj:
            # If we started allowing cross-origin objects here, we'd need to
            # use CheckedUnwrapDynamic and figure out whether it makes sense.
            # But in practice no one is trying to add toJSON methods to those,
            # so let's just guard against it.
            assert not self.descriptor.isMaybeCrossOriginObject()
            ret = fill(
                """
                JS::Rooted<JSObject*> unwrappedObj(cx, js::CheckedUnwrapStatic(obj));
                if (!unwrappedObj) {
                  // How did that happen?  We managed to get called with that
                  // object as "this"!  Just give up on sanity.
                  return false;
                }

                $*{ret}
                """,
                ret=ret,
            )

        return ret


class CGCreateInterfaceObjectsMethod(CGAbstractMethod):
    """
    Generate the CreateInterfaceObjects method for an interface descriptor.

    properties should be a PropertyArrays instance.
    """

    def __init__(
        self, descriptor, properties, haveUnscopables, haveLegacyWindowAliases, static
    ):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("JS::Handle<JSObject*>", "aGlobal"),
            Argument("ProtoAndIfaceCache&", "aProtoAndIfaceCache"),
            Argument("DefineInterfaceProperty", "aDefineOnGlobal"),
        ]
        CGAbstractMethod.__init__(
            self, descriptor, "CreateInterfaceObjects", "void", args, static=static
        )
        self.properties = properties
        self.haveUnscopables = haveUnscopables
        self.haveLegacyWindowAliases = haveLegacyWindowAliases

    def definition_body(self):
        needInterfaceObject = self.descriptor.interface.hasInterfaceObject()
        if needInterfaceObject and self.descriptor.isExposedConditionally():
            # This code might be called when we're trying to create an object
            # in a non-system compartment, for example when system code is
            # calling a constructor through Xrays. In that case we do want to
            # create an interface object in the non-system compartment, but we
            # don't want to expose the name on the non-system global if the
            # interface itself is marked as ChromeOnly.
            defineOnGlobal = (
                "ShouldExpose<%s::ConstructorEnabled>(aCx, aGlobal, aDefineOnGlobal)"
                % toBindingNamespace(self.descriptor.name)
            )
        else:
            defineOnGlobal = "aDefineOnGlobal != DefineInterfaceProperty::No"
        if needInterfaceObject:
            if self.descriptor.interface.isNamespace():
                if self.descriptor.interface.getExtendedAttribute("ProtoObjectHack"):
                    getConstructorProto = "GetHackedNamespaceProtoObject"
                else:
                    getConstructorProto = "JS::GetRealmObjectPrototype"
                getConstructorProto = "aCx, " + getConstructorProto
                constructorProtoType = "Rooted"
            else:
                getConstructorProto = InterfaceObjectProtoGetter(self.descriptor)
                constructorProtoType = "Handle"

            getConstructorProto = fill(
                """
                JS::${type}<JSObject*> constructorProto(${getConstructorProto}(aCx));
                if (!constructorProto) {
                  return;
                }
                """,
                type=constructorProtoType,
                getConstructorProto=getConstructorProto,
            )

            interfaceInfo = "&sInterfaceObjectInfo"
            interfaceCache = (
                "&aProtoAndIfaceCache.EntrySlotOrCreate(constructors::id::%s)"
                % self.descriptor.name
            )
            getConstructorProto = CGGeneric(getConstructorProto)
            constructorProto = "constructorProto"
        else:
            # We don't have slots to store the legacy factory functions.
            assert len(self.descriptor.interface.legacyFactoryFunctions) == 0
            interfaceInfo = "nullptr"
            interfaceCache = "nullptr"
            getConstructorProto = None
            constructorProto = "nullptr"

        if self.properties.hasNonChromeOnly():
            properties = "sNativeProperties.Upcast()"
        else:
            properties = "nullptr"
        if self.properties.hasChromeOnly():
            chromeProperties = "sChromeOnlyNativeProperties.Upcast()"
        else:
            chromeProperties = "nullptr"

        # We use getClassName here. This should be the right thing to pass as
        # the name argument to CreateInterfaceObjects. This is generally the
        # interface identifier, except for the synthetic interfaces created for
        # the default iterator objects. If needInterfaceObject is true then
        # we'll use the name to install a property on the global object, so
        # there shouldn't be any spaces in the name.
        name = self.descriptor.interface.getClassName()
        assert not (needInterfaceObject and " " in name)

        if self.descriptor.interface.isNamespace():
            # If we don't need to create anything, why are we generating this?
            assert needInterfaceObject

            call = fill(
                """
                JS::Heap<JSObject*>* interfaceCache = ${interfaceCache};
                dom::CreateNamespaceObject(aCx, aGlobal, ${constructorProto},
                                           sNamespaceObjectClass,
                                           interfaceCache,
                                           ${properties},
                                           ${chromeProperties},
                                           "${name}",
                                           ${defineOnGlobal});
                """,
                interfaceCache=interfaceCache,
                constructorProto=constructorProto,
                properties=properties,
                chromeProperties=chromeProperties,
                name=name,
                defineOnGlobal=defineOnGlobal,
            )
            return CGList(
                [
                    getConstructorProto,
                    CGGeneric(call),
                ],
                "\n",
            ).define()

        needInterfacePrototypeObject = (
            self.descriptor.interface.hasInterfacePrototypeObject()
        )

        # If we don't need to create anything, why are we generating this?
        assert needInterfaceObject or needInterfacePrototypeObject

        if needInterfacePrototypeObject:
            (protoGetter, protoHandleGetter) = InterfacePrototypeObjectProtoGetter(
                self.descriptor
            )
            if protoHandleGetter is None:
                parentProtoType = "Rooted"
                getParentProto = "aCx, " + protoGetter
            else:
                parentProtoType = "Handle"
                getParentProto = protoHandleGetter

            getParentProto = fill(
                """
                JS::${type}<JSObject*> parentProto(${getParentProto}(aCx));
                if (!parentProto) {
                  return;
                }
                """,
                type=parentProtoType,
                getParentProto=getParentProto,
            )

            protoClass = "&sPrototypeClass"
            protoCache = (
                "&aProtoAndIfaceCache.EntrySlotOrCreate(prototypes::id::%s)"
                % self.descriptor.name
            )
            parentProto = "parentProto"
            getParentProto = CGGeneric(getParentProto)
        else:
            protoClass = "nullptr"
            protoCache = "nullptr"
            parentProto = "nullptr"
            getParentProto = None

        if self.descriptor.interface.ctor():
            constructArgs = methodLength(self.descriptor.interface.ctor())
            isConstructorChromeOnly = isChromeOnly(self.descriptor.interface.ctor())
        else:
            constructArgs = 0
            isConstructorChromeOnly = False
        if len(self.descriptor.interface.legacyFactoryFunctions) > 0:
            legacyFactoryFunctions = "Span(legacyFactoryFunctions)"
        else:
            legacyFactoryFunctions = "Span<const LegacyFactoryFunction, 0>{}"

        isGlobal = self.descriptor.isGlobal() is not None

        ensureCaches = fill(
            """
            JS::Heap<JSObject*>* protoCache = ${protoCache};
            JS::Heap<JSObject*>* interfaceCache = ${interfaceCache};
            """,
            protoCache=protoCache,
            interfaceCache=interfaceCache,
        )
        call = fill(
            """
            dom::CreateInterfaceObjects(aCx, aGlobal, ${parentProto},
                                        ${protoClass}, protoCache,
                                        ${constructorProto}, ${interfaceInfo}, ${constructArgs}, ${isConstructorChromeOnly}, ${legacyFactoryFunctions},
                                        interfaceCache,
                                        ${properties},
                                        ${chromeProperties},
                                        "${name}",
                                        ${defineOnGlobal},
                                        ${unscopableNames},
                                        ${isGlobal},
                                        ${legacyWindowAliases});
            """,
            protoClass=protoClass,
            parentProto=parentProto,
            constructorProto=constructorProto,
            interfaceInfo=interfaceInfo,
            constructArgs=constructArgs,
            isConstructorChromeOnly=toStringBool(isConstructorChromeOnly),
            legacyFactoryFunctions=legacyFactoryFunctions,
            properties=properties,
            chromeProperties=chromeProperties,
            name=name,
            defineOnGlobal=defineOnGlobal,
            unscopableNames="unscopableNames" if self.haveUnscopables else "nullptr",
            isGlobal=toStringBool(isGlobal),
            legacyWindowAliases=(
                "legacyWindowAliases" if self.haveLegacyWindowAliases else "nullptr"
            ),
        )

        # If we fail after here, we must clear interface and prototype caches
        # using this code: intermediate failure must not expose the interface in
        # partially-constructed state.  Note that every case after here needs an
        # interface prototype object.
        failureCode = dedent(
            """
            *protoCache = nullptr;
            if (interfaceCache) {
              *interfaceCache = nullptr;
            }
            return;
            """
        )

        needProtoVar = False

        aliasedMembers = [
            m for m in self.descriptor.interface.members if m.isMethod() and m.aliases
        ]
        if aliasedMembers:
            assert needInterfacePrototypeObject

            def defineAlias(alias):
                if alias == "@@iterator" or alias == "@@asyncIterator":
                    name = alias[2:]

                    symbolJSID = (
                        "JS::GetWellKnownSymbolKey(aCx, JS::SymbolCode::%s)" % name
                    )
                    prop = "%sId" % name
                    getSymbolJSID = CGGeneric(
                        fill(
                            "JS::Rooted<jsid> ${prop}(aCx, ${symbolJSID});",
                            prop=prop,
                            symbolJSID=symbolJSID,
                        )
                    )
                    defineFn = "JS_DefinePropertyById"
                    enumFlags = "0"  # Not enumerable, per spec.
                elif alias.startswith("@@"):
                    raise TypeError(
                        "Can't handle any well-known Symbol other than @@iterator and @@asyncIterator"
                    )
                else:
                    getSymbolJSID = None
                    defineFn = "JS_DefineProperty"
                    prop = '"%s"' % alias
                    # XXX If we ever create non-enumerable properties that can
                    #     be aliased, we should consider making the aliases
                    #     match the enumerability of the property being aliased.
                    enumFlags = "JSPROP_ENUMERATE"
                return CGList(
                    [
                        getSymbolJSID,
                        CGGeneric(
                            fill(
                                """
                        if (!${defineFn}(aCx, proto, ${prop}, aliasedVal, ${enumFlags})) {
                          $*{failureCode}
                        }
                        """,
                                defineFn=defineFn,
                                prop=prop,
                                enumFlags=enumFlags,
                                failureCode=failureCode,
                            )
                        ),
                    ],
                    "\n",
                )

            def defineAliasesFor(m):
                return CGList(
                    [
                        CGGeneric(
                            fill(
                                """
                        if (!JS_GetProperty(aCx, proto, \"${prop}\", &aliasedVal)) {
                          $*{failureCode}
                        }
                        """,
                                failureCode=failureCode,
                                prop=m.identifier.name,
                            )
                        )
                    ]
                    + [defineAlias(alias) for alias in sorted(m.aliases)]
                )

            defineAliases = CGList(
                [
                    CGGeneric(
                        dedent(
                            """
                    // Set up aliases on the interface prototype object we just created.
                    """
                        )
                    ),
                    CGGeneric("JS::Rooted<JS::Value> aliasedVal(aCx);\n\n"),
                ]
                + [
                    defineAliasesFor(m)
                    for m in sorted(aliasedMembers, key=lambda m: m.identifier.name)
                ]
            )
            needProtoVar = True
        else:
            defineAliases = None

        # Globals handle unforgeables directly in Wrap() instead of
        # via a holder.
        if (
            self.descriptor.hasLegacyUnforgeableMembers
            and not self.descriptor.isGlobal()
        ):
            assert needInterfacePrototypeObject

            # We want to use the same JSClass and prototype as the object we'll
            # end up defining the unforgeable properties on in the end, so that
            # we can use JS_InitializePropertiesFromCompatibleNativeObject to do
            # a fast copy.  In the case of proxies that's null, because the
            # expando object is a vanilla object, but in the case of other DOM
            # objects it's whatever our class is.
            if self.descriptor.proxy:
                holderClass = "nullptr"
                holderProto = "nullptr"
            else:
                holderClass = "sClass.ToJSClass()"
                holderProto = "proto"
                needProtoVar = True
            createUnforgeableHolder = CGGeneric(
                fill(
                    """
                JS::Rooted<JSObject*> unforgeableHolder(
                    aCx, JS_NewObjectWithoutMetadata(aCx, ${holderClass}, ${holderProto}));
                if (!unforgeableHolder) {
                  $*{failureCode}
                }
                """,
                    holderProto=holderProto,
                    holderClass=holderClass,
                    failureCode=failureCode,
                )
            )
            defineUnforgeables = InitUnforgeablePropertiesOnHolder(
                self.descriptor, self.properties, failureCode
            )
            createUnforgeableHolder = CGList(
                [createUnforgeableHolder, defineUnforgeables]
            )

            installUnforgeableHolder = CGGeneric(
                dedent(
                    """
                if (*protoCache) {
                  JS::SetReservedSlot(*protoCache, DOM_INTERFACE_PROTO_SLOTS_BASE,
                                      JS::ObjectValue(*unforgeableHolder));
                }
                """
                )
            )

            unforgeableHolderSetup = CGList(
                [createUnforgeableHolder, installUnforgeableHolder], "\n"
            )
        else:
            unforgeableHolderSetup = None

        if (
            self.descriptor.interface.isOnGlobalProtoChain()
            and needInterfacePrototypeObject
        ):
            makeProtoPrototypeImmutable = CGGeneric(
                fill(
                    """
                {
                  bool succeeded;
                  if (!JS_SetImmutablePrototype(aCx, proto, &succeeded)) {
                    $*{failureCode}
                  }

                  MOZ_ASSERT(succeeded,
                             "making a fresh prototype object's [[Prototype]] "
                             "immutable can internally fail, but it should "
                             "never be unsuccessful");
                }
                """,
                    protoCache=protoCache,
                    failureCode=failureCode,
                )
            )
            needProtoVar = True
        else:
            makeProtoPrototypeImmutable = None

        if needProtoVar:
            defineProtoVar = CGGeneric(
                fill(
                    """
                JS::AssertObjectIsNotGray(*protoCache);
                JS::Handle<JSObject*> proto = JS::Handle<JSObject*>::fromMarkedLocation(protoCache->unsafeAddress());
                if (!proto) {
                  $*{failureCode}
                }
                """,
                    failureCode=failureCode,
                )
            )
        else:
            defineProtoVar = None

        # ensureCaches needs to come first as it crashes on failure (like OOM).
        # We want to make sure that the caches do exist before we try to return
        # to the caller, so it can rely on that (and detect other failures by
        # checking for null in the caches).
        return CGList(
            [
                CGGeneric(ensureCaches),
                getParentProto,
                getConstructorProto,
                CGGeneric(call),
                defineProtoVar,
                defineAliases,
                unforgeableHolderSetup,
                makeProtoPrototypeImmutable,
            ],
            "\n",
        ).define()


class CGCreateAndDefineOnGlobalMethod(CGAbstractMethod):
    """
    A method for creating the interface or namespace object and defining
    properties for it on the global.
    """

    def __init__(self, descriptor):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "CreateAndDefineOnGlobal",
            "bool",
            [
                Argument("JSContext*", "aCx"),
            ],
            inline=True,
        )

    def definition_body(self):
        return fill(
            """
            // Get the interface or namespace object for this class. This will
            // create the object as needed and always define the properties for
            // it on the global. The caller should make sure the interface or
            // namespace is exposed on the global before calling this.
            return GetPerInterfaceObjectHandle(aCx, constructors::id::${name},
                                               &CreateInterfaceObjects,
                                               DefineInterfaceProperty::Always);

            """,
            name=self.descriptor.name,
        )


class CGGetProtoObjectHandleMethod(CGAbstractMethod):
    """
    A method for getting the interface prototype object.
    """

    def __init__(self, descriptor, static, signatureOnly=False):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "GetProtoObjectHandle",
            "JS::Handle<JSObject*>",
            [Argument("JSContext*", "aCx")],
            static=static,
            signatureOnly=signatureOnly,
        )

    def definition_body(self):
        return fill(
            """
            /* Get the interface prototype object for this class.  This will create the
               object as needed. */
            return GetPerInterfaceObjectHandle(aCx, prototypes::id::${name},
                                               &CreateInterfaceObjects,
                                               DefineInterfaceProperty::CheckExposure);

            """,
            name=self.descriptor.name,
        )


class CGGetProtoObjectMethod(CGAbstractMethod):
    """
    A method for getting the interface prototype object.
    """

    def __init__(self, descriptor):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "GetProtoObject",
            "JSObject*",
            [Argument("JSContext*", "aCx")],
        )

    def definition_body(self):
        return "return GetProtoObjectHandle(aCx);\n"


class CGGetConstructorObjectHandleMethod(CGAbstractMethod):
    """
    A method for getting the interface constructor object.
    """

    def __init__(self, descriptor):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "GetConstructorObjectHandle",
            "JS::Handle<JSObject*>",
            [
                Argument("JSContext*", "aCx"),
            ],
        )

    def definition_body(self):
        return fill(
            """
            /* Get the interface object for this class.  This will create the object as
               needed. */

            return GetPerInterfaceObjectHandle(aCx, constructors::id::${name},
                                               &CreateInterfaceObjects,
                                               DefineInterfaceProperty::CheckExposure);
            """,
            name=self.descriptor.name,
        )


class CGGetNamedPropertiesObjectMethod(CGAbstractStaticMethod):
    def __init__(self, descriptor):
        args = [Argument("JSContext*", "aCx")]
        CGAbstractStaticMethod.__init__(
            self, descriptor, "GetNamedPropertiesObject", "JSObject*", args
        )

    def definition_body(self):
        parentProtoName = self.descriptor.parentPrototypeName
        if parentProtoName is None:
            getParentProto = ""
            parentProto = "nullptr"
        else:
            getParentProto = fill(
                """
                JS::Rooted<JSObject*> parentProto(aCx, ${parent}::GetProtoObjectHandle(aCx));
                if (!parentProto) {
                  return nullptr;
                }
                """,
                parent=toBindingNamespace(parentProtoName),
            )
            parentProto = "parentProto"
        return fill(
            """
            /* Make sure our global is sane.  Hopefully we can remove this sometime */
            JSObject* global = JS::CurrentGlobalOrNull(aCx);
            if (!(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL)) {
              return nullptr;
            }

            /* Check to see whether the named properties object has already been created */
            ProtoAndIfaceCache& protoAndIfaceCache = *GetProtoAndIfaceCache(global);

            JS::Heap<JSObject*>& namedPropertiesObject = protoAndIfaceCache.EntrySlotOrCreate(namedpropertiesobjects::id::${ifaceName});
            if (!namedPropertiesObject) {
              $*{getParentProto}
              namedPropertiesObject = ${nativeType}::CreateNamedPropertiesObject(aCx, ${parentProto});
              DebugOnly<const DOMIfaceAndProtoJSClass*> clasp =
                DOMIfaceAndProtoJSClass::FromJSClass(JS::GetClass(namedPropertiesObject));
              MOZ_ASSERT(clasp->mType == eNamedPropertiesObject,
                         "Expected ${nativeType}::CreateNamedPropertiesObject to return a named properties object");
              MOZ_ASSERT(clasp->mNativeHooks,
                         "The named properties object for ${nativeType} should have NativePropertyHooks.");
              MOZ_ASSERT(!clasp->mNativeHooks->mIndexedOrNamedNativeProperties ||
                         !clasp->mNativeHooks->mIndexedOrNamedNativeProperties->mResolveOwnProperty,
                         "Shouldn't resolve the properties of the named properties object for ${nativeType} for Xrays.");
              MOZ_ASSERT(!clasp->mNativeHooks->mIndexedOrNamedNativeProperties ||
                         !clasp->mNativeHooks->mIndexedOrNamedNativeProperties->mEnumerateOwnProperties,
                         "Shouldn't enumerate the properties of the named properties object for ${nativeType} for Xrays.");
            }
            return namedPropertiesObject.get();
            """,
            getParentProto=getParentProto,
            ifaceName=self.descriptor.name,
            parentProto=parentProto,
            nativeType=self.descriptor.nativeType,
        )


def getRawConditionList(idlobj, cxName, objName, ignoreSecureContext=False):
    """
    Get the list of conditions for idlobj (to be used in "is this enabled"
    checks).  This will be returned as a CGList with " &&\n" as the separator,
    for readability.

    objName is the name of the object that we're working with, because some of
    our test functions want that.

    ignoreSecureContext is used only for constructors in which the WebIDL interface
    itself is already marked as [SecureContext]. There is no need to do the work twice.
    """
    conditions = []
    pref = idlobj.getExtendedAttribute("Pref")
    if pref:
        assert isinstance(pref, list) and len(pref) == 1
        conditions.append("StaticPrefs::%s()" % prefIdentifier(pref[0]))
    if isChromeOnly(idlobj):
        conditions.append("nsContentUtils::ThreadsafeIsSystemCaller(%s)" % cxName)
    func = idlobj.getExtendedAttribute("Func")
    if func:
        assert isinstance(func, list) and len(func) == 1
        conditions.append("%s(%s, %s)" % (func[0], cxName, objName))
    trial = idlobj.getExtendedAttribute("Trial")
    if trial:
        assert isinstance(trial, list) and len(trial) == 1
        conditions.append(
            "OriginTrials::IsEnabled(%s, %s, OriginTrial::%s)"
            % (cxName, objName, trial[0])
        )
    if not ignoreSecureContext and idlobj.getExtendedAttribute("SecureContext"):
        conditions.append(
            "mozilla::dom::IsSecureContextOrObjectIsFromSecureContext(%s, %s)"
            % (cxName, objName)
        )
    return conditions


def getConditionList(idlobj, cxName, objName, ignoreSecureContext=False):
    """
    Get the list of conditions from getRawConditionList
    See comment on getRawConditionList above for more info about arguments.

    The return value is a possibly-empty conjunctive CGList of conditions.
    """
    conditions = getRawConditionList(idlobj, cxName, objName, ignoreSecureContext)
    return CGList((CGGeneric(cond) for cond in conditions), " &&\n")


class CGConstructorEnabled(CGAbstractMethod):
    """
    A method for testing whether we should be exposing this interface object.
    This can perform various tests depending on what conditions are specified
    on the interface.
    """

    def __init__(self, descriptor):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "ConstructorEnabled",
            "bool",
            [Argument("JSContext*", "aCx"), Argument("JS::Handle<JSObject*>", "aObj")],
        )

    def definition_body(self):
        body = CGList([], "\n")

        iface = self.descriptor.interface

        if not iface.isExposedInWindow():
            exposedInWindowCheck = dedent(
                """
                MOZ_ASSERT(!NS_IsMainThread(), "Why did we even get called?");
                """
            )
            body.append(CGGeneric(exposedInWindowCheck))

        if iface.isExposedInSomeButNotAllWorkers():
            workerGlobals = sorted(iface.getWorkerExposureSet())
            workerCondition = CGList(
                (
                    CGGeneric('strcmp(name, "%s")' % workerGlobal)
                    for workerGlobal in workerGlobals
                ),
                " && ",
            )
            exposedInWorkerCheck = fill(
                """
                const char* name = JS::GetClass(aObj)->name;
                if (${workerCondition}) {
                  return false;
                }
                """,
                workerCondition=workerCondition.define(),
            )
            exposedInWorkerCheck = CGGeneric(exposedInWorkerCheck)
            if iface.isExposedInWindow():
                exposedInWorkerCheck = CGIfWrapper(
                    exposedInWorkerCheck, "!NS_IsMainThread()"
                )
            body.append(exposedInWorkerCheck)

        conditions = getConditionList(iface, "aCx", "aObj")

        # We should really have some conditions
        assert len(body) or len(conditions)

        conditionsWrapper = ""
        if len(conditions):
            conditionsWrapper = CGWrapper(
                conditions, pre="return ", post=";\n", reindent=True
            )
        else:
            conditionsWrapper = CGGeneric("return true;\n")

        body.append(conditionsWrapper)
        return body.define()


def StructuredCloneTag(name):
    return "SCTAG_DOM_%s" % name.upper()


class CGSerializer(CGAbstractStaticMethod):
    """
    Implementation of serialization for things marked [Serializable].
    This gets stored in our DOMJSClass, so it can be static.

    The caller is expected to pass in the object whose DOMJSClass it
    used to get the serializer.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("JSStructuredCloneWriter*", "aWriter"),
            Argument("JS::Handle<JSObject*>", "aObj"),
        ]
        CGAbstractStaticMethod.__init__(self, descriptor, "Serialize", "bool", args)

    def definition_body(self):
        return fill(
            """
            MOZ_ASSERT(IsDOMObject(aObj), "Non-DOM object passed");
            MOZ_ASSERT(GetDOMClass(aObj)->mSerializer == &Serialize,
                       "Wrong object passed");
            return JS_WriteUint32Pair(aWriter, ${tag}, 0) &&
                   UnwrapDOMObject<${type}>(aObj)->WriteStructuredClone(aCx, aWriter);
            """,
            tag=StructuredCloneTag(self.descriptor.name),
            type=self.descriptor.nativeType,
        )


class CGDeserializer(CGAbstractMethod):
    """
    Implementation of deserialization for things marked [Serializable].
    This will need to be accessed from WebIDLSerializable, so can't be static.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("nsIGlobalObject*", "aGlobal"),
            Argument("JSStructuredCloneReader*", "aReader"),
        ]
        CGAbstractMethod.__init__(self, descriptor, "Deserialize", "JSObject*", args)

    def definition_body(self):
        # WrapObject has different signatures depending on whether
        # the object is wrappercached.
        if self.descriptor.wrapperCache:
            wrapCall = dedent(
                """
                result = obj->WrapObject(aCx, nullptr);
                if (!result) {
                  return nullptr;
                }
                """
            )
        else:
            wrapCall = dedent(
                """
                if (!obj->WrapObject(aCx, nullptr, &result)) {
                  return nullptr;
                }
                """
            )

        return fill(
            """
            // Protect the result from a moving GC in ~RefPtr
            JS::Rooted<JSObject*> result(aCx);
            {  // Scope for the RefPtr
              RefPtr<${type}> obj = ${type}::ReadStructuredClone(aCx, aGlobal, aReader);
              if (!obj) {
                return nullptr;
              }
              $*{wrapCall}
            }
            return result;
            """,
            type=self.descriptor.nativeType,
            wrapCall=wrapCall,
        )


def CreateBindingJSObject(descriptor):
    objDecl = "BindingJSObjectCreator<%s> creator(aCx);\n" % descriptor.nativeType

    # We don't always need to root obj, but there are a variety
    # of cases where we do, so for simplicity, just always root it.
    if descriptor.proxy:
        if descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns"):
            assert not descriptor.isMaybeCrossOriginObject()
            create = dedent(
                """
                aObject->mExpandoAndGeneration.expando.setUndefined();
                JS::Rooted<JS::Value> expandoValue(aCx, JS::PrivateValue(&aObject->mExpandoAndGeneration));
                creator.CreateProxyObject(aCx, &sClass.mBase, DOMProxyHandler::getInstance(),
                                          proto, /* aLazyProto = */ false, aObject,
                                          expandoValue, aReflector);
                """
            )
        else:
            if descriptor.isMaybeCrossOriginObject():
                proto = "nullptr"
                lazyProto = "true"
            else:
                proto = "proto"
                lazyProto = "false"
            create = fill(
                """
                creator.CreateProxyObject(aCx, &sClass.mBase, DOMProxyHandler::getInstance(),
                                          ${proto}, /* aLazyProto = */ ${lazyProto},
                                          aObject, JS::UndefinedHandleValue, aReflector);
                """,
                proto=proto,
                lazyProto=lazyProto,
            )
    else:
        create = dedent(
            """
            creator.CreateObject(aCx, sClass.ToJSClass(), proto, aObject, aReflector);
            """
        )
    return (
        objDecl
        + create
        + dedent(
            """
        if (!aReflector) {
          return false;
        }
        """
        )
    )


def InitUnforgeablePropertiesOnHolder(
    descriptor, properties, failureCode, holderName="unforgeableHolder"
):
    """
    Define the unforgeable properties on the unforgeable holder for
    the interface represented by descriptor.

    properties is a PropertyArrays instance.

    """
    assert (
        properties.unforgeableAttrs.hasNonChromeOnly()
        or properties.unforgeableAttrs.hasChromeOnly()
        or properties.unforgeableMethods.hasNonChromeOnly()
        or properties.unforgeableMethods.hasChromeOnly()
    )

    unforgeables = []

    defineUnforgeableAttrs = fill(
        """
        if (!DefineLegacyUnforgeableAttributes(aCx, ${holderName}, %s)) {
          $*{failureCode}
        }
        """,
        failureCode=failureCode,
        holderName=holderName,
    )
    defineUnforgeableMethods = fill(
        """
        if (!DefineLegacyUnforgeableMethods(aCx, ${holderName}, %s)) {
          $*{failureCode}
        }
        """,
        failureCode=failureCode,
        holderName=holderName,
    )

    unforgeableMembers = [
        (defineUnforgeableAttrs, properties.unforgeableAttrs),
        (defineUnforgeableMethods, properties.unforgeableMethods),
    ]
    for template, array in unforgeableMembers:
        if array.hasNonChromeOnly():
            unforgeables.append(CGGeneric(template % array.variableName(False)))
        if array.hasChromeOnly():
            unforgeables.append(
                CGIfWrapper(
                    CGGeneric(template % array.variableName(True)),
                    "nsContentUtils::ThreadsafeIsSystemCaller(aCx)",
                )
            )

    if descriptor.interface.getExtendedAttribute("LegacyUnforgeable"):
        # We do our undefined toPrimitive here, not as a regular property
        # because we don't have a concept of value props anywhere in IDL.
        unforgeables.append(
            CGGeneric(
                fill(
                    """
            JS::Rooted<JS::PropertyKey> toPrimitive(aCx,
              JS::GetWellKnownSymbolKey(aCx, JS::SymbolCode::toPrimitive));
            if (!JS_DefinePropertyById(aCx, ${holderName}, toPrimitive,
                                       JS::UndefinedHandleValue,
                                       JSPROP_READONLY | JSPROP_PERMANENT)) {
              $*{failureCode}
            }
            """,
                    failureCode=failureCode,
                    holderName=holderName,
                )
            )
        )

    return CGWrapper(CGList(unforgeables), pre="\n")


def CopyUnforgeablePropertiesToInstance(descriptor, failureCode):
    """
    Copy the unforgeable properties from the unforgeable holder for
    this interface to the instance object we have.
    """
    assert not descriptor.isGlobal()

    if not descriptor.hasLegacyUnforgeableMembers:
        return ""

    copyCode = [
        CGGeneric(
            dedent(
                """
            // Important: do unforgeable property setup after we have handed
            // over ownership of the C++ object to obj as needed, so that if
            // we fail and it ends up GCed it won't have problems in the
            // finalizer trying to drop its ownership of the C++ object.
            """
            )
        )
    ]

    # For proxies, we want to define on the expando object, not directly on the
    # reflector, so we can make sure we don't get confused by named getters.
    if descriptor.proxy:
        copyCode.append(
            CGGeneric(
                fill(
                    """
            JS::Rooted<JSObject*> expando(aCx,
              DOMProxyHandler::EnsureExpandoObject(aCx, aReflector));
            if (!expando) {
              $*{failureCode}
            }
            """,
                    failureCode=failureCode,
                )
            )
        )
        obj = "expando"
    else:
        obj = "aReflector"

    copyCode.append(
        CGGeneric(
            fill(
                """
        JS::Rooted<JSObject*> unforgeableHolder(aCx,
          &JS::GetReservedSlot(canonicalProto, DOM_INTERFACE_PROTO_SLOTS_BASE).toObject());
        if (!JS_InitializePropertiesFromCompatibleNativeObject(aCx, ${obj}, unforgeableHolder)) {
          $*{failureCode}
        }
        """,
                obj=obj,
                failureCode=failureCode,
            )
        )
    )

    return CGWrapper(CGList(copyCode), pre="\n").define()


def AssertInheritanceChain(descriptor):
    # We can skip the reinterpret_cast check for the descriptor's nativeType
    # if aObject is a pointer of that type.
    asserts = fill(
        """
        static_assert(std::is_same_v<decltype(aObject), ${nativeType}*>);
        """,
        nativeType=descriptor.nativeType,
    )
    iface = descriptor.interface
    while iface.parent:
        iface = iface.parent
        desc = descriptor.getDescriptor(iface.identifier.name)
        asserts += (
            "MOZ_ASSERT(static_cast<%s*>(aObject) == \n"
            "           reinterpret_cast<%s*>(aObject),\n"
            '           "Multiple inheritance for %s is broken.");\n'
            % (desc.nativeType, desc.nativeType, desc.nativeType)
        )
    asserts += "MOZ_ASSERT(ToSupportsIsCorrect(aObject));\n"
    return asserts


def InitMemberSlots(descriptor, failureCode):
    """
    Initialize member slots on our JS object if we're supposed to have some.

    Note that this is called after the SetWrapper() call in the
    wrapperCache case, since that can affect how our getters behave
    and we plan to invoke them here.  So if we fail, we need to
    ClearWrapper.
    """
    if not descriptor.interface.hasMembersInSlots():
        return ""
    return fill(
        """
        if (!UpdateMemberSlots(aCx, aReflector, aObject)) {
          $*{failureCode}
        }
        """,
        failureCode=failureCode,
    )


def DeclareProto(descriptor, noGivenProto=False):
    """
    Declare the canonicalProto and proto we have for our wrapping operation.
    """
    getCanonical = dedent(
        """
        JS::Handle<JSObject*> ${canonicalProto} = GetProtoObjectHandle(aCx);
        if (!${canonicalProto}) {
          return false;
        }
        """
    )

    if noGivenProto:
        return fill(getCanonical, canonicalProto="proto")

    getCanonical = fill(getCanonical, canonicalProto="canonicalProto")

    preamble = getCanonical + dedent(
        """
        JS::Rooted<JSObject*> proto(aCx);
        """
    )
    if descriptor.isMaybeCrossOriginObject():
        return preamble + dedent(
            """
            MOZ_ASSERT(!aGivenProto,
                       "Shouldn't have constructors on cross-origin objects");
            // Set proto to canonicalProto to avoid preserving our wrapper if
            // we don't have to.
            proto = canonicalProto;
            """
        )

    return preamble + dedent(
        """
        if (aGivenProto) {
          proto = aGivenProto;
          // Unfortunately, while aGivenProto was in the compartment of aCx
          // coming in, we changed compartments to that of "parent" so may need
          // to wrap the proto here.
          if (js::GetContextCompartment(aCx) != JS::GetCompartment(proto)) {
            if (!JS_WrapObject(aCx, &proto)) {
              return false;
            }
          }
        } else {
          proto = canonicalProto;
        }
        """
    )


class CGWrapWithCacheMethod(CGAbstractMethod):
    """
    Create a wrapper JSObject for a given native that implements nsWrapperCache.
    """

    def __init__(self, descriptor):
        assert descriptor.interface.hasInterfacePrototypeObject()
        args = [
            Argument("JSContext*", "aCx"),
            Argument(descriptor.nativeType + "*", "aObject"),
            Argument("nsWrapperCache*", "aCache"),
            Argument("JS::Handle<JSObject*>", "aGivenProto"),
            Argument("JS::MutableHandle<JSObject*>", "aReflector"),
        ]
        CGAbstractMethod.__init__(self, descriptor, "Wrap", "bool", args)

    def definition_body(self):
        failureCode = dedent(
            """
            aCache->ReleaseWrapper(aObject);
            aCache->ClearWrapper();
            return false;
            """
        )

        if self.descriptor.proxy:
            finalize = "DOMProxyHandler::getInstance()->finalize"
        else:
            finalize = FINALIZE_HOOK_NAME

        return fill(
            """
            static_assert(!std::is_base_of_v<NonRefcountedDOMObject, ${nativeType}>,
                          "Shouldn't have wrappercached things that are not refcounted.");
            $*{assertInheritance}
            MOZ_ASSERT_IF(aGivenProto, js::IsObjectInContextCompartment(aGivenProto, aCx));
            MOZ_ASSERT(!aCache->GetWrapper(),
                       "You should probably not be using Wrap() directly; use "
                       "GetOrCreateDOMReflector instead");

            MOZ_ASSERT(ToSupportsIsOnPrimaryInheritanceChain(aObject, aCache),
                       "nsISupports must be on our primary inheritance chain");

            // If the wrapper cache contains a dead reflector then finalize that
            // now, ensuring that the finalizer for the old reflector always
            // runs before the new reflector is created and attached. This
            // avoids the awkward situation where there are multiple reflector
            // objects that contain pointers to the same native.

            if (JSObject* oldReflector = aCache->GetWrapperMaybeDead()) {
              ${finalize}(nullptr /* unused */, oldReflector);
              MOZ_ASSERT(!aCache->GetWrapperMaybeDead());
            }

            JS::Rooted<JSObject*> global(aCx, FindAssociatedGlobal(aCx, aObject->GetParentObject()));
            if (!global) {
              return false;
            }
            MOZ_ASSERT(JS_IsGlobalObject(global));
            JS::AssertObjectIsNotGray(global);

            // That might have ended up wrapping us already, due to the wonders
            // of XBL.  Check for that, and bail out as needed.
            aReflector.set(aCache->GetWrapper());
            if (aReflector) {
            #ifdef DEBUG
              AssertReflectorHasGivenProto(aCx, aReflector, aGivenProto);
            #endif // DEBUG
              return true;
            }

            JSAutoRealm ar(aCx, global);
            $*{declareProto}

            $*{createObject}

            aCache->SetWrapper(aReflector);
            $*{unforgeable}
            $*{slots}
            creator.InitializationSucceeded();

            MOZ_ASSERT(aCache->GetWrapperPreserveColor() &&
                       aCache->GetWrapperPreserveColor() == aReflector);
            // If proto != canonicalProto, we have to preserve our wrapper;
            // otherwise we won't be able to properly recreate it later, since
            // we won't know what proto to use.  Note that we don't check
            // aGivenProto here, since it's entirely possible (and even
            // somewhat common) to have a non-null aGivenProto which is the
            // same as canonicalProto.
            if (proto != canonicalProto) {
              PreserveWrapper(aObject);
            }

            return true;
            """,
            nativeType=self.descriptor.nativeType,
            assertInheritance=AssertInheritanceChain(self.descriptor),
            declareProto=DeclareProto(self.descriptor),
            createObject=CreateBindingJSObject(self.descriptor),
            unforgeable=CopyUnforgeablePropertiesToInstance(
                self.descriptor, failureCode
            ),
            slots=InitMemberSlots(self.descriptor, failureCode),
            finalize=finalize,
        )


class CGWrapMethod(CGAbstractMethod):
    def __init__(self, descriptor):
        # XXX can we wrap if we don't have an interface prototype object?
        assert descriptor.interface.hasInterfacePrototypeObject()
        args = [
            Argument("JSContext*", "aCx"),
            Argument("T*", "aObject"),
            Argument("JS::Handle<JSObject*>", "aGivenProto"),
        ]
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "Wrap",
            "JSObject*",
            args,
            inline=True,
            templateArgs=["class T"],
        )

    def definition_body(self):
        return dedent(
            """
            JS::Rooted<JSObject*> reflector(aCx);
            return Wrap(aCx, aObject, aObject, aGivenProto, &reflector) ? reflector.get() : nullptr;
            """
        )


class CGWrapNonWrapperCacheMethod(CGAbstractMethod):
    """
    Create a wrapper JSObject for a given native that does not implement
    nsWrapperCache.
    """

    def __init__(self, descriptor, static=False, signatureOnly=False):
        # XXX can we wrap if we don't have an interface prototype object?
        assert descriptor.interface.hasInterfacePrototypeObject()
        self.noGivenProto = (
            descriptor.interface.isIteratorInterface()
            or descriptor.interface.isAsyncIteratorInterface()
        )
        args = [
            Argument("JSContext*", "aCx"),
            Argument(descriptor.nativeType + "*", "aObject"),
        ]
        if not self.noGivenProto:
            args.append(Argument("JS::Handle<JSObject*>", "aGivenProto"))
        args.append(Argument("JS::MutableHandle<JSObject*>", "aReflector"))
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "Wrap",
            "bool",
            args,
            static=static,
            signatureOnly=signatureOnly,
        )

    def definition_body(self):
        failureCode = "return false;\n"

        declareProto = DeclareProto(self.descriptor, noGivenProto=self.noGivenProto)
        if self.noGivenProto:
            assertGivenProto = ""
        else:
            assertGivenProto = dedent(
                """
                MOZ_ASSERT_IF(aGivenProto, js::IsObjectInContextCompartment(aGivenProto, aCx));
                """
            )
        return fill(
            """
            $*{assertions}
            $*{assertGivenProto}

            JS::Rooted<JSObject*> global(aCx, JS::CurrentGlobalOrNull(aCx));
            $*{declareProto}

            $*{createObject}

            $*{unforgeable}

            $*{slots}

            creator.InitializationSucceeded();
            return true;
            """,
            assertions=AssertInheritanceChain(self.descriptor),
            assertGivenProto=assertGivenProto,
            declareProto=declareProto,
            createObject=CreateBindingJSObject(self.descriptor),
            unforgeable=CopyUnforgeablePropertiesToInstance(
                self.descriptor, failureCode
            ),
            slots=InitMemberSlots(self.descriptor, failureCode),
        )


class CGWrapGlobalMethod(CGAbstractMethod):
    """
    Create a wrapper JSObject for a global.  The global must implement
    nsWrapperCache.

    properties should be a PropertyArrays instance.
    """

    def __init__(self, descriptor, properties):
        assert (
            descriptor.interface.hasInterfacePrototypeObject()
            or descriptor.hasOrdinaryObjectPrototype()
        )
        args = [
            Argument("JSContext*", "aCx"),
            Argument(descriptor.nativeType + "*", "aObject"),
            Argument("nsWrapperCache*", "aCache"),
            Argument("JS::RealmOptions&", "aOptions"),
            Argument("JSPrincipals*", "aPrincipal"),
            Argument("JS::MutableHandle<JSObject*>", "aReflector"),
        ]
        CGAbstractMethod.__init__(self, descriptor, "Wrap", "bool", args)
        self.descriptor = descriptor
        self.properties = properties

    def definition_body(self):
        if self.properties.hasNonChromeOnly():
            properties = "sNativeProperties.Upcast()"
        else:
            properties = "nullptr"
        if self.properties.hasChromeOnly():
            chromeProperties = "nsContentUtils::ThreadsafeIsSystemCaller(aCx) ? sChromeOnlyNativeProperties.Upcast() : nullptr"
        else:
            chromeProperties = "nullptr"

        failureCode = dedent(
            """
            aCache->ReleaseWrapper(aObject);
            aCache->ClearWrapper();
            return false;
            """
        )

        if self.descriptor.hasLegacyUnforgeableMembers:
            unforgeable = InitUnforgeablePropertiesOnHolder(
                self.descriptor, self.properties, failureCode, "aReflector"
            ).define()
        else:
            unforgeable = ""

        if self.descriptor.hasOrdinaryObjectPrototype():
            getProto = "JS::GetRealmObjectPrototypeHandle"
        else:
            getProto = "GetProtoObjectHandle"
        return fill(
            """
            $*{assertions}
            MOZ_ASSERT(ToSupportsIsOnPrimaryInheritanceChain(aObject, aCache),
                       "nsISupports must be on our primary inheritance chain");

            if (!CreateGlobal<${nativeType}, ${getProto}>(aCx,
                                             aObject,
                                             aCache,
                                             sClass.ToJSClass(),
                                             aOptions,
                                             aPrincipal,
                                             aReflector)) {
              $*{failureCode}
            }

            // aReflector is a new global, so has a new realm.  Enter it
            // before doing anything with it.
            JSAutoRealm ar(aCx, aReflector);

            if (!DefineProperties(aCx, aReflector, ${properties}, ${chromeProperties})) {
              $*{failureCode}
            }
            $*{unforgeable}

            $*{slots}

            return true;
            """,
            assertions=AssertInheritanceChain(self.descriptor),
            nativeType=self.descriptor.nativeType,
            getProto=getProto,
            properties=properties,
            chromeProperties=chromeProperties,
            failureCode=failureCode,
            unforgeable=unforgeable,
            slots=InitMemberSlots(self.descriptor, failureCode),
        )


class CGUpdateMemberSlotsMethod(CGAbstractStaticMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("JS::Handle<JSObject*>", "aWrapper"),
            Argument(descriptor.nativeType + "*", "aObject"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, "UpdateMemberSlots", "bool", args
        )

    def definition_body(self):
        body = "JS::Rooted<JS::Value> temp(aCx);\n" "JSJitGetterCallArgs args(&temp);\n"
        for m in self.descriptor.interface.members:
            if m.isAttr() and m.getExtendedAttribute("StoreInSlot"):
                # Skip doing this for the "window" and "self" attributes on the
                # Window interface, because those can't be gotten safely until
                # we have hooked it up correctly to the outer window.  The
                # window code handles doing the get itself.
                if self.descriptor.interface.identifier.name == "Window" and (
                    m.identifier.name == "window" or m.identifier.name == "self"
                ):
                    continue
                body += fill(
                    """

                    static_assert(${slot} < JS::shadow::Object::MAX_FIXED_SLOTS,
                                  "Not enough fixed slots to fit '${interface}.${member}.  Ion's visitGetDOMMemberV/visitGetDOMMemberT assume StoreInSlot things are all in fixed slots.");
                    if (!get_${member}(aCx, aWrapper, aObject, args)) {
                      return false;
                    }
                    // Getter handled setting our reserved slots
                    """,
                    slot=memberReservedSlot(m, self.descriptor),
                    interface=self.descriptor.interface.identifier.name,
                    member=m.identifier.name,
                )

        body += "\nreturn true;\n"
        return body


class CGClearCachedValueMethod(CGAbstractMethod):
    def __init__(self, descriptor, member):
        self.member = member
        # If we're StoreInSlot, we'll need to call the getter
        if member.getExtendedAttribute("StoreInSlot"):
            args = [Argument("JSContext*", "aCx")]
            returnType = "bool"
        else:
            args = []
            returnType = "void"
        args.append(Argument(descriptor.nativeType + "*", "aObject"))
        name = MakeClearCachedValueNativeName(member)
        CGAbstractMethod.__init__(self, descriptor, name, returnType, args)

    def definition_body(self):
        slotIndex = memberReservedSlot(self.member, self.descriptor)
        clearCachedValue = fill(
            """
            JS::SetReservedSlot(obj, ${slotIndex}, JS::UndefinedValue());
            """,
            slotIndex=slotIndex,
        )
        if self.member.getExtendedAttribute("StoreInSlot"):
            # We have to root things and save the old value in case
            # regetting fails, so we can restore it.
            declObj = "JS::Rooted<JSObject*> obj(aCx);\n"
            noopRetval = " true"
            saveMember = (
                "JS::Rooted<JS::Value> oldValue(aCx, JS::GetReservedSlot(obj, %s));\n"
                % slotIndex
            )
            regetMember = fill(
                """
                JS::Rooted<JS::Value> temp(aCx);
                JSJitGetterCallArgs args(&temp);
                JSAutoRealm ar(aCx, obj);
                if (!get_${name}(aCx, obj, aObject, args)) {
                  JS::SetReservedSlot(obj, ${slotIndex}, oldValue);
                  return false;
                }
                return true;
                """,
                name=self.member.identifier.name,
                slotIndex=slotIndex,
            )
        else:
            declObj = "JSObject* obj;\n"
            noopRetval = ""
            saveMember = ""
            if self.member.getExtendedAttribute(
                "ReflectedHTMLAttributeReturningFrozenArray"
            ):
                clearCachedValue = fill(
                    """
                    ReflectedHTMLAttributeSlots::Clear(obj, ${arrayIndex});
                    """,
                    arrayIndex=reflectedHTMLAttributesArrayIndex(
                        self.descriptor, self.member
                    ),
                )
            regetMember = ""

        if self.descriptor.wantsXrays:
            if self.member.getExtendedAttribute("StoreInSlot"):
                cx = "JS::RootingContext::get(aCx)"
            else:
                cx = "RootingCx()"
            if self.member.getExtendedAttribute(
                "ReflectedHTMLAttributeReturningFrozenArray"
            ):
                clearXrayExpandoSlots = fill(
                    """
                    ReflectedHTMLAttributeSlots::ClearInXrays(${cx}, obj, ${arrayIndex});
                    """,
                    cx=cx,
                    arrayIndex=reflectedHTMLAttributesArrayIndex(
                        self.descriptor, self.member
                    ),
                )
            else:
                clearXrayExpandoSlots = fill(
                    """
                    ClearXrayExpandoSlots(${cx}, obj, ${xraySlotIndex});
                    """,
                    cx=cx,
                    xraySlotIndex=memberXrayExpandoReservedSlot(
                        self.member, self.descriptor
                    ),
                )
        else:
            clearXrayExpandoSlots = ""

        return fill(
            """
            $*{declObj}
            obj = aObject->GetWrapper();
            if (!obj) {
              return${noopRetval};
            }
            $*{saveMember}
            $*{clearCachedValue}
            $*{clearXrayExpandoSlots}
            $*{regetMember}
            """,
            declObj=declObj,
            noopRetval=noopRetval,
            saveMember=saveMember,
            slotIndex=slotIndex,
            clearCachedValue=clearCachedValue,
            clearXrayExpandoSlots=clearXrayExpandoSlots,
            regetMember=regetMember,
        )


class CGCrossOriginProperties(CGThing):
    def __init__(self, descriptor):
        attrs = []
        chromeOnlyAttrs = []
        methods = []
        chromeOnlyMethods = []
        for m in descriptor.interface.members:
            if m.isAttr() and (
                m.getExtendedAttribute("CrossOriginReadable")
                or m.getExtendedAttribute("CrossOriginWritable")
            ):
                if m.isStatic():
                    raise TypeError(
                        "Don't know how to deal with static method %s"
                        % m.identifier.name
                    )
                if PropertyDefiner.getControllingCondition(
                    m, descriptor
                ).hasDisablers():
                    raise TypeError(
                        "Don't know how to deal with disabler for %s"
                        % m.identifier.name
                    )
                if len(m.bindingAliases) > 0:
                    raise TypeError(
                        "Don't know how to deal with aliases for %s" % m.identifier.name
                    )
                if m.getExtendedAttribute("ChromeOnly") is not None:
                    chromeOnlyAttrs.extend(AttrDefiner.attrData(m, overrideFlags="0"))
                else:
                    attrs.extend(AttrDefiner.attrData(m, overrideFlags="0"))
            elif m.isMethod() and m.getExtendedAttribute("CrossOriginCallable"):
                if m.isStatic():
                    raise TypeError(
                        "Don't know how to deal with static method %s"
                        % m.identifier.name
                    )
                if PropertyDefiner.getControllingCondition(
                    m, descriptor
                ).hasDisablers():
                    raise TypeError(
                        "Don't know how to deal with disabler for %s"
                        % m.identifier.name
                    )
                if len(m.aliases) > 0:
                    raise TypeError(
                        "Don't know how to deal with aliases for %s" % m.identifier.name
                    )
                if m.getExtendedAttribute("ChromeOnly") is not None:
                    chromeOnlyMethods.append(
                        MethodDefiner.methodData(
                            m, descriptor, overrideFlags="JSPROP_READONLY"
                        )
                    )
                else:
                    methods.append(
                        MethodDefiner.methodData(
                            m, descriptor, overrideFlags="JSPROP_READONLY"
                        )
                    )

        if len(attrs) > 0:
            self.attributeSpecs, _ = PropertyDefiner.generatePrefableArrayValues(
                attrs,
                descriptor,
                AttrDefiner.formatSpec,
                "  JS_PS_END\n",
                AttrDefiner.condition,
                functools.partial(AttrDefiner.specData, crossOriginOnly=True),
            )
        else:
            self.attributeSpecs = [" JS_PS_END\n"]
        if len(methods) > 0:
            self.methodSpecs, _ = PropertyDefiner.generatePrefableArrayValues(
                methods,
                descriptor,
                MethodDefiner.formatSpec,
                "  JS_FS_END\n",
                MethodDefiner.condition,
                MethodDefiner.specData,
            )
        else:
            self.methodSpecs = ["  JS_FS_END\n"]

        if len(chromeOnlyAttrs) > 0:
            (
                self.chromeOnlyAttributeSpecs,
                _,
            ) = PropertyDefiner.generatePrefableArrayValues(
                chromeOnlyAttrs,
                descriptor,
                AttrDefiner.formatSpec,
                "  JS_PS_END\n",
                AttrDefiner.condition,
                functools.partial(AttrDefiner.specData, crossOriginOnly=True),
            )
        else:
            self.chromeOnlyAttributeSpecs = []
        if len(chromeOnlyMethods) > 0:
            self.chromeOnlyMethodSpecs, _ = PropertyDefiner.generatePrefableArrayValues(
                chromeOnlyMethods,
                descriptor,
                MethodDefiner.formatSpec,
                "  JS_FS_END\n",
                MethodDefiner.condition,
                MethodDefiner.specData,
            )
        else:
            self.chromeOnlyMethodSpecs = []

    def declare(self):
        return dedent(
            """
            extern const CrossOriginProperties sCrossOriginProperties;
            """
        )

    def define(self):
        def defineChromeOnly(name, specs, specType):
            if len(specs) == 0:
                return ("", "nullptr")
            name = "sChromeOnlyCrossOrigin" + name
            define = fill(
                """
                static const ${specType} ${name}[] = {
                  $*{specs}
                };
                """,
                specType=specType,
                name=name,
                specs=",\n".join(specs),
            )
            return (define, name)

        chromeOnlyAttributes = defineChromeOnly(
            "Attributes", self.chromeOnlyAttributeSpecs, "JSPropertySpec"
        )
        chromeOnlyMethods = defineChromeOnly(
            "Methods", self.chromeOnlyMethodSpecs, "JSFunctionSpec"
        )
        return fill(
            """
            static const JSPropertySpec sCrossOriginAttributes[] = {
              $*{attributeSpecs}
            };
            static const JSFunctionSpec sCrossOriginMethods[] = {
              $*{methodSpecs}
            };
            $*{chromeOnlyAttributeSpecs}
            $*{chromeOnlyMethodSpecs}
            const CrossOriginProperties sCrossOriginProperties = {
              sCrossOriginAttributes,
              sCrossOriginMethods,
              ${chromeOnlyAttributes},
              ${chromeOnlyMethods}
            };
            """,
            attributeSpecs=",\n".join(self.attributeSpecs),
            methodSpecs=",\n".join(self.methodSpecs),
            chromeOnlyAttributeSpecs=chromeOnlyAttributes[0],
            chromeOnlyMethodSpecs=chromeOnlyMethods[0],
            chromeOnlyAttributes=chromeOnlyAttributes[1],
            chromeOnlyMethods=chromeOnlyMethods[1],
        )


class CGCycleCollectionTraverseForOwningUnionMethod(CGAbstractMethod):
    """
    ImplCycleCollectionUnlink for owning union type.
    """

    def __init__(self, type):
        self.type = type
        args = [
            Argument("nsCycleCollectionTraversalCallback&", "aCallback"),
            Argument("%s&" % CGUnionStruct.unionTypeName(type, True), "aUnion"),
            Argument("const char*", "aName"),
            Argument("uint32_t", "aFlags", "0"),
        ]
        CGAbstractMethod.__init__(
            self, None, "ImplCycleCollectionTraverse", "void", args
        )

    def deps(self):
        return self.type.getDeps()

    def definition_body(self):
        memberNames = [
            getUnionMemberName(t)
            for t in self.type.flatMemberTypes
            if idlTypeNeedsCycleCollection(t)
        ]
        assert memberNames

        conditionTemplate = "aUnion.Is%s()"
        functionCallTemplate = (
            'ImplCycleCollectionTraverse(aCallback, aUnion.GetAs%s(), "m%s", aFlags);\n'
        )

        ifStaments = (
            CGIfWrapper(CGGeneric(functionCallTemplate % (m, m)), conditionTemplate % m)
            for m in memberNames
        )

        return CGElseChain(ifStaments).define()


class CGCycleCollectionUnlinkForOwningUnionMethod(CGAbstractMethod):
    """
    ImplCycleCollectionUnlink for owning union type.
    """

    def __init__(self, type):
        self.type = type
        args = [Argument("%s&" % CGUnionStruct.unionTypeName(type, True), "aUnion")]
        CGAbstractMethod.__init__(self, None, "ImplCycleCollectionUnlink", "void", args)

    def deps(self):
        return self.type.getDeps()

    def definition_body(self):
        return "aUnion.Uninit();\n"


builtinNames = {
    IDLType.Tags.bool: "bool",
    IDLType.Tags.int8: "int8_t",
    IDLType.Tags.int16: "int16_t",
    IDLType.Tags.int32: "int32_t",
    IDLType.Tags.int64: "int64_t",
    IDLType.Tags.uint8: "uint8_t",
    IDLType.Tags.uint16: "uint16_t",
    IDLType.Tags.uint32: "uint32_t",
    IDLType.Tags.uint64: "uint64_t",
    IDLType.Tags.unrestricted_float: "float",
    IDLType.Tags.float: "float",
    IDLType.Tags.unrestricted_double: "double",
    IDLType.Tags.double: "double",
}

numericSuffixes = {
    IDLType.Tags.int8: "",
    IDLType.Tags.uint8: "",
    IDLType.Tags.int16: "",
    IDLType.Tags.uint16: "",
    IDLType.Tags.int32: "",
    IDLType.Tags.uint32: "U",
    IDLType.Tags.int64: "LL",
    IDLType.Tags.uint64: "ULL",
    IDLType.Tags.unrestricted_float: "F",
    IDLType.Tags.float: "F",
    IDLType.Tags.unrestricted_double: "",
    IDLType.Tags.double: "",
}


def numericValue(t, v):
    if t == IDLType.Tags.unrestricted_double or t == IDLType.Tags.unrestricted_float:
        typeName = builtinNames[t]
        if v == float("inf"):
            return "mozilla::PositiveInfinity<%s>()" % typeName
        if v == float("-inf"):
            return "mozilla::NegativeInfinity<%s>()" % typeName
        if math.isnan(v):
            return "mozilla::UnspecifiedNaN<%s>()" % typeName
    return "%s%s" % (v, numericSuffixes[t])


class CastableObjectUnwrapper:
    """
    A class for unwrapping an object stored in a JS Value (or
    MutableHandle<Value> or Handle<Value>) named by the "source" and
    "mutableSource" arguments based on the passed-in descriptor and storing it
    in a variable called by the name in the "target" argument.  The "source"
    argument should be able to produce a Value or Handle<Value>; the
    "mutableSource" argument should be able to produce a MutableHandle<Value>

    codeOnFailure is the code to run if unwrapping fails.

    If isCallbackReturnValue is "JSImpl" and our descriptor is also
    JS-implemented, fall back to just creating the right object if what we
    have isn't one already.
    """

    def __init__(
        self,
        descriptor,
        source,
        mutableSource,
        target,
        codeOnFailure,
        exceptionCode=None,
        isCallbackReturnValue=False,
    ):
        self.substitution = {
            "type": descriptor.nativeType,
            "protoID": "prototypes::id::" + descriptor.name,
            "target": target,
            "codeOnFailure": codeOnFailure,
            "source": source,
            "mutableSource": mutableSource,
        }

        if isCallbackReturnValue == "JSImpl" and descriptor.interface.isJSImplemented():
            exceptionCode = exceptionCode or codeOnFailure
            self.substitution["codeOnFailure"] = fill(
                """
                // Be careful to not wrap random DOM objects here, even if
                // they're wrapped in opaque security wrappers for some reason.
                // XXXbz Wish we could check for a JS-implemented object
                // that already has a content reflection...
                if (!IsDOMObject(js::UncheckedUnwrap(&${source}.toObject()))) {
                  nsCOMPtr<nsIGlobalObject> contentGlobal;
                  JS::Rooted<JSObject*> callback(cx, CallbackOrNull());
                  if (!callback ||
                      !GetContentGlobalForJSImplementedObject(cx, callback, getter_AddRefs(contentGlobal))) {
                    $*{exceptionCode}
                  }
                  JS::Rooted<JSObject*> jsImplSourceObj(cx, &${source}.toObject());
                  MOZ_RELEASE_ASSERT(!js::IsWrapper(jsImplSourceObj),
                                     "Don't return JS implementations from other compartments");
                  JS::Rooted<JSObject*> jsImplSourceGlobal(cx, JS::GetNonCCWObjectGlobal(jsImplSourceObj));
                  ${target} = new ${type}(jsImplSourceObj, jsImplSourceGlobal, contentGlobal);
                } else {
                  $*{codeOnFailure}
                }
                """,
                exceptionCode=exceptionCode,
                **self.substitution,
            )
        else:
            self.substitution["codeOnFailure"] = codeOnFailure

    def __str__(self):
        substitution = self.substitution.copy()
        substitution["codeOnFailure"] %= {
            "securityError": "rv == NS_ERROR_XPC_SECURITY_MANAGER_VETO"
        }
        return fill(
            """
            {
              // Our JSContext should be in the right global to do unwrapping in.
              nsresult rv = UnwrapObject<${protoID}, ${type}>(${mutableSource}, ${target}, cx);
              if (NS_FAILED(rv)) {
                $*{codeOnFailure}
              }
            }
            """,
            **substitution,
        )


class FailureFatalCastableObjectUnwrapper(CastableObjectUnwrapper):
    """
    As CastableObjectUnwrapper, but defaulting to throwing if unwrapping fails
    """

    def __init__(
        self,
        descriptor,
        source,
        mutableSource,
        target,
        exceptionCode,
        isCallbackReturnValue,
        sourceDescription,
    ):
        CastableObjectUnwrapper.__init__(
            self,
            descriptor,
            source,
            mutableSource,
            target,
            'cx.ThrowErrorMessage<MSG_DOES_NOT_IMPLEMENT_INTERFACE>("%s", "%s");\n'
            "%s"
            % (sourceDescription, descriptor.interface.identifier.name, exceptionCode),
            exceptionCode,
            isCallbackReturnValue,
        )


def getCallbackConversionInfo(
    type, idlObject, isMember, isCallbackReturnValue, isOptional
):
    """
    Returns a tuple containing the declType, declArgs, and basic
    conversion for the given callback type, with the given callback
    idl object in the given context (isMember/isCallbackReturnValue/isOptional).
    """
    name = idlObject.identifier.name

    # We can't use fast callbacks if isOptional because then we get an
    # Optional<RootedCallback> thing, which is not transparent to consumers.
    useFastCallback = (
        (not isMember or isMember == "Union")
        and not isCallbackReturnValue
        and not isOptional
    )
    if useFastCallback:
        name = "binding_detail::Fast%s" % name
        rootArgs = ""
        args = "&${val}.toObject(), JS::CurrentGlobalOrNull(cx)"
    else:
        rootArgs = dedent(
            """
            JS::Rooted<JSObject*> tempRoot(cx, &${val}.toObject());
            JS::Rooted<JSObject*> tempGlobalRoot(cx, JS::CurrentGlobalOrNull(cx));
            """
        )
        args = "cx, tempRoot, tempGlobalRoot, GetIncumbentGlobal()"

    if type.nullable() or isCallbackReturnValue:
        declType = CGGeneric("RefPtr<%s>" % name)
    else:
        declType = CGGeneric("OwningNonNull<%s>" % name)

    if useFastCallback:
        declType = CGTemplatedType("RootedCallback", declType)
        declArgs = "cx"
    else:
        declArgs = None

    conversion = fill(
        """
        { // scope for tempRoot and tempGlobalRoot if needed
          $*{rootArgs}
          $${declName} = new ${name}(${args});
        }
        """,
        rootArgs=rootArgs,
        name=name,
        args=args,
    )
    return (declType, declArgs, conversion)


class JSToNativeConversionInfo:
    """
    An object representing information about a JS-to-native conversion.
    """

    def __init__(
        self,
        template,
        declType=None,
        holderType=None,
        dealWithOptional=False,
        declArgs=None,
        holderArgs=None,
    ):
        """
        template: A string representing the conversion code.  This will have
                  template substitution performed on it as follows:

          ${val} is a handle to the JS::Value in question
          ${maybeMutableVal} May be a mutable handle to the JS::Value in
                             question. This is only OK to use if ${val} is
                             known to not be undefined.
          ${holderName} replaced by the holder's name, if any
          ${declName} replaced by the declaration's name
          ${haveValue} replaced by an expression that evaluates to a boolean
                       for whether we have a JS::Value.  Only used when
                       defaultValue is not None or when True is passed for
                       checkForValue to instantiateJSToNativeConversion.
                       This expression may not be already-parenthesized, so if
                       you use it with && or || make sure to put parens
                       around it.
          ${passedToJSImpl} replaced by an expression that evaluates to a boolean
                            for whether this value is being passed to a JS-
                            implemented interface.

        declType: A CGThing representing the native C++ type we're converting
                  to.  This is allowed to be None if the conversion code is
                  supposed to be used as-is.

        holderType: A CGThing representing the type of a "holder" which will
                    hold a possible reference to the C++ thing whose type we
                    returned in declType, or  None if no such holder is needed.

        dealWithOptional: A boolean indicating whether the caller has to do
                          optional-argument handling.  This should only be set
                          to true if the JS-to-native conversion is being done
                          for an optional argument or dictionary member with no
                          default value and if the returned template expects
                          both declType and holderType to be wrapped in
                          Optional<>, with ${declName} and ${holderName}
                          adjusted to point to the Value() of the Optional, and
                          Construct() calls to be made on the Optional<>s as
                          needed.

        declArgs: If not None, the arguments to pass to the ${declName}
                  constructor.  These will have template substitution performed
                  on them so you can use things like ${val}.  This is a
                  single string, not a list of strings.

        holderArgs: If not None, the arguments to pass to the ${holderName}
                    constructor.  These will have template substitution
                    performed on them so you can use things like ${val}.
                    This is a single string, not a list of strings.

        ${declName} must be in scope before the code from 'template' is entered.

        If holderType is not None then ${holderName} must be in scope before
        the code from 'template' is entered.
        """
        assert isinstance(template, str)
        assert declType is None or isinstance(declType, CGThing)
        assert holderType is None or isinstance(holderType, CGThing)
        self.template = template
        self.declType = declType
        self.holderType = holderType
        self.dealWithOptional = dealWithOptional
        self.declArgs = declArgs
        self.holderArgs = holderArgs


def getHandleDefault(defaultValue):
    tag = defaultValue.type.tag()
    if tag in numericSuffixes:
        # Some numeric literals require a suffix to compile without warnings
        return numericValue(tag, defaultValue.value)
    assert tag == IDLType.Tags.bool
    return toStringBool(defaultValue.value)


def handleDefaultStringValue(defaultValue, method):
    """
    Returns a string which ends up calling 'method' with a (char_t*, length)
    pair that sets this string default value.  This string is suitable for
    passing as the second argument of handleDefault.
    """
    assert (
        defaultValue.type.isDOMString()
        or defaultValue.type.isUSVString()
        or defaultValue.type.isUTF8String()
        or defaultValue.type.isByteString()
    )
    # There shouldn't be any non-ASCII or embedded nulls in here; if
    # it ever sneaks in we will need to think about how to properly
    # represent that in the C++.
    assert all(ord(c) < 128 and ord(c) > 0 for c in defaultValue.value)
    if defaultValue.type.isByteString() or defaultValue.type.isUTF8String():
        prefix = ""
    else:
        prefix = "u"
    return fill(
        """
        ${method}(${prefix}"${value}");
        """,
        method=method,
        prefix=prefix,
        value=defaultValue.value,
    )


def recordKeyType(recordType):
    assert recordType.keyType.isString()
    if recordType.keyType.isByteString() or recordType.keyType.isUTF8String():
        return "nsCString"
    return "nsString"


def recordKeyDeclType(recordType):
    return CGGeneric(recordKeyType(recordType))


def initializerForType(type):
    """
    Get the right initializer for the given type for a data location where we
    plan to then initialize it from a JS::Value.  Some types need to always be
    initialized even before we start the JS::Value-to-IDL-value conversion.

    Returns a string or None if no initialization is needed.
    """
    if type.isObject():
        return "nullptr"
    # We could probably return CGDictionary.getNonInitializingCtorArg() for the
    # dictionary case, but code outside DictionaryBase subclasses can't use
    # that, so we can't do it across the board.
    return None


# If this function is modified, modify CGNativeMember.getArg and
# CGNativeMember.getRetvalInfo accordingly.  The latter cares about the decltype
# and holdertype we end up using, because it needs to be able to return the code
# that will convert those to the actual return value of the callback function.
def getJSToNativeConversionInfo(
    type,
    descriptorProvider,
    failureCode=None,
    isDefinitelyObject=False,
    isMember=False,
    isOptional=False,
    invalidEnumValueFatal=True,
    defaultValue=None,
    isNullOrUndefined=False,
    isKnownMissing=False,
    exceptionCode=None,
    lenientFloatCode=None,
    allowTreatNonCallableAsNull=False,
    isCallbackReturnValue=False,
    sourceDescription="value",
    nestingLevel="",
):
    """
    Get a template for converting a JS value to a native object based on the
    given type and descriptor.  If failureCode is given, then we're actually
    testing whether we can convert the argument to the desired type.  That
    means that failures to convert due to the JS value being the wrong type of
    value need to use failureCode instead of throwing exceptions.  Failures to
    convert that are due to JS exceptions (from toString or valueOf methods) or
    out of memory conditions need to throw exceptions no matter what
    failureCode is.  However what actually happens when throwing an exception
    can be controlled by exceptionCode.  The only requirement on that is that
    exceptionCode must end up doing a return, and every return from this
    function must happen via exceptionCode if exceptionCode is not None.

    If isDefinitelyObject is True, that means we have a value and the value
    tests true for isObject(), so we have no need to recheck that.

    If isNullOrUndefined is True, that means we have a value and the value
    tests true for isNullOrUndefined(), so we have no need to recheck that.

    If isKnownMissing is True, that means that we are known-missing, and for
    cases when we have a default value we only need to output the default value.

    if isMember is not False, we're being converted from a property of some JS
    object, not from an actual method argument, so we can't rely on our jsval
    being rooted or outliving us in any way.  Callers can pass "Dictionary",
    "Variadic", "Sequence", "Union", or "OwningUnion" to indicate that the conversion
    is for something that is a dictionary member, a variadic argument, a sequence,
    an union, or an owning union respectively.
    XXX Once we swtich *Rooter to Rooted* for Record and Sequence type entirely,
        we could remove "Union" from isMember.

    If isOptional is true, then we are doing conversion of an optional
    argument with no default value.

    invalidEnumValueFatal controls whether an invalid enum value conversion
    attempt will throw (if true) or simply return without doing anything (if
    false).

    If defaultValue is not None, it's the IDL default value for this conversion

    If isEnforceRange is true, we're converting an integer and throwing if the
    value is out of range.

    If isClamp is true, we're converting an integer and clamping if the
    value is out of range.

    If isAllowShared is false, we're converting a buffer source and throwing if
    it is a SharedArrayBuffer or backed by a SharedArrayBuffer.

    If lenientFloatCode is not None, it should be used in cases when
    we're a non-finite float that's not unrestricted.

    If allowTreatNonCallableAsNull is true, then [TreatNonCallableAsNull] and
    [LegacyTreatNonObjectAsNull] extended attributes on nullable callback functions
    will be honored.

    If isCallbackReturnValue is "JSImpl" or "Callback", then the declType may be
    adjusted to make it easier to return from a callback.  Since that type is
    never directly observable by any consumers of the callback code, this is OK.
    Furthermore, if isCallbackReturnValue is "JSImpl", that affects the behavior
    of the FailureFatalCastableObjectUnwrapper conversion; this is used for
    implementing auto-wrapping of JS-implemented return values from a
    JS-implemented interface.

    sourceDescription is a description of what this JS value represents, to be
    used in error reporting.  Callers should assume that it might get placed in
    the middle of a sentence.  If it ends up at the beginning of a sentence, its
    first character will be automatically uppercased.

    The return value from this function is a JSToNativeConversionInfo.
    """
    # If we have a defaultValue then we're not actually optional for
    # purposes of what we need to be declared as.
    assert defaultValue is None or not isOptional

    # Also, we should not have a defaultValue if we know we're an object
    assert not isDefinitelyObject or defaultValue is None

    # And we can't both be an object and be null or undefined
    assert not isDefinitelyObject or not isNullOrUndefined

    isClamp = type.hasClamp()
    isEnforceRange = type.hasEnforceRange()
    isAllowShared = type.hasAllowShared()

    # If exceptionCode is not set, we'll just rethrow the exception we got.
    # Note that we can't just set failureCode to exceptionCode, because setting
    # failureCode will prevent pending exceptions from being set in cases when
    # they really should be!
    if exceptionCode is None:
        exceptionCode = "return false;\n"

    # Unfortunately, .capitalize() on a string will lowercase things inside the
    # string, which we do not want.
    def firstCap(string):
        return string[0].upper() + string[1:]

    # Helper functions for dealing with failures due to the JS value being the
    # wrong type of value
    def onFailureNotAnObject(failureCode):
        return CGGeneric(
            failureCode
            or (
                'cx.ThrowErrorMessage<MSG_NOT_OBJECT>("%s");\n'
                "%s" % (firstCap(sourceDescription), exceptionCode)
            )
        )

    def onFailureBadType(failureCode, typeName):
        return CGGeneric(
            failureCode
            or (
                'cx.ThrowErrorMessage<MSG_DOES_NOT_IMPLEMENT_INTERFACE>("%s", "%s");\n'
                "%s" % (firstCap(sourceDescription), typeName, exceptionCode)
            )
        )

    # It's a failure in the committed-to conversion, not a failure to match up
    # to a type, so we don't want to use failureCode in here. We want to just
    # throw an exception unconditionally.
    def onFailureIsShared():
        return CGGeneric(
            'cx.ThrowErrorMessage<MSG_TYPEDARRAY_IS_SHARED>("%s");\n'
            "%s" % (firstCap(sourceDescription), exceptionCode)
        )

    def onFailureIsLarge():
        return CGGeneric(
            'cx.ThrowErrorMessage<MSG_TYPEDARRAY_IS_LARGE>("%s");\n'
            "%s" % (firstCap(sourceDescription), exceptionCode)
        )

    def onFailureIsResizable():
        return CGGeneric(
            'cx.ThrowErrorMessage<MSG_TYPEDARRAY_IS_RESIZABLE>("%s");\n'
            "%s" % (firstCap(sourceDescription), exceptionCode)
        )

    def onFailureNotCallable(failureCode):
        return CGGeneric(
            failureCode
            or (
                'cx.ThrowErrorMessage<MSG_NOT_CALLABLE>("%s");\n'
                "%s" % (firstCap(sourceDescription), exceptionCode)
            )
        )

    # A helper function for handling default values.  Takes a template
    # body and the C++ code to set the default value and wraps the
    # given template body in handling for the default value.
    def handleDefault(template, setDefault):
        if defaultValue is None:
            return template
        if isKnownMissing:
            return fill(
                """
                {
                  // scope for any temporaries our default value setting needs.
                  $*{setDefault}
                }
                """,
                setDefault=setDefault,
            )
        return fill(
            """
            if ($${haveValue}) {
              $*{templateBody}
            } else {
              $*{setDefault}
            }
            """,
            templateBody=template,
            setDefault=setDefault,
        )

    # A helper function for wrapping up the template body for
    # possibly-nullable objecty stuff
    def wrapObjectTemplate(templateBody, type, codeToSetNull, failureCode=None):
        if isNullOrUndefined and type.nullable():
            # Just ignore templateBody and set ourselves to null.
            # Note that we don't have to worry about default values
            # here either, since we already examined this value.
            return codeToSetNull

        if not isDefinitelyObject:
            # Handle the non-object cases by wrapping up the whole
            # thing in an if cascade.
            if type.nullable():
                elifLine = "} else if (${val}.isNullOrUndefined()) {\n"
                elifBody = codeToSetNull
            else:
                elifLine = ""
                elifBody = ""

            # Note that $${val} below expands to ${val}. This string is
            # used as a template later, and val will be filled in then.
            templateBody = fill(
                """
                if ($${val}.isObject()) {
                  $*{templateBody}
                $*{elifLine}
                  $*{elifBody}
                } else {
                  $*{failureBody}
                }
                """,
                templateBody=templateBody,
                elifLine=elifLine,
                elifBody=elifBody,
                failureBody=onFailureNotAnObject(failureCode).define(),
            )

            if isinstance(defaultValue, IDLNullValue):
                assert type.nullable()  # Parser should enforce this
                templateBody = handleDefault(templateBody, codeToSetNull)
            elif isinstance(defaultValue, IDLEmptySequenceValue):
                # Our caller will handle it
                pass
            else:
                assert defaultValue is None

        return templateBody

    # A helper function for converting things that look like a JSObject*.
    def handleJSObjectType(
        type, isMember, failureCode, exceptionCode, sourceDescription
    ):
        if not isMember or isMember == "Union":
            if isOptional:
                # We have a specialization of Optional that will use a
                # Rooted for the storage here.
                declType = CGGeneric("JS::Handle<JSObject*>")
            else:
                declType = CGGeneric("JS::Rooted<JSObject*>")
            declArgs = "cx"
        else:
            assert isMember in (
                "Sequence",
                "Variadic",
                "Dictionary",
                "OwningUnion",
                "Record",
            )
            # We'll get traced by the sequence or dictionary or union tracer
            declType = CGGeneric("JSObject*")
            declArgs = None
        templateBody = "${declName} = &${val}.toObject();\n"

        # For JS-implemented APIs, we refuse to allow passing objects that the
        # API consumer does not subsume. The extra parens around
        # ($${passedToJSImpl}) suppress unreachable code warnings when
        # $${passedToJSImpl} is the literal `false`.  But Apple is shipping a
        # buggy clang (clang 3.9) in Xcode 8.3, so there even the parens are not
        # enough.  So we manually disable some warnings in clang.
        if (
            not isinstance(descriptorProvider, Descriptor)
            or descriptorProvider.interface.isJSImplemented()
        ):
            templateBody = (
                fill(
                    """
                #ifdef __clang__
                #pragma clang diagnostic push
                #pragma clang diagnostic ignored "-Wunreachable-code"
                #pragma clang diagnostic ignored "-Wunreachable-code-return"
                #endif // __clang__
                if (($${passedToJSImpl}) && !CallerSubsumes($${val})) {
                  cx.ThrowErrorMessage<MSG_PERMISSION_DENIED_TO_PASS_ARG>("${sourceDescription}");
                  $*{exceptionCode}
                }
                #ifdef __clang__
                #pragma clang diagnostic pop
                #endif // __clang__
                """,
                    sourceDescription=sourceDescription,
                    exceptionCode=exceptionCode,
                )
                + templateBody
            )

        setToNullCode = "${declName} = nullptr;\n"
        template = wrapObjectTemplate(templateBody, type, setToNullCode, failureCode)
        return JSToNativeConversionInfo(
            template, declType=declType, dealWithOptional=isOptional, declArgs=declArgs
        )

    def incrementNestingLevel():
        if nestingLevel == "":
            return 1
        return nestingLevel + 1

    assert not (isEnforceRange and isClamp)  # These are mutually exclusive

    if type.isSequence() or type.isObservableArray():
        assert not isEnforceRange and not isClamp and not isAllowShared

        if failureCode is None:
            notSequence = (
                'cx.ThrowErrorMessage<MSG_CONVERSION_ERROR>("%s", "%s");\n'
                "%s"
                % (
                    firstCap(sourceDescription),
                    "sequence" if type.isSequence() else "observable array",
                    exceptionCode,
                )
            )
        else:
            notSequence = failureCode

        nullable = type.nullable()
        # Be very careful not to change "type": we need it later
        if nullable:
            elementType = type.inner.inner
        else:
            elementType = type.inner

        # We want to use auto arrays if we can, but we have to be careful with
        # reallocation behavior for arrays.  In particular, if we use auto
        # arrays for sequences and have a sequence of elements which are
        # themselves sequences or have sequences as members, we have a problem.
        # In that case, resizing the outermost AutoTArray to the right size
        # will memmove its elements, but AutoTArrays are not memmovable and
        # hence will end up with pointers to bogus memory, which is bad.  To
        # deal with this, we typically map WebIDL sequences to our Sequence
        # type, which is in fact memmovable.  The one exception is when we're
        # passing in a sequence directly as an argument without any sort of
        # optional or nullable complexity going on.  In that situation, we can
        # use an AutoSequence instead.  We have to keep using Sequence in the
        # nullable and optional cases because we don't want to leak the
        # AutoSequence type to consumers, which would be unavoidable with
        # Nullable<AutoSequence> or Optional<AutoSequence>.
        if (
            (isMember and isMember != "Union")
            or isOptional
            or nullable
            or isCallbackReturnValue
        ):
            sequenceClass = "Sequence"
        else:
            sequenceClass = "binding_detail::AutoSequence"

        # XXXbz we can't include the index in the sourceDescription, because
        # we don't really have a way to pass one in dynamically at runtime...
        elementInfo = getJSToNativeConversionInfo(
            elementType,
            descriptorProvider,
            isMember="Sequence",
            exceptionCode=exceptionCode,
            lenientFloatCode=lenientFloatCode,
            isCallbackReturnValue=isCallbackReturnValue,
            sourceDescription="element of %s" % sourceDescription,
            nestingLevel=incrementNestingLevel(),
        )
        if elementInfo.dealWithOptional:
            raise TypeError("Shouldn't have optional things in sequences")
        if elementInfo.holderType is not None:
            raise TypeError("Shouldn't need holders for sequences")

        typeName = CGTemplatedType(sequenceClass, elementInfo.declType)
        sequenceType = typeName.define()

        if isMember == "Union" and typeNeedsRooting(type):
            assert not nullable
            typeName = CGTemplatedType(
                "binding_detail::RootedAutoSequence", elementInfo.declType
            )
        elif nullable:
            typeName = CGTemplatedType("Nullable", typeName)

        if nullable:
            arrayRef = "${declName}.SetValue()"
        else:
            arrayRef = "${declName}"

        elementConversion = string.Template(elementInfo.template).substitute(
            {
                "val": "temp" + str(nestingLevel),
                "maybeMutableVal": "&temp" + str(nestingLevel),
                "declName": "slot" + str(nestingLevel),
                # We only need holderName here to handle isExternal()
                # interfaces, which use an internal holder for the
                # conversion even when forceOwningType ends up true.
                "holderName": "tempHolder" + str(nestingLevel),
                "passedToJSImpl": "${passedToJSImpl}",
            }
        )

        elementInitializer = initializerForType(elementType)
        if elementInitializer is None:
            elementInitializer = ""
        else:
            elementInitializer = elementInitializer + ", "

        # NOTE: Keep this in sync with variadic conversions as needed
        templateBody = fill(
            """
            JS::ForOfIterator iter${nestingLevel}(cx);
            if (!iter${nestingLevel}.init($${val}, JS::ForOfIterator::AllowNonIterable)) {
              $*{exceptionCode}
            }
            if (!iter${nestingLevel}.valueIsIterable()) {
              $*{notSequence}
            }
            ${sequenceType} &arr${nestingLevel} = ${arrayRef};
            JS::Rooted<JS::Value> temp${nestingLevel}(cx);
            while (true) {
              bool done${nestingLevel};
              if (!iter${nestingLevel}.next(&temp${nestingLevel}, &done${nestingLevel})) {
                $*{exceptionCode}
              }
              if (done${nestingLevel}) {
                break;
              }
              ${elementType}* slotPtr${nestingLevel} = arr${nestingLevel}.AppendElement(${elementInitializer}mozilla::fallible);
              if (!slotPtr${nestingLevel}) {
                JS_ReportOutOfMemory(cx);
                $*{exceptionCode}
              }
              ${elementType}& slot${nestingLevel} = *slotPtr${nestingLevel};
              $*{elementConversion}
            }
            """,
            exceptionCode=exceptionCode,
            notSequence=notSequence,
            sequenceType=sequenceType,
            arrayRef=arrayRef,
            elementType=elementInfo.declType.define(),
            elementConversion=elementConversion,
            elementInitializer=elementInitializer,
            nestingLevel=str(nestingLevel),
        )

        templateBody = wrapObjectTemplate(
            templateBody, type, "${declName}.SetNull();\n", notSequence
        )
        if isinstance(defaultValue, IDLEmptySequenceValue):
            if type.nullable():
                codeToSetEmpty = "${declName}.SetValue();\n"
            else:
                codeToSetEmpty = (
                    "/* ${declName} array is already empty; nothing to do */\n"
                )
            templateBody = handleDefault(templateBody, codeToSetEmpty)

        declArgs = None
        holderType = None
        holderArgs = None
        # Sequence arguments that might contain traceable things need
        # to get traced
        if typeNeedsRooting(elementType):
            if not isMember:
                holderType = CGTemplatedType("SequenceRooter", elementInfo.declType)
                # If our sequence is nullable, this will set the Nullable to be
                # not-null, but that's ok because we make an explicit SetNull() call
                # on it as needed if our JS value is actually null.
                holderArgs = "cx, &%s" % arrayRef
            elif isMember == "Union":
                declArgs = "cx"

        return JSToNativeConversionInfo(
            templateBody,
            declType=typeName,
            declArgs=declArgs,
            holderType=holderType,
            dealWithOptional=isOptional,
            holderArgs=holderArgs,
        )

    if type.isRecord():
        assert not isEnforceRange and not isClamp and not isAllowShared
        if failureCode is None:
            notRecord = 'cx.ThrowErrorMessage<MSG_NOT_OBJECT>("%s");\n' "%s" % (
                firstCap(sourceDescription),
                exceptionCode,
            )
        else:
            notRecord = failureCode

        nullable = type.nullable()
        # Be very careful not to change "type": we need it later
        if nullable:
            recordType = type.inner
        else:
            recordType = type
        valueType = recordType.inner

        valueInfo = getJSToNativeConversionInfo(
            valueType,
            descriptorProvider,
            isMember="Record",
            exceptionCode=exceptionCode,
            lenientFloatCode=lenientFloatCode,
            isCallbackReturnValue=isCallbackReturnValue,
            sourceDescription="value in %s" % sourceDescription,
            nestingLevel=incrementNestingLevel(),
        )
        if valueInfo.dealWithOptional:
            raise TypeError("Shouldn't have optional things in record")
        if valueInfo.holderType is not None:
            raise TypeError("Shouldn't need holders for record")

        declType = CGTemplatedType(
            "Record", [recordKeyDeclType(recordType), valueInfo.declType]
        )
        typeName = declType.define()

        if isMember == "Union" and typeNeedsRooting(type):
            assert not nullable
            declType = CGTemplatedType(
                "RootedRecord", [recordKeyDeclType(recordType), valueInfo.declType]
            )
        elif nullable:
            declType = CGTemplatedType("Nullable", declType)

        if nullable:
            recordRef = "${declName}.SetValue()"
        else:
            recordRef = "${declName}"

        valueConversion = string.Template(valueInfo.template).substitute(
            {
                "val": "temp",
                "maybeMutableVal": "&temp",
                "declName": "slot",
                # We only need holderName here to handle isExternal()
                # interfaces, which use an internal holder for the
                # conversion even when forceOwningType ends up true.
                "holderName": "tempHolder",
                "passedToJSImpl": "${passedToJSImpl}",
            }
        )

        keyType = recordKeyType(recordType)
        if recordType.keyType.isJSString():
            raise TypeError(
                "Have do deal with JSString record type, but don't know how"
            )
        if recordType.keyType.isByteString() or recordType.keyType.isUTF8String():
            hashKeyType = "nsCStringHashKey"
            if recordType.keyType.isByteString():
                keyConversionFunction = "ConvertJSValueToByteString"
            else:
                keyConversionFunction = "ConvertJSValueToString"

        else:
            hashKeyType = "nsStringHashKey"
            if recordType.keyType.isDOMString():
                keyConversionFunction = "ConvertJSValueToString"
            else:
                assert recordType.keyType.isUSVString()
                keyConversionFunction = "ConvertJSValueToUSVString"

        templateBody = fill(
            """
            auto& recordEntries = ${recordRef}.Entries();

            JS::Rooted<JSObject*> recordObj(cx, &$${val}.toObject());
            JS::RootedVector<jsid> ids(cx);
            if (!js::GetPropertyKeys(cx, recordObj,
                                     JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS, &ids)) {
              $*{exceptionCode}
            }
            if (!recordEntries.SetCapacity(ids.length(), mozilla::fallible)) {
              JS_ReportOutOfMemory(cx);
              $*{exceptionCode}
            }
            JS::Rooted<JS::Value> propNameValue(cx);
            JS::Rooted<JS::Value> temp(cx);
            JS::Rooted<jsid> curId(cx);
            JS::Rooted<JS::Value> idVal(cx);
            // Use a hashset to keep track of ids seen, to avoid
            // introducing nasty O(N^2) behavior scanning for them all the
            // time.  Ideally we'd use a data structure with O(1) lookup
            // _and_ ordering for the MozMap, but we don't have one lying
            // around.
            nsTHashtable<${hashKeyType}> idsSeen;
            for (size_t i = 0; i < ids.length(); ++i) {
              curId = ids[i];

              JS::Rooted<mozilla::Maybe<JS::PropertyDescriptor>> desc(cx);
              if (!JS_GetOwnPropertyDescriptorById(cx, recordObj, curId,
                                                   &desc)) {
                $*{exceptionCode}
              }

              if (desc.isNothing() || !desc->enumerable()) {
                continue;
              }

              idVal = js::IdToValue(curId);
              ${keyType} propName;
              // This will just throw if idVal is a Symbol, like the spec says
              // to do.
              if (!${keyConversionFunction}(cx, idVal, "key of ${sourceDescription}", propName)) {
                $*{exceptionCode}
              }

              if (!JS_GetPropertyById(cx, recordObj, curId, &temp)) {
                $*{exceptionCode}
              }

              ${typeName}::EntryType* entry;
              if (!idsSeen.EnsureInserted(propName)) {
                // Find the existing entry.
                auto idx = recordEntries.IndexOf(propName);
                MOZ_ASSERT(idx != recordEntries.NoIndex,
                           "Why is it not found?");
                // Now blow it away to make it look like it was just added
                // to the array, because it's not obvious that it's
                // safe to write to its already-initialized mValue via our
                // normal codegen conversions.  For example, the value
                // could be a union and this would change its type, but
                // codegen assumes we won't do that.
                entry = recordEntries.ReconstructElementAt(idx);
              } else {
                // Safe to do an infallible append here, because we did a
                // SetCapacity above to the right capacity.
                entry = recordEntries.AppendElement();
              }
              entry->mKey = propName;
              ${valueType}& slot = entry->mValue;
              $*{valueConversion}
            }
            """,
            exceptionCode=exceptionCode,
            recordRef=recordRef,
            hashKeyType=hashKeyType,
            keyType=keyType,
            keyConversionFunction=keyConversionFunction,
            sourceDescription=sourceDescription,
            typeName=typeName,
            valueType=valueInfo.declType.define(),
            valueConversion=valueConversion,
        )

        templateBody = wrapObjectTemplate(
            templateBody, type, "${declName}.SetNull();\n", notRecord
        )

        declArgs = None
        holderType = None
        holderArgs = None
        # record arguments that might contain traceable things need
        # to get traced
        if not isMember and isCallbackReturnValue:
            # Go ahead and just convert directly into our actual return value
            declType = CGWrapper(declType, post="&")
            declArgs = "aRetVal"
        elif typeNeedsRooting(valueType):
            if not isMember:
                holderType = CGTemplatedType(
                    "RecordRooter", [recordKeyDeclType(recordType), valueInfo.declType]
                )
                # If our record is nullable, this will set the Nullable to be
                # not-null, but that's ok because we make an explicit SetNull() call
                # on it as needed if our JS value is actually null.
                holderArgs = "cx, &%s" % recordRef
            elif isMember == "Union":
                declArgs = "cx"

        return JSToNativeConversionInfo(
            templateBody,
            declType=declType,
            declArgs=declArgs,
            holderType=holderType,
            dealWithOptional=isOptional,
            holderArgs=holderArgs,
        )

    if type.isUnion():
        nullable = type.nullable()
        if nullable:
            type = type.inner

        isOwningUnion = (isMember and isMember != "Union") or isCallbackReturnValue
        unionArgumentObj = "${declName}"
        if nullable:
            if isOptional and not isOwningUnion:
                unionArgumentObj += ".Value()"
            # If we're owning, we're a Nullable, which hasn't been told it has
            # a value.  Otherwise we're an already-constructed Maybe.
            unionArgumentObj += ".SetValue()"

        templateBody = CGIfWrapper(
            CGGeneric(exceptionCode),
            '!%s.Init(cx, ${val}, "%s", ${passedToJSImpl})'
            % (unionArgumentObj, firstCap(sourceDescription)),
        )

        if type.hasNullableType:
            assert not nullable
            # Make sure to handle a null default value here
            if defaultValue and isinstance(defaultValue, IDLNullValue):
                assert defaultValue.type == type
                templateBody = CGIfElseWrapper(
                    "!(${haveValue})",
                    CGGeneric("%s.SetNull();\n" % unionArgumentObj),
                    templateBody,
                )

        typeName = CGUnionStruct.unionTypeDecl(type, isOwningUnion)
        argumentTypeName = typeName + "Argument"
        if nullable:
            typeName = "Nullable<" + typeName + " >"

        declType = CGGeneric(typeName)
        if isOwningUnion:
            holderType = None
        else:
            holderType = CGGeneric(argumentTypeName)
            if nullable:
                holderType = CGTemplatedType("Maybe", holderType)

        # If we're isOptional and not nullable the normal optional handling will
        # handle lazy construction of our holder.  If we're nullable and not
        # owning we do it all by hand because we do not want our holder
        # constructed if we're null.  But if we're owning we don't have a
        # holder anyway, so we can do the normal Optional codepath.
        declLoc = "${declName}"
        constructDecl = None
        if nullable:
            if isOptional and not isOwningUnion:
                declType = CGTemplatedType("Optional", declType)
                constructDecl = CGGeneric("${declName}.Construct();\n")
                declLoc = "${declName}.Value()"

        if not isMember and isCallbackReturnValue:
            declType = CGWrapper(declType, post="&")
            declArgs = "aRetVal"
        else:
            declArgs = None

        if (
            defaultValue
            and not isinstance(defaultValue, IDLNullValue)
            and not isinstance(defaultValue, IDLDefaultDictionaryValue)
        ):
            tag = defaultValue.type.tag()

            if tag in numericSuffixes or tag is IDLType.Tags.bool:
                defaultStr = getHandleDefault(defaultValue)
                # Make sure we actually construct the thing inside the nullable.
                value = declLoc + (".SetValue()" if nullable else "")
                name = getUnionMemberName(defaultValue.type)
                default = CGGeneric(
                    "%s.RawSetAs%s() = %s;\n" % (value, name, defaultStr)
                )
            elif isinstance(defaultValue, IDLEmptySequenceValue):
                name = getUnionMemberName(defaultValue.type)
                # Make sure we actually construct the thing inside the nullable.
                value = declLoc + (".SetValue()" if nullable else "")
                if not isOwningUnion and typeNeedsRooting(defaultValue.type):
                    ctorArgs = "cx"
                else:
                    ctorArgs = ""
                # It's enough to set us to the right type; that will
                # create an empty array, which is all we need here.
                default = CGGeneric(
                    "Unused << %s.RawSetAs%s(%s);\n" % (value, name, ctorArgs)
                )
            elif defaultValue.type.isEnum():
                name = getUnionMemberName(defaultValue.type)
                # Make sure we actually construct the thing inside the nullable.
                value = declLoc + (".SetValue()" if nullable else "")
                default = CGGeneric(
                    "%s.RawSetAs%s() = %s::%s;\n"
                    % (
                        value,
                        name,
                        defaultValue.type.inner.identifier.name,
                        getEnumValueName(defaultValue.value),
                    )
                )
            else:
                default = CGGeneric(
                    handleDefaultStringValue(
                        defaultValue, "%s.SetStringLiteral" % unionArgumentObj
                    )
                )

            templateBody = CGIfElseWrapper("!(${haveValue})", default, templateBody)

        if nullable:
            assert not type.hasNullableType
            if defaultValue:
                if isinstance(defaultValue, IDLNullValue):
                    extraConditionForNull = "!(${haveValue}) || "
                else:
                    extraConditionForNull = "(${haveValue}) && "
            else:
                extraConditionForNull = ""

            hasUndefinedType = any(t.isUndefined() for t in type.flatMemberTypes)
            assert not hasUndefinedType or defaultValue is None

            nullTest = (
                "${val}.isNull()" if hasUndefinedType else "${val}.isNullOrUndefined()"
            )
            templateBody = CGIfElseWrapper(
                extraConditionForNull + nullTest,
                CGGeneric("%s.SetNull();\n" % declLoc),
                templateBody,
            )
        elif (
            not type.hasNullableType
            and defaultValue
            and isinstance(defaultValue, IDLDefaultDictionaryValue)
        ):
            assert type.hasDictionaryType()
            assert defaultValue.type.isDictionary()
            if not isOwningUnion and typeNeedsRooting(defaultValue.type):
                ctorArgs = "cx"
            else:
                ctorArgs = ""
            initDictionaryWithNull = CGIfWrapper(
                CGGeneric("return false;\n"),
                (
                    '!%s.RawSetAs%s(%s).Init(cx, JS::NullHandleValue, "Member of %s")'
                    % (
                        declLoc,
                        getUnionMemberName(defaultValue.type),
                        ctorArgs,
                        type.prettyName(),
                    )
                ),
            )
            templateBody = CGIfElseWrapper(
                "!(${haveValue})", initDictionaryWithNull, templateBody
            )

        templateBody = CGList([constructDecl, templateBody])

        return JSToNativeConversionInfo(
            templateBody.define(),
            declType=declType,
            declArgs=declArgs,
            dealWithOptional=isOptional and (not nullable or isOwningUnion),
        )

    if type.isPromise():
        assert not type.nullable()
        assert defaultValue is None

        # We always have to hold a strong ref to Promise here, because
        # Promise::resolve returns an addrefed thing.
        argIsPointer = isCallbackReturnValue
        if argIsPointer:
            declType = CGGeneric("RefPtr<Promise>")
        else:
            declType = CGGeneric("OwningNonNull<Promise>")

        # Per spec, what we're supposed to do is take the original
        # Promise.resolve and call it with the original Promise as this
        # value to make a Promise out of whatever value we actually have
        # here.  The question is which global we should use.  There are
        # several cases to consider:
        #
        # 1) Normal call to API with a Promise argument.  This is a case the
        #    spec covers, and we should be using the current Realm's
        #    Promise.  That means the current compartment.
        # 2) Call to API with a Promise argument over Xrays.  In practice,
        #    this sort of thing seems to be used for giving an API
        #    implementation a way to wait for conclusion of an asyc
        #    operation, _not_ to expose the Promise to content code.  So we
        #    probably want to allow callers to use such an API in a
        #    "natural" way, by passing chrome-side promises; indeed, that
        #    may be all that the caller has to represent their async
        #    operation.  That means we really need to do the
        #    Promise.resolve() in the caller (chrome) compartment: if we do
        #    it in the content compartment, we will try to call .then() on
        #    the chrome promise while in the content compartment, which will
        #    throw and we'll just get a rejected Promise.  Note that this is
        #    also the reason why a caller who has a chrome Promise
        #    representing an async operation can't itself convert it to a
        #    content-side Promise (at least not without some serious
        #    gyrations).
        # 3) Promise return value from a callback or callback interface.
        #    Per spec, this should use the Realm of the callback object.  In
        #    our case, that's the compartment of the underlying callback,
        #    not the current compartment (which may be the compartment of
        #    some cross-compartment wrapper around said callback).
        # 4) Return value from a JS-implemented interface.  In this case we
        #    have a problem.  Our current compartment is the compartment of
        #    the JS implementation.  But if the JS implementation returned
        #    a page-side Promise (which is a totally sane thing to do, and
        #    in fact the right thing to do given that this return value is
        #    going right to content script) then we don't want to
        #    Promise.resolve with our current compartment Promise, because
        #    that will wrap it up in a chrome-side Promise, which is
        #    decidedly _not_ what's desired here.  So in that case we
        #    should really unwrap the return value and use the global of
        #    the result.  CheckedUnwrapStatic should be good enough for that;
        #    if it fails, then we're failing unwrap while in a
        #    system-privileged compartment, so presumably we have a dead
        #    object wrapper.  Just error out.  Do NOT fall back to using
        #    the current compartment instead: that will return a
        #    system-privileged rejected (because getting .then inside
        #    resolve() failed) Promise to the caller, which they won't be
        #    able to touch.  That's not helpful.  If we error out, on the
        #    other hand, they will get a content-side rejected promise.
        #    Same thing if the value returned is not even an object.
        if isCallbackReturnValue == "JSImpl":
            # Case 4 above.  Note that globalObj defaults to the current
            # compartment global.  Note that we don't use $*{exceptionCode}
            # here because that will try to aRv.Throw(NS_ERROR_UNEXPECTED)
            # which we don't really want here.
            assert exceptionCode == "aRv.Throw(NS_ERROR_UNEXPECTED);\nreturn nullptr;\n"
            getPromiseGlobal = fill(
                """
                if (!$${val}.isObject()) {
                  aRv.ThrowTypeError<MSG_NOT_OBJECT>("${sourceDescription}");
                  return nullptr;
                }
                JSObject* unwrappedVal = js::CheckedUnwrapStatic(&$${val}.toObject());
                if (!unwrappedVal) {
                  // A slight lie, but not much of one, for a dead object wrapper.
                  aRv.ThrowTypeError<MSG_NOT_OBJECT>("${sourceDescription}");
                  return nullptr;
                }
                globalObj = JS::GetNonCCWObjectGlobal(unwrappedVal);
                """,
                sourceDescription=sourceDescription,
            )
        elif isCallbackReturnValue == "Callback":
            getPromiseGlobal = dedent(
                """
                // We basically want our entry global here.  Play it safe
                // and use GetEntryGlobal() to get it, with whatever
                // principal-clamping it ends up doing.
                globalObj = GetEntryGlobal()->GetGlobalJSObject();
                """
            )
        else:
            getPromiseGlobal = dedent(
                """
                globalObj = JS::CurrentGlobalOrNull(cx);
                """
            )

        templateBody = fill(
            """
            { // Scope for our GlobalObject, FastErrorResult, JSAutoRealm,
              // etc.

              JS::Rooted<JSObject*> globalObj(cx);
              $*{getPromiseGlobal}
              JSAutoRealm ar(cx, globalObj);
              GlobalObject promiseGlobal(cx, globalObj);
              if (promiseGlobal.Failed()) {
                $*{exceptionCode}
              }

              JS::Rooted<JS::Value> valueToResolve(cx, $${val});
              if (!JS_WrapValue(cx, &valueToResolve)) {
                $*{exceptionCode}
              }
              binding_detail::FastErrorResult promiseRv;
              nsCOMPtr<nsIGlobalObject> global =
                do_QueryInterface(promiseGlobal.GetAsSupports());
              if (!global) {
                promiseRv.Throw(NS_ERROR_UNEXPECTED);
                MOZ_ALWAYS_TRUE(promiseRv.MaybeSetPendingException(cx));
                $*{exceptionCode}
              }
              $${declName} = Promise::Resolve(global, cx, valueToResolve,
                                              promiseRv);
              if (promiseRv.MaybeSetPendingException(cx)) {
                $*{exceptionCode}
              }
            }
            """,
            getPromiseGlobal=getPromiseGlobal,
            exceptionCode=exceptionCode,
        )

        return JSToNativeConversionInfo(
            templateBody, declType=declType, dealWithOptional=isOptional
        )

    if type.isGeckoInterface():
        assert not isEnforceRange and not isClamp and not isAllowShared

        descriptor = descriptorProvider.getDescriptor(
            type.unroll().inner.identifier.name
        )

        assert descriptor.nativeType != "JSObject"

        if descriptor.interface.isCallback():
            (declType, declArgs, conversion) = getCallbackConversionInfo(
                type, descriptor.interface, isMember, isCallbackReturnValue, isOptional
            )
            template = wrapObjectTemplate(
                conversion, type, "${declName} = nullptr;\n", failureCode
            )
            return JSToNativeConversionInfo(
                template,
                declType=declType,
                declArgs=declArgs,
                dealWithOptional=isOptional,
            )

        if descriptor.interface.identifier.name == "WindowProxy":
            declType = CGGeneric("mozilla::dom::WindowProxyHolder")
            if type.nullable():
                declType = CGTemplatedType("Nullable", declType)
                windowProxyHolderRef = "${declName}.SetValue()"
            else:
                windowProxyHolderRef = "${declName}"

            failureCode = onFailureBadType(
                failureCode, descriptor.interface.identifier.name
            ).define()
            templateBody = fill(
                """
                JS::Rooted<JSObject*> source(cx, &$${val}.toObject());
                if (NS_FAILED(UnwrapWindowProxyArg(cx, source, ${windowProxyHolderRef}))) {
                    $*{onFailure}
                }
                """,
                windowProxyHolderRef=windowProxyHolderRef,
                onFailure=failureCode,
            )
            templateBody = wrapObjectTemplate(
                templateBody, type, "${declName}.SetNull();\n", failureCode
            )
            return JSToNativeConversionInfo(
                templateBody, declType=declType, dealWithOptional=isOptional
            )

        # This is an interface that we implement as a concrete class
        # or an XPCOM interface.

        # Allow null pointers for nullable types and old-binding classes, and
        # use an RefPtr or raw pointer for callback return values to make
        # them easier to return.
        argIsPointer = (
            type.nullable() or type.unroll().inner.isExternal() or isCallbackReturnValue
        )

        # Sequence and dictionary members, as well as owning unions (which can
        # appear here as return values in JS-implemented interfaces) have to
        # hold a strong ref to the thing being passed down.  Those all set
        # isMember.
        #
        # Also, callback return values always end up addrefing anyway, so there
        # is no point trying to avoid it here and it makes other things simpler
        # since we can assume the return value is a strong ref.
        assert not descriptor.interface.isCallback()
        forceOwningType = (isMember and isMember != "Union") or isCallbackReturnValue

        typeName = descriptor.nativeType
        typePtr = typeName + "*"

        # Compute a few things:
        #  - declType is the type we want to return as the first element of our
        #    tuple.
        #  - holderType is the type we want to return as the third element
        #    of our tuple.

        # Set up some sensible defaults for these things insofar as we can.
        holderType = None
        if argIsPointer:
            if forceOwningType:
                declType = "RefPtr<" + typeName + ">"
            else:
                declType = typePtr
        else:
            if forceOwningType:
                declType = "OwningNonNull<" + typeName + ">"
            else:
                declType = "NonNull<" + typeName + ">"

        templateBody = ""
        if forceOwningType:
            templateBody += fill(
                """
                static_assert(IsRefcounted<${typeName}>::value, "We can only store refcounted classes.");
                """,
                typeName=typeName,
            )

        if not descriptor.interface.isExternal():
            if failureCode is not None:
                templateBody += str(
                    CastableObjectUnwrapper(
                        descriptor,
                        "${val}",
                        "${maybeMutableVal}",
                        "${declName}",
                        failureCode,
                    )
                )
            else:
                templateBody += str(
                    FailureFatalCastableObjectUnwrapper(
                        descriptor,
                        "${val}",
                        "${maybeMutableVal}",
                        "${declName}",
                        exceptionCode,
                        isCallbackReturnValue,
                        firstCap(sourceDescription),
                    )
                )
        else:
            # External interface.  We always have a holder for these, because we
            # don't actually know whether we have to addref when unwrapping or not.
            # So we just pass an getter_AddRefs(RefPtr) to XPConnect and if we'll
            # need a release it'll put a non-null pointer in there.
            if forceOwningType:
                # Don't return a holderType in this case; our declName
                # will just own stuff.
                templateBody += "RefPtr<" + typeName + "> ${holderName};\n"
            else:
                holderType = "RefPtr<" + typeName + ">"
            templateBody += (
                "JS::Rooted<JSObject*> source(cx, &${val}.toObject());\n"
                + "if (NS_FAILED(UnwrapArg<"
                + typeName
                + ">(cx, source, getter_AddRefs(${holderName})))) {\n"
            )
            templateBody += CGIndenter(
                onFailureBadType(failureCode, descriptor.interface.identifier.name)
            ).define()
            templateBody += "}\n" "MOZ_ASSERT(${holderName});\n"

            # And store our value in ${declName}
            templateBody += "${declName} = ${holderName};\n"

        # Just pass failureCode, not onFailureBadType, here, so we'll report
        # the thing as not an object as opposed to not implementing whatever
        # our interface is.
        templateBody = wrapObjectTemplate(
            templateBody, type, "${declName} = nullptr;\n", failureCode
        )

        declType = CGGeneric(declType)
        if holderType is not None:
            holderType = CGGeneric(holderType)
        return JSToNativeConversionInfo(
            templateBody,
            declType=declType,
            holderType=holderType,
            dealWithOptional=isOptional,
        )

    if type.isSpiderMonkeyInterface():
        assert not isEnforceRange and not isClamp
        name = type.unroll().name  # unroll() because it may be nullable
        interfaceType = CGGeneric(name)
        declType = interfaceType
        if type.nullable():
            declType = CGTemplatedType("Nullable", declType)
            objRef = "${declName}.SetValue()"
        else:
            objRef = "${declName}"

        # Again, this is a bit strange since we are actually building a
        # template string here. ${objRef} and $*{badType} below are filled in
        # right now; $${val} expands to ${val}, to be filled in later.
        template = fill(
            """
            if (!${objRef}.Init(&$${val}.toObject())) {
              $*{badType}
            }
            """,
            objRef=objRef,
            badType=onFailureBadType(failureCode, type.name).define(),
        )
        if type.isBufferSource():
            if type.isArrayBuffer():
                isSharedMethod = "JS::IsSharedArrayBufferObject"
                isLargeMethod = "JS::IsLargeArrayBufferMaybeShared"
                isResizableMethod = "JS::IsResizableArrayBufferMaybeShared"
            else:
                assert type.isArrayBufferView() or type.isTypedArray()
                isSharedMethod = "JS::IsArrayBufferViewShared"
                isLargeMethod = "JS::IsLargeArrayBufferView"
                isResizableMethod = "JS::IsResizableArrayBufferView"
            if not isAllowShared:
                template += fill(
                    """
                    if (${isSharedMethod}(${objRef}.Obj())) {
                      $*{badType}
                    }
                    """,
                    isSharedMethod=isSharedMethod,
                    objRef=objRef,
                    badType=onFailureIsShared().define(),
                )
            # For now reject large (> 2 GB) ArrayBuffers and ArrayBufferViews.
            # Supporting this will require changing dom::TypedArray and
            # consumers.
            template += fill(
                """
                if (${isLargeMethod}(${objRef}.Obj())) {
                  $*{badType}
                }
                """,
                isLargeMethod=isLargeMethod,
                objRef=objRef,
                badType=onFailureIsLarge().define(),
            )
            # For now reject resizable ArrayBuffers and growable
            # SharedArrayBuffers. Supporting this will require changing
            # dom::TypedArray and consumers.
            template += fill(
                """
                if (${isResizableMethod}(${objRef}.Obj())) {
                  $*{badType}
                }
                """,
                isResizableMethod=isResizableMethod,
                objRef=objRef,
                badType=onFailureIsResizable().define(),
            )
        template = wrapObjectTemplate(
            template, type, "${declName}.SetNull();\n", failureCode
        )
        if not isMember or isMember == "Union":
            # This is a bit annoying.  In a union we don't want to have a
            # holder, since unions don't support that.  But if we're optional we
            # want to have a holder, so that the callee doesn't see
            # Optional<RootedSpiderMonkeyInterface<InterfaceType>>.  So do a
            # holder if we're optional and use a RootedSpiderMonkeyInterface
            # otherwise.
            if isOptional:
                holderType = CGTemplatedType(
                    "SpiderMonkeyInterfaceRooter", interfaceType
                )
                # If our SpiderMonkey interface is nullable, this will set the
                # Nullable to be not-null, but that's ok because we make an
                # explicit SetNull() call on it as needed if our JS value is
                # actually null.  XXXbz Because "Maybe" takes const refs for
                # constructor arguments, we can't pass a reference here; have
                # to pass a pointer.
                holderArgs = "cx, &%s" % objRef
                declArgs = None
            else:
                holderType = None
                holderArgs = None
                declType = CGTemplatedType("RootedSpiderMonkeyInterface", declType)
                declArgs = "cx"
        else:
            holderType = None
            holderArgs = None
            declArgs = None
        return JSToNativeConversionInfo(
            template,
            declType=declType,
            holderType=holderType,
            dealWithOptional=isOptional,
            declArgs=declArgs,
            holderArgs=holderArgs,
        )

    if type.isJSString():
        assert not isEnforceRange and not isClamp and not isAllowShared
        if type.nullable():
            raise TypeError("Nullable JSString not supported")

        declArgs = "cx"
        if isMember:
            raise TypeError("JSString not supported as member")
        else:
            declType = "JS::Rooted<JSString*>"

        if isOptional:
            raise TypeError("JSString not supported as optional")
        templateBody = fill(
            """
                if (!($${declName} = ConvertJSValueToJSString(cx, $${val}))) {
                  $*{exceptionCode}
                }
                """,
            exceptionCode=exceptionCode,
        )

        if defaultValue is not None:
            assert not isinstance(defaultValue, IDLNullValue)
            defaultCode = fill(
                """
                static const char data[] = { ${data} };
                $${declName} = JS_NewStringCopyN(cx, data, std::size(data) - 1);
                if (!$${declName}) {
                    $*{exceptionCode}
                }
                """,
                data=", ".join(
                    ["'" + char + "'" for char in defaultValue.value] + ["0"]
                ),
                exceptionCode=exceptionCode,
            )

            templateBody = handleDefault(templateBody, defaultCode)
        return JSToNativeConversionInfo(
            templateBody, declType=CGGeneric(declType), declArgs=declArgs
        )

    if type.isDOMString() or type.isUSVString() or type.isUTF8String():
        assert not isEnforceRange and not isClamp and not isAllowShared

        treatAs = {
            "Default": "eStringify",
            "EmptyString": "eEmpty",
            "Null": "eNull",
        }
        if type.nullable():
            # For nullable strings null becomes a null string.
            treatNullAs = "Null"
            # For nullable strings undefined also becomes a null string.
            undefinedBehavior = "eNull"
        else:
            undefinedBehavior = "eStringify"
            if type.legacyNullToEmptyString:
                treatNullAs = "EmptyString"
            else:
                treatNullAs = "Default"
        nullBehavior = treatAs[treatNullAs]

        def getConversionCode(varName):
            normalizeCode = ""
            if type.isUSVString():
                normalizeCode = fill(
                    """
                    if (!NormalizeUSVString(${var})) {
                      JS_ReportOutOfMemory(cx);
                      $*{exceptionCode}
                    }
                    """,
                    var=varName,
                    exceptionCode=exceptionCode,
                )

            conversionCode = fill(
                """
                if (!ConvertJSValueToString(cx, $${val}, ${nullBehavior}, ${undefinedBehavior}, ${varName})) {
                  $*{exceptionCode}
                }
                $*{normalizeCode}
                """,
                nullBehavior=nullBehavior,
                undefinedBehavior=undefinedBehavior,
                varName=varName,
                exceptionCode=exceptionCode,
                normalizeCode=normalizeCode,
            )

            if defaultValue is None:
                return conversionCode

            if isinstance(defaultValue, IDLNullValue):
                assert type.nullable()
                defaultCode = "%s.SetIsVoid(true);\n" % varName
            else:
                defaultCode = handleDefaultStringValue(
                    defaultValue, "%s.AssignLiteral" % varName
                )
            return handleDefault(conversionCode, defaultCode)

        if isMember and isMember != "Union":
            # Convert directly into the ns[C]String member we have.
            if type.isUTF8String():
                declType = "nsCString"
            else:
                declType = "nsString"
            return JSToNativeConversionInfo(
                getConversionCode("${declName}"),
                declType=CGGeneric(declType),
                dealWithOptional=isOptional,
            )

        if isOptional:
            if type.isUTF8String():
                declType = "Optional<nsACString>"
                holderType = CGGeneric("binding_detail::FakeString<char>")
            else:
                declType = "Optional<nsAString>"
                holderType = CGGeneric("binding_detail::FakeString<char16_t>")
            conversionCode = "%s" "${declName} = &${holderName};\n" % getConversionCode(
                "${holderName}"
            )
        else:
            if type.isUTF8String():
                declType = "binding_detail::FakeString<char>"
            else:
                declType = "binding_detail::FakeString<char16_t>"
            holderType = None
            conversionCode = getConversionCode("${declName}")

        # No need to deal with optional here; we handled it already
        return JSToNativeConversionInfo(
            conversionCode, declType=CGGeneric(declType), holderType=holderType
        )

    if type.isByteString():
        assert not isEnforceRange and not isClamp and not isAllowShared

        nullable = toStringBool(type.nullable())

        conversionCode = fill(
            """
            if (!ConvertJSValueToByteString(cx, $${val}, ${nullable}, "${sourceDescription}", $${declName})) {
              $*{exceptionCode}
            }
            """,
            nullable=nullable,
            sourceDescription=sourceDescription,
            exceptionCode=exceptionCode,
        )

        if defaultValue is not None:
            if isinstance(defaultValue, IDLNullValue):
                assert type.nullable()
                defaultCode = "${declName}.SetIsVoid(true);\n"
            else:
                defaultCode = handleDefaultStringValue(
                    defaultValue, "${declName}.AssignLiteral"
                )
            conversionCode = handleDefault(conversionCode, defaultCode)

        return JSToNativeConversionInfo(
            conversionCode, declType=CGGeneric("nsCString"), dealWithOptional=isOptional
        )

    if type.isEnum():
        assert not isEnforceRange and not isClamp and not isAllowShared

        enumName = type.unroll().inner.identifier.name
        declType = CGGeneric(enumName)
        if type.nullable():
            declType = CGTemplatedType("Nullable", declType)
            declType = declType.define()
            enumLoc = "${declName}.SetValue()"
        else:
            enumLoc = "${declName}"
            declType = declType.define()

        if invalidEnumValueFatal:
            handleInvalidEnumValueCode = "MOZ_ASSERT(index >= 0);\n"
        else:
            # invalidEnumValueFatal is false only for attributes.  So we won't
            # have a non-default exceptionCode here unless attribute "arg
            # conversion" code starts passing in an exceptionCode.  At which
            # point we'll need to figure out what that even means.
            assert exceptionCode == "return false;\n"
            handleInvalidEnumValueCode = dedent(
                """
                if (index < 0) {
                  return true;
                }
                """
            )

        template = fill(
            """
            {
              int index;
              if (!binding_detail::FindEnumStringIndex<${invalidEnumValueFatal}>(cx, $${val},
                                                                                 binding_detail::EnumStrings<${enumtype}>::Values,
                                                                                 "${enumtype}", "${sourceDescription}",
                                                                                 &index)) {
                $*{exceptionCode}
              }
              $*{handleInvalidEnumValueCode}
              ${enumLoc} = static_cast<${enumtype}>(index);
            }
            """,
            enumtype=enumName,
            invalidEnumValueFatal=toStringBool(invalidEnumValueFatal),
            handleInvalidEnumValueCode=handleInvalidEnumValueCode,
            exceptionCode=exceptionCode,
            enumLoc=enumLoc,
            sourceDescription=sourceDescription,
        )

        setNull = "${declName}.SetNull();\n"

        if type.nullable():
            template = CGIfElseWrapper(
                "${val}.isNullOrUndefined()", CGGeneric(setNull), CGGeneric(template)
            ).define()

        if defaultValue is not None:
            if isinstance(defaultValue, IDLNullValue):
                assert type.nullable()
                template = handleDefault(template, setNull)
            else:
                assert defaultValue.type.tag() == IDLType.Tags.domstring
                template = handleDefault(
                    template,
                    (
                        "%s = %s::%s;\n"
                        % (enumLoc, enumName, getEnumValueName(defaultValue.value))
                    ),
                )
        return JSToNativeConversionInfo(
            template, declType=CGGeneric(declType), dealWithOptional=isOptional
        )

    if type.isCallback():
        assert not isEnforceRange and not isClamp and not isAllowShared
        assert not type.treatNonCallableAsNull() or type.nullable()
        assert not type.treatNonObjectAsNull() or type.nullable()
        assert not type.treatNonObjectAsNull() or not type.treatNonCallableAsNull()

        callback = type.unroll().callback
        name = callback.identifier.name
        (declType, declArgs, conversion) = getCallbackConversionInfo(
            type, callback, isMember, isCallbackReturnValue, isOptional
        )

        if allowTreatNonCallableAsNull and type.treatNonCallableAsNull():
            haveCallable = "JS::IsCallable(&${val}.toObject())"
            if not isDefinitelyObject:
                haveCallable = "${val}.isObject() && " + haveCallable
            if defaultValue is not None:
                assert isinstance(defaultValue, IDLNullValue)
                haveCallable = "(${haveValue}) && " + haveCallable
            template = (
                ("if (%s) {\n" % haveCallable) + conversion + "} else {\n"
                "  ${declName} = nullptr;\n"
                "}\n"
            )
        elif allowTreatNonCallableAsNull and type.treatNonObjectAsNull():
            if not isDefinitelyObject:
                haveObject = "${val}.isObject()"
                if defaultValue is not None:
                    assert isinstance(defaultValue, IDLNullValue)
                    haveObject = "(${haveValue}) && " + haveObject
                template = CGIfElseWrapper(
                    haveObject,
                    CGGeneric(conversion),
                    CGGeneric("${declName} = nullptr;\n"),
                ).define()
            else:
                template = conversion
        else:
            template = wrapObjectTemplate(
                "if (JS::IsCallable(&${val}.toObject())) {\n"
                + conversion
                + "} else {\n"
                + indent(onFailureNotCallable(failureCode).define())
                + "}\n",
                type,
                "${declName} = nullptr;\n",
                failureCode,
            )
        return JSToNativeConversionInfo(
            template, declType=declType, declArgs=declArgs, dealWithOptional=isOptional
        )

    if type.isAny():
        assert not isEnforceRange and not isClamp and not isAllowShared

        declArgs = None
        if isMember in ("Variadic", "Sequence", "Dictionary", "Record"):
            # Rooting is handled by the sequence and dictionary tracers.
            declType = "JS::Value"
        else:
            assert not isMember
            declType = "JS::Rooted<JS::Value>"
            declArgs = "cx"

        assert not isOptional
        templateBody = "${declName} = ${val};\n"

        # For JS-implemented APIs, we refuse to allow passing objects that the
        # API consumer does not subsume. The extra parens around
        # ($${passedToJSImpl}) suppress unreachable code warnings when
        # $${passedToJSImpl} is the literal `false`.  But Apple is shipping a
        # buggy clang (clang 3.9) in Xcode 8.3, so there even the parens are not
        # enough.  So we manually disable some warnings in clang.
        if (
            not isinstance(descriptorProvider, Descriptor)
            or descriptorProvider.interface.isJSImplemented()
        ):
            templateBody = (
                fill(
                    """
                #ifdef __clang__
                #pragma clang diagnostic push
                #pragma clang diagnostic ignored "-Wunreachable-code"
                #pragma clang diagnostic ignored "-Wunreachable-code-return"
                #endif // __clang__
                if (($${passedToJSImpl}) && !CallerSubsumes($${val})) {
                  cx.ThrowErrorMessage<MSG_PERMISSION_DENIED_TO_PASS_ARG>("${sourceDescription}");
                  $*{exceptionCode}
                }
                #ifdef __clang__
                #pragma clang diagnostic pop
                #endif // __clang__
                """,
                    sourceDescription=sourceDescription,
                    exceptionCode=exceptionCode,
                )
                + templateBody
            )

        # We may not have a default value if we're being converted for
        # a setter, say.
        if defaultValue:
            if isinstance(defaultValue, IDLNullValue):
                defaultHandling = "${declName} = JS::NullValue();\n"
            else:
                assert isinstance(defaultValue, IDLUndefinedValue)
                defaultHandling = "${declName} = JS::UndefinedValue();\n"
            templateBody = handleDefault(templateBody, defaultHandling)
        return JSToNativeConversionInfo(
            templateBody, declType=CGGeneric(declType), declArgs=declArgs
        )

    if type.isObject():
        assert not isEnforceRange and not isClamp and not isAllowShared
        return handleJSObjectType(
            type, isMember, failureCode, exceptionCode, sourceDescription
        )

    if type.isDictionary():
        # There are no nullable dictionary-typed arguments or dictionary-typed
        # dictionary members.
        assert (
            not type.nullable()
            or isCallbackReturnValue
            or (isMember and isMember != "Dictionary")
        )
        # All optional dictionary-typed arguments always have default values,
        # but dictionary-typed dictionary members can be optional.
        assert not isOptional or isMember == "Dictionary"
        # In the callback return value case we never have to worry
        # about a default value; we always have a value.
        assert not isCallbackReturnValue or defaultValue is None

        typeName = CGDictionary.makeDictionaryName(type.unroll().inner)
        if (not isMember or isMember == "Union") and not isCallbackReturnValue:
            # Since we're not a member and not nullable or optional, no one will
            # see our real type, so we can do the fast version of the dictionary
            # that doesn't pre-initialize members.
            typeName = "binding_detail::Fast" + typeName

        declType = CGGeneric(typeName)

        # We do manual default value handling here, because we actually do want
        # a jsval, and we only handle the default-dictionary case (which we map
        # into initialization with the JS value `null`) anyway
        # NOTE: if isNullOrUndefined or isDefinitelyObject are true,
        # we know we have a value, so we don't have to worry about the
        # default value.
        if (
            not isNullOrUndefined
            and not isDefinitelyObject
            and defaultValue is not None
        ):
            assert isinstance(defaultValue, IDLDefaultDictionaryValue)
            # Initializing from JS null does the right thing to give
            # us a default-initialized dictionary.
            val = "(${haveValue}) ? ${val} : JS::NullHandleValue"
        else:
            val = "${val}"

        dictLoc = "${declName}"
        if type.nullable():
            dictLoc += ".SetValue()"

        if type.unroll().inner.needsConversionFromJS:
            args = "cx, %s, " % val
        else:
            # We can end up in this case if a dictionary that does not need
            # conversion from JS has a dictionary-typed member with a default
            # value of {}.
            args = ""
        conversionCode = fill(
            """
            if (!${dictLoc}.Init(${args}"${desc}", $${passedToJSImpl})) {
              $*{exceptionCode}
            }
            """,
            dictLoc=dictLoc,
            args=args,
            desc=firstCap(sourceDescription),
            exceptionCode=exceptionCode,
        )

        if failureCode is not None:
            # This means we're part of an overload or union conversion, and
            # should simply skip stuff if our value is not convertible to
            # dictionary, instead of trying and throwing.  If we're either
            # isDefinitelyObject or isNullOrUndefined then we're convertible to
            # dictionary and don't need to check here.
            if isDefinitelyObject or isNullOrUndefined:
                template = conversionCode
            else:
                template = fill(
                    """
                    if (!IsConvertibleToDictionary(${val})) {
                      $*{failureCode}
                    }
                    $*{conversionCode}
                    """,
                    val=val,
                    failureCode=failureCode,
                    conversionCode=conversionCode,
                )
        else:
            template = conversionCode

        if type.nullable():
            declType = CGTemplatedType("Nullable", declType)
            template = CGIfElseWrapper(
                "${val}.isNullOrUndefined()",
                CGGeneric("${declName}.SetNull();\n"),
                CGGeneric(template),
            ).define()

        # Dictionary arguments that might contain traceable things need to get
        # traced
        if (not isMember or isMember == "Union") and isCallbackReturnValue:
            # Go ahead and just convert directly into our actual return value
            declType = CGWrapper(declType, post="&")
            declArgs = "aRetVal"
        elif (not isMember or isMember == "Union") and typeNeedsRooting(type):
            declType = CGTemplatedType("RootedDictionary", declType)
            declArgs = "cx"
        else:
            declArgs = None

        return JSToNativeConversionInfo(
            template, declType=declType, declArgs=declArgs, dealWithOptional=isOptional
        )

    if type.isUndefined():
        assert not isOptional
        # This one only happens for return values, and its easy: Just
        # ignore the jsval.
        return JSToNativeConversionInfo("")

    if not type.isPrimitive():
        raise TypeError("Need conversion for argument type '%s'" % str(type))

    typeName = builtinNames[type.tag()]

    conversionBehavior = "eDefault"
    if isEnforceRange:
        assert type.isInteger()
        conversionBehavior = "eEnforceRange"
    elif isClamp:
        assert type.isInteger()
        conversionBehavior = "eClamp"

    alwaysNull = False
    if type.nullable():
        declType = CGGeneric("Nullable<" + typeName + ">")
        writeLoc = "${declName}.SetValue()"
        readLoc = "${declName}.Value()"
        nullCondition = "${val}.isNullOrUndefined()"
        if defaultValue is not None and isinstance(defaultValue, IDLNullValue):
            nullCondition = "!(${haveValue}) || " + nullCondition
            if isKnownMissing:
                alwaysNull = True
                template = dedent(
                    """
                    ${declName}.SetNull();
                    """
                )
        if not alwaysNull:
            template = fill(
                """
                if (${nullCondition}) {
                  $${declName}.SetNull();
                } else if (!ValueToPrimitive<${typeName}, ${conversionBehavior}>(cx, $${val}, "${sourceDescription}", &${writeLoc})) {
                  $*{exceptionCode}
                }
                """,
                nullCondition=nullCondition,
                typeName=typeName,
                conversionBehavior=conversionBehavior,
                sourceDescription=firstCap(sourceDescription),
                writeLoc=writeLoc,
                exceptionCode=exceptionCode,
            )
    else:
        assert defaultValue is None or not isinstance(defaultValue, IDLNullValue)
        writeLoc = "${declName}"
        readLoc = writeLoc
        template = fill(
            """
            if (!ValueToPrimitive<${typeName}, ${conversionBehavior}>(cx, $${val}, "${sourceDescription}", &${writeLoc})) {
              $*{exceptionCode}
            }
            """,
            typeName=typeName,
            conversionBehavior=conversionBehavior,
            sourceDescription=firstCap(sourceDescription),
            writeLoc=writeLoc,
            exceptionCode=exceptionCode,
        )
        declType = CGGeneric(typeName)

    if type.isFloat() and not type.isUnrestricted() and not alwaysNull:
        if lenientFloatCode is not None:
            nonFiniteCode = lenientFloatCode
        else:
            nonFiniteCode = 'cx.ThrowErrorMessage<MSG_NOT_FINITE>("%s");\n' "%s" % (
                firstCap(sourceDescription),
                exceptionCode,
            )

        # We're appending to an if-block brace, so strip trailing whitespace
        # and add an extra space before the else.
        template = template.rstrip()
        template += fill(
            """
             else if (!std::isfinite(${readLoc})) {
              $*{nonFiniteCode}
            }
            """,
            readLoc=readLoc,
            nonFiniteCode=nonFiniteCode,
        )

    if (
        defaultValue is not None
        and
        # We already handled IDLNullValue, so just deal with the other ones
        not isinstance(defaultValue, IDLNullValue)
    ):
        tag = defaultValue.type.tag()
        defaultStr = getHandleDefault(defaultValue)
        template = handleDefault(template, "%s = %s;\n" % (writeLoc, defaultStr))

    return JSToNativeConversionInfo(
        template, declType=declType, dealWithOptional=isOptional
    )


def instantiateJSToNativeConversion(info, replacements, checkForValue=False):
    """
    Take a JSToNativeConversionInfo as returned by getJSToNativeConversionInfo
    and a set of replacements as required by the strings in such an object, and
    generate code to convert into stack C++ types.

    If checkForValue is True, then the conversion will get wrapped in
    a check for ${haveValue}.
    """
    templateBody, declType, holderType, dealWithOptional = (
        info.template,
        info.declType,
        info.holderType,
        info.dealWithOptional,
    )

    if dealWithOptional and not checkForValue:
        raise TypeError("Have to deal with optional things, but don't know how")
    if checkForValue and declType is None:
        raise TypeError(
            "Need to predeclare optional things, so they will be "
            "outside the check for big enough arg count!"
        )

    # We can't precompute our holder constructor arguments, since
    # those might depend on ${declName}, which we change below.  Just
    # compute arguments at the point when we need them as we go.
    def getArgsCGThing(args):
        return CGGeneric(string.Template(args).substitute(replacements))

    result = CGList([])
    # Make a copy of "replacements" since we may be about to start modifying it
    replacements = dict(replacements)
    originalDeclName = replacements["declName"]
    if declType is not None:
        if dealWithOptional:
            replacements["declName"] = "%s.Value()" % originalDeclName
            declType = CGTemplatedType("Optional", declType)
            declCtorArgs = None
        elif info.declArgs is not None:
            declCtorArgs = CGWrapper(getArgsCGThing(info.declArgs), pre="(", post=")")
        else:
            declCtorArgs = None
        result.append(
            CGList(
                [
                    declType,
                    CGGeneric(" "),
                    CGGeneric(originalDeclName),
                    declCtorArgs,
                    CGGeneric(";\n"),
                ]
            )
        )

    originalHolderName = replacements["holderName"]
    if holderType is not None:
        if dealWithOptional:
            replacements["holderName"] = "%s.ref()" % originalHolderName
            holderType = CGTemplatedType("Maybe", holderType)
            holderCtorArgs = None
        elif info.holderArgs is not None:
            holderCtorArgs = CGWrapper(
                getArgsCGThing(info.holderArgs), pre="(", post=")"
            )
        else:
            holderCtorArgs = None
        result.append(
            CGList(
                [
                    holderType,
                    CGGeneric(" "),
                    CGGeneric(originalHolderName),
                    holderCtorArgs,
                    CGGeneric(";\n"),
                ]
            )
        )

    if "maybeMutableVal" not in replacements:
        replacements["maybeMutableVal"] = replacements["val"]

    conversion = CGGeneric(string.Template(templateBody).substitute(replacements))

    if checkForValue:
        if dealWithOptional:
            declConstruct = CGIndenter(
                CGGeneric(
                    "%s.Construct(%s);\n"
                    % (
                        originalDeclName,
                        getArgsCGThing(info.declArgs).define() if info.declArgs else "",
                    )
                )
            )
            if holderType is not None:
                holderConstruct = CGIndenter(
                    CGGeneric(
                        "%s.emplace(%s);\n"
                        % (
                            originalHolderName,
                            (
                                getArgsCGThing(info.holderArgs).define()
                                if info.holderArgs
                                else ""
                            ),
                        )
                    )
                )
            else:
                holderConstruct = None
        else:
            declConstruct = None
            holderConstruct = None

        conversion = CGList(
            [
                CGGeneric(
                    string.Template("if (${haveValue}) {\n").substitute(replacements)
                ),
                declConstruct,
                holderConstruct,
                CGIndenter(conversion),
                CGGeneric("}\n"),
            ]
        )

    result.append(conversion)
    return result


def convertConstIDLValueToJSVal(value):
    if isinstance(value, IDLNullValue):
        return "JS::NullValue()"
    if isinstance(value, IDLUndefinedValue):
        return "JS::UndefinedValue()"
    tag = value.type.tag()
    if tag in [
        IDLType.Tags.int8,
        IDLType.Tags.uint8,
        IDLType.Tags.int16,
        IDLType.Tags.uint16,
        IDLType.Tags.int32,
    ]:
        return "JS::Int32Value(%s)" % (value.value)
    if tag == IDLType.Tags.uint32:
        return "JS::NumberValue(%sU)" % (value.value)
    if tag in [IDLType.Tags.int64, IDLType.Tags.uint64]:
        return "JS::CanonicalizedDoubleValue(%s)" % numericValue(tag, value.value)
    if tag == IDLType.Tags.bool:
        return "JS::BooleanValue(%s)" % (toStringBool(value.value))
    if tag in [IDLType.Tags.float, IDLType.Tags.double]:
        return "JS::CanonicalizedDoubleValue(%s)" % (value.value)
    raise TypeError("Const value of unhandled type: %s" % value.type)


class CGArgumentConverter(CGThing):
    """
    A class that takes an IDL argument object and its index in the
    argument list and generates code to unwrap the argument to the
    right native type.

    argDescription is a description of the argument for error-reporting
    purposes.  Callers should assume that it might get placed in the middle of a
    sentence.  If it ends up at the beginning of a sentence, its first character
    will be automatically uppercased.
    """

    def __init__(
        self,
        argument,
        index,
        descriptorProvider,
        argDescription,
        member,
        invalidEnumValueFatal=True,
        lenientFloatCode=None,
    ):
        CGThing.__init__(self)
        self.argument = argument
        self.argDescription = argDescription
        assert not argument.defaultValue or argument.optional

        replacer = {"index": index, "argc": "args.length()"}
        self.replacementVariables = {
            "declName": "arg%d" % index,
            "holderName": ("arg%d" % index) + "_holder",
            "obj": "obj",
            "passedToJSImpl": toStringBool(
                isJSImplementedDescriptor(descriptorProvider)
            ),
        }
        # If we have a method generated by the maplike/setlike portion of an
        # interface, arguments can possibly be undefined, but will need to be
        # converted to the key/value type of the backing object. In this case,
        # use .get() instead of direct access to the argument. This won't
        # matter for iterable since generated functions for those interface
        # don't take arguments.
        if member.isMethod() and member.isMaplikeOrSetlikeOrIterableMethod():
            self.replacementVariables["val"] = string.Template(
                "args.get(${index})"
            ).substitute(replacer)
            self.replacementVariables["maybeMutableVal"] = string.Template(
                "args[${index}]"
            ).substitute(replacer)
        else:
            self.replacementVariables["val"] = string.Template(
                "args[${index}]"
            ).substitute(replacer)
        haveValueCheck = string.Template("args.hasDefined(${index})").substitute(
            replacer
        )
        self.replacementVariables["haveValue"] = haveValueCheck
        self.descriptorProvider = descriptorProvider
        if self.argument.canHaveMissingValue():
            self.argcAndIndex = replacer
        else:
            self.argcAndIndex = None
        self.invalidEnumValueFatal = invalidEnumValueFatal
        self.lenientFloatCode = lenientFloatCode

    def define(self):
        typeConversion = getJSToNativeConversionInfo(
            self.argument.type,
            self.descriptorProvider,
            isOptional=(self.argcAndIndex is not None and not self.argument.variadic),
            invalidEnumValueFatal=self.invalidEnumValueFatal,
            defaultValue=self.argument.defaultValue,
            lenientFloatCode=self.lenientFloatCode,
            isMember="Variadic" if self.argument.variadic else False,
            allowTreatNonCallableAsNull=self.argument.allowTreatNonCallableAsNull(),
            sourceDescription=self.argDescription,
        )

        if not self.argument.variadic:
            return instantiateJSToNativeConversion(
                typeConversion, self.replacementVariables, self.argcAndIndex is not None
            ).define()

        # Variadic arguments get turned into a sequence.
        if typeConversion.dealWithOptional:
            raise TypeError("Shouldn't have optional things in variadics")
        if typeConversion.holderType is not None:
            raise TypeError("Shouldn't need holders for variadics")

        replacer = dict(self.argcAndIndex, **self.replacementVariables)
        replacer["seqType"] = CGTemplatedType(
            "AutoSequence", typeConversion.declType
        ).define()
        if typeNeedsRooting(self.argument.type):
            rooterDecl = (
                "SequenceRooter<%s> ${holderName}(cx, &${declName});\n"
                % typeConversion.declType.define()
            )
        else:
            rooterDecl = ""
        replacer["elemType"] = typeConversion.declType.define()

        replacer["elementInitializer"] = initializerForType(self.argument.type) or ""

        # NOTE: Keep this in sync with sequence conversions as needed
        variadicConversion = string.Template(
            "${seqType} ${declName};\n"
            + rooterDecl
            + dedent(
                """
                if (${argc} > ${index}) {
                  if (!${declName}.SetCapacity(${argc} - ${index}, mozilla::fallible)) {
                    JS_ReportOutOfMemory(cx);
                    return false;
                  }
                  for (uint32_t variadicArg = ${index}; variadicArg < ${argc}; ++variadicArg) {
                    // OK to do infallible append here, since we ensured capacity already.
                    ${elemType}& slot = *${declName}.AppendElement(${elementInitializer});
                """
            )
        ).substitute(replacer)

        val = string.Template("args[variadicArg]").substitute(replacer)
        variadicConversion += indent(
            string.Template(typeConversion.template).substitute(
                {
                    "val": val,
                    "maybeMutableVal": val,
                    "declName": "slot",
                    # We only need holderName here to handle isExternal()
                    # interfaces, which use an internal holder for the
                    # conversion even when forceOwningType ends up true.
                    "holderName": "tempHolder",
                    # Use the same ${obj} as for the variadic arg itself
                    "obj": replacer["obj"],
                    "passedToJSImpl": toStringBool(
                        isJSImplementedDescriptor(self.descriptorProvider)
                    ),
                }
            ),
            4,
        )

        variadicConversion += "  }\n" "}\n"
        return variadicConversion


def getMaybeWrapValueFuncForType(type):
    if type.isJSString():
        return "MaybeWrapStringValue"
    # Callbacks might actually be DOM objects; nothing prevents a page from
    # doing that.
    if type.isCallback() or type.isCallbackInterface() or type.isObject():
        if type.nullable():
            return "MaybeWrapObjectOrNullValue"
        return "MaybeWrapObjectValue"
    # SpiderMonkey interfaces are never DOM objects.  Neither are sequences or
    # dictionaries, since those are always plain JS objects.
    if type.isSpiderMonkeyInterface() or type.isDictionary() or type.isSequence():
        if type.nullable():
            return "MaybeWrapNonDOMObjectOrNullValue"
        return "MaybeWrapNonDOMObjectValue"
    if type.isAny():
        return "MaybeWrapValue"

    # For other types, just go ahead an fall back on MaybeWrapValue for now:
    # it's always safe to do, and shouldn't be particularly slow for any of
    # them
    return "MaybeWrapValue"


sequenceWrapLevel = 0
recordWrapLevel = 0


def getWrapTemplateForType(
    type,
    descriptorProvider,
    result,
    successCode,
    returnsNewObject,
    exceptionCode,
    spiderMonkeyInterfacesAreStructs,
    isConstructorRetval=False,
):
    """
    Reflect a C++ value stored in "result", of IDL type "type" into JS.  The
    "successCode" is the code to run once we have successfully done the
    conversion and must guarantee that execution of the conversion template
    stops once the successCode has executed (e.g. by doing a 'return', or by
    doing a 'break' if the entire conversion template is inside a block that
    the 'break' will exit).

    If spiderMonkeyInterfacesAreStructs is true, then if the type is a
    SpiderMonkey interface, "result" is one of the
    dom::SpiderMonkeyInterfaceObjectStorage subclasses, not a JSObject*.

    The resulting string should be used with string.Template.  It
    needs the following keys when substituting:

      jsvalHandle: something that can be passed to methods taking a
                   JS::MutableHandle<JS::Value>.  This can be a
                   JS::MutableHandle<JS::Value> or a JS::Rooted<JS::Value>*.
      jsvalRef: something that can have .address() called on it to get a
                JS::Value* and .set() called on it to set it to a JS::Value.
                This can be a JS::MutableHandle<JS::Value> or a
                JS::Rooted<JS::Value>.
      obj: a JS::Handle<JSObject*>.

    Returns (templateString, infallibility of conversion template)
    """
    if successCode is None:
        successCode = "return true;\n"

    def setUndefined():
        return _setValue("", setter="setUndefined")

    def setNull():
        return _setValue("", setter="setNull")

    def setInt32(value):
        return _setValue(value, setter="setInt32")

    def setString(value):
        return _setValue(value, wrapAsType=type, setter="setString")

    def setObject(value, wrapAsType=None):
        return _setValue(value, wrapAsType=wrapAsType, setter="setObject")

    def setObjectOrNull(value, wrapAsType=None):
        return _setValue(value, wrapAsType=wrapAsType, setter="setObjectOrNull")

    def setUint32(value):
        return _setValue(value, setter="setNumber")

    def setDouble(value):
        return _setValue("JS_NumberValue(%s)" % value)

    def setBoolean(value):
        return _setValue(value, setter="setBoolean")

    def _setValue(value, wrapAsType=None, setter="set"):
        """
        Returns the code to set the jsval to value.

        If wrapAsType is not None, then will wrap the resulting value using the
        function that getMaybeWrapValueFuncForType(wrapAsType) returns.
        Otherwise, no wrapping will be done.
        """
        if wrapAsType is None:
            tail = successCode
        else:
            tail = fill(
                """
                if (!${maybeWrap}(cx, $${jsvalHandle})) {
                  $*{exceptionCode}
                }
                $*{successCode}
                """,
                maybeWrap=getMaybeWrapValueFuncForType(wrapAsType),
                exceptionCode=exceptionCode,
                successCode=successCode,
            )
        return ("${jsvalRef}.%s(%s);\n" % (setter, value)) + tail

    def wrapAndSetPtr(wrapCall, failureCode=None):
        """
        Returns the code to set the jsval by calling "wrapCall". "failureCode"
        is the code to run if calling "wrapCall" fails
        """
        if failureCode is None:
            failureCode = exceptionCode
        return fill(
            """
            if (!${wrapCall}) {
              $*{failureCode}
            }
            $*{successCode}
            """,
            wrapCall=wrapCall,
            failureCode=failureCode,
            successCode=successCode,
        )

    if type is None or type.isUndefined():
        return (setUndefined(), True)

    if (type.isSequence() or type.isRecord()) and type.nullable():
        # These are both wrapped in Nullable<>
        recTemplate, recInfall = getWrapTemplateForType(
            type.inner,
            descriptorProvider,
            "%s.Value()" % result,
            successCode,
            returnsNewObject,
            exceptionCode,
            spiderMonkeyInterfacesAreStructs,
        )
        code = fill(
            """

            if (${result}.IsNull()) {
              $*{setNull}
            }
            $*{recTemplate}
            """,
            result=result,
            setNull=setNull(),
            recTemplate=recTemplate,
        )
        return code, recInfall

    if type.isSequence():
        # Now do non-nullable sequences.  Our success code is just to break to
        # where we set the element in the array.  Note that we bump the
        # sequenceWrapLevel around this call so that nested sequence conversions
        # will use different iteration variables.
        global sequenceWrapLevel
        index = "sequenceIdx%d" % sequenceWrapLevel
        sequenceWrapLevel += 1
        innerTemplate = wrapForType(
            type.inner,
            descriptorProvider,
            {
                "result": "%s[%s]" % (result, index),
                "successCode": "break;\n",
                "jsvalRef": "tmp",
                "jsvalHandle": "&tmp",
                "returnsNewObject": returnsNewObject,
                "exceptionCode": exceptionCode,
                "obj": "returnArray",
                "spiderMonkeyInterfacesAreStructs": spiderMonkeyInterfacesAreStructs,
            },
        )
        sequenceWrapLevel -= 1
        code = fill(
            """

            uint32_t length = ${result}.Length();
            JS::Rooted<JSObject*> returnArray(cx, JS::NewArrayObject(cx, length));
            if (!returnArray) {
              $*{exceptionCode}
            }
            // Scope for 'tmp'
            {
              JS::Rooted<JS::Value> tmp(cx);
              for (uint32_t ${index} = 0; ${index} < length; ++${index}) {
                // Control block to let us common up the JS_DefineElement calls when there
                // are different ways to succeed at wrapping the object.
                do {
                  $*{innerTemplate}
                } while (false);
                if (!JS_DefineElement(cx, returnArray, ${index}, tmp,
                                      JSPROP_ENUMERATE)) {
                  $*{exceptionCode}
                }
              }
            }
            $*{set}
            """,
            result=result,
            exceptionCode=exceptionCode,
            index=index,
            innerTemplate=innerTemplate,
            set=setObject("*returnArray"),
        )

        return (code, False)

    if type.isRecord():
        # Now do non-nullable record.  Our success code is just to break to
        # where we define the property on the object.  Note that we bump the
        # recordWrapLevel around this call so that nested record conversions
        # will use different temp value names.
        global recordWrapLevel
        valueName = "recordValue%d" % recordWrapLevel
        recordWrapLevel += 1
        innerTemplate = wrapForType(
            type.inner,
            descriptorProvider,
            {
                "result": valueName,
                "successCode": "break;\n",
                "jsvalRef": "tmp",
                "jsvalHandle": "&tmp",
                "returnsNewObject": returnsNewObject,
                "exceptionCode": exceptionCode,
                "obj": "returnObj",
                "spiderMonkeyInterfacesAreStructs": spiderMonkeyInterfacesAreStructs,
            },
        )
        recordWrapLevel -= 1
        if type.keyType.isByteString():
            # There is no length-taking JS_DefineProperty.  So to keep
            # things sane with embedded nulls, we want to byte-inflate
            # to an nsAString.  The only byte-inflation function we
            # have around is AppendASCIItoUTF16, which luckily doesn't
            # assert anything about the input being ASCII.
            expandedKeyDecl = "NS_ConvertASCIItoUTF16 expandedKey(entry.mKey);\n"
            keyName = "expandedKey"
        elif type.keyType.isUTF8String():
            # We do the same as above for utf8 strings. We could do better if
            # we had a DefineProperty API that takes utf-8 property names.
            expandedKeyDecl = "NS_ConvertUTF8toUTF16 expandedKey(entry.mKey);\n"
            keyName = "expandedKey"
        else:
            expandedKeyDecl = ""
            keyName = "entry.mKey"

        code = fill(
            """

            JS::Rooted<JSObject*> returnObj(cx, JS_NewPlainObject(cx));
            if (!returnObj) {
              $*{exceptionCode}
            }
            // Scope for 'tmp'
            {
              JS::Rooted<JS::Value> tmp(cx);
              for (auto& entry : ${result}.Entries()) {
                auto& ${valueName} = entry.mValue;
                // Control block to let us common up the JS_DefineUCProperty calls when there
                // are different ways to succeed at wrapping the value.
                do {
                  $*{innerTemplate}
                } while (false);
                $*{expandedKeyDecl}
                if (!JS_DefineUCProperty(cx, returnObj,
                                         ${keyName}.BeginReading(),
                                         ${keyName}.Length(), tmp,
                                         JSPROP_ENUMERATE)) {
                  $*{exceptionCode}
                }
              }
            }
            $*{set}
            """,
            result=result,
            exceptionCode=exceptionCode,
            valueName=valueName,
            innerTemplate=innerTemplate,
            expandedKeyDecl=expandedKeyDecl,
            keyName=keyName,
            set=setObject("*returnObj"),
        )

        return (code, False)

    if type.isPromise():
        assert not type.nullable()
        # The use of ToJSValue here is a bit annoying because the Promise
        # version is not inlined.  But we can't put an inline version in either
        # ToJSValue.h or BindingUtils.h, because Promise.h includes ToJSValue.h
        # and that includes BindingUtils.h, so we'd get an include loop if
        # either of those headers included Promise.h.  And trying to write the
        # conversion by hand here is pretty annoying because we have to handle
        # the various RefPtr, rawptr, NonNull, etc cases, which ToJSValue will
        # handle for us.  So just eat the cost of the function call.
        return (wrapAndSetPtr("ToJSValue(cx, %s, ${jsvalHandle})" % result), False)

    if type.isGeckoInterface() and not type.isCallbackInterface():
        descriptor = descriptorProvider.getDescriptor(
            type.unroll().inner.identifier.name
        )
        if type.nullable():
            if descriptor.interface.identifier.name == "WindowProxy":
                template, infal = getWrapTemplateForType(
                    type.inner,
                    descriptorProvider,
                    "%s.Value()" % result,
                    successCode,
                    returnsNewObject,
                    exceptionCode,
                    spiderMonkeyInterfacesAreStructs,
                )
                return (
                    "if (%s.IsNull()) {\n" % result
                    + indent(setNull())
                    + "}\n"
                    + template,
                    infal,
                )

            wrappingCode = "if (!%s) {\n" % (result) + indent(setNull()) + "}\n"
        else:
            wrappingCode = ""

        if not descriptor.interface.isExternal():
            if descriptor.wrapperCache:
                wrapMethod = "GetOrCreateDOMReflector"
                wrapArgs = "cx, %s, ${jsvalHandle}" % result
            else:
                wrapMethod = "WrapNewBindingNonWrapperCachedObject"
                wrapArgs = "cx, ${obj}, %s, ${jsvalHandle}" % result
            if isConstructorRetval:
                wrapArgs += ", desiredProto"
            wrap = "%s(%s)" % (wrapMethod, wrapArgs)
            # Can only fail to wrap as a new-binding object if they already
            # threw an exception.
            failed = "MOZ_ASSERT(JS_IsExceptionPending(cx));\n" + exceptionCode
        else:
            if descriptor.notflattened:
                getIID = "&NS_GET_IID(%s), " % descriptor.nativeType
            else:
                getIID = ""
            wrap = "WrapObject(cx, %s, %s${jsvalHandle})" % (result, getIID)
            failed = None

        wrappingCode += wrapAndSetPtr(wrap, failed)
        return (wrappingCode, False)

    if type.isJSString():
        return (setString(result), False)

    if type.isDOMString() or type.isUSVString():
        if type.nullable():
            return (
                wrapAndSetPtr("xpc::StringToJsval(cx, %s, ${jsvalHandle})" % result),
                False,
            )
        else:
            return (
                wrapAndSetPtr(
                    "xpc::NonVoidStringToJsval(cx, %s, ${jsvalHandle})" % result
                ),
                False,
            )

    if type.isByteString():
        if type.nullable():
            return (
                wrapAndSetPtr("ByteStringToJsval(cx, %s, ${jsvalHandle})" % result),
                False,
            )
        else:
            return (
                wrapAndSetPtr(
                    "NonVoidByteStringToJsval(cx, %s, ${jsvalHandle})" % result
                ),
                False,
            )

    if type.isUTF8String():
        if type.nullable():
            return (
                wrapAndSetPtr("UTF8StringToJsval(cx, %s, ${jsvalHandle})" % result),
                False,
            )
        else:
            return (
                wrapAndSetPtr(
                    "NonVoidUTF8StringToJsval(cx, %s, ${jsvalHandle})" % result
                ),
                False,
            )

    if type.isEnum():
        if type.nullable():
            resultLoc = "%s.Value()" % result
        else:
            resultLoc = result
        conversion = fill(
            """
            if (!ToJSValue(cx, ${result}, $${jsvalHandle})) {
              $*{exceptionCode}
            }
            $*{successCode}
            """,
            result=resultLoc,
            exceptionCode=exceptionCode,
            successCode=successCode,
        )

        if type.nullable():
            conversion = CGIfElseWrapper(
                "%s.IsNull()" % result, CGGeneric(setNull()), CGGeneric(conversion)
            ).define()
        return conversion, False

    if type.isCallback() or type.isCallbackInterface():
        # Callbacks can store null if we nuked the compartments their
        # objects lived in.
        wrapCode = setObjectOrNull(
            "GetCallbackFromCallbackObject(cx, %(result)s)", wrapAsType=type
        )
        if type.nullable():
            wrapCode = (
                "if (%(result)s) {\n"
                + indent(wrapCode)
                + "} else {\n"
                + indent(setNull())
                + "}\n"
            )
        wrapCode = wrapCode % {"result": result}
        return wrapCode, False

    if type.isAny():
        # See comments in GetOrCreateDOMReflector explaining why we need
        # to wrap here.
        # NB: _setValue(..., type-that-is-any) calls JS_WrapValue(), so is fallible
        head = "JS::ExposeValueToActiveJS(%s);\n" % result
        return (head + _setValue(result, wrapAsType=type), False)

    if type.isObject() or (
        type.isSpiderMonkeyInterface() and not spiderMonkeyInterfacesAreStructs
    ):
        # See comments in GetOrCreateDOMReflector explaining why we need
        # to wrap here.
        if type.nullable():
            toValue = "%s"
            setter = setObjectOrNull
            head = """if (%s) {
              JS::ExposeObjectToActiveJS(%s);
            }
            """ % (
                result,
                result,
            )
        else:
            toValue = "*%s"
            setter = setObject
            head = "JS::ExposeObjectToActiveJS(%s);\n" % result
        # NB: setObject{,OrNull}(..., some-object-type) calls JS_WrapValue(), so is fallible
        return (head + setter(toValue % result, wrapAsType=type), False)

    if type.isObservableArray():
        # This first argument isn't used at all for now, the attribute getter
        # for ObservableArray type are generated in getObservableArrayGetterBody
        # instead.
        return "", False

    if not (
        type.isUnion()
        or type.isPrimitive()
        or type.isDictionary()
        or (type.isSpiderMonkeyInterface() and spiderMonkeyInterfacesAreStructs)
    ):
        raise TypeError("Need to learn to wrap %s" % type)

    if type.nullable():
        recTemplate, recInfal = getWrapTemplateForType(
            type.inner,
            descriptorProvider,
            "%s.Value()" % result,
            successCode,
            returnsNewObject,
            exceptionCode,
            spiderMonkeyInterfacesAreStructs,
        )
        return (
            "if (%s.IsNull()) {\n" % result + indent(setNull()) + "}\n" + recTemplate,
            recInfal,
        )

    if type.isSpiderMonkeyInterface():
        assert spiderMonkeyInterfacesAreStructs
        # See comments in GetOrCreateDOMReflector explaining why we need
        # to wrap here.
        # NB: setObject(..., some-object-type) calls JS_WrapValue(), so is fallible
        return (setObject("*%s.Obj()" % result, wrapAsType=type), False)

    if type.isUnion():
        return (wrapAndSetPtr("%s.ToJSVal(cx, ${obj}, ${jsvalHandle})" % result), False)

    if type.isDictionary():
        return (
            wrapAndSetPtr("%s.ToObjectInternal(cx, ${jsvalHandle})" % result),
            False,
        )

    tag = type.tag()

    if tag in [
        IDLType.Tags.int8,
        IDLType.Tags.uint8,
        IDLType.Tags.int16,
        IDLType.Tags.uint16,
        IDLType.Tags.int32,
    ]:
        return (setInt32("int32_t(%s)" % result), True)

    elif tag in [
        IDLType.Tags.int64,
        IDLType.Tags.uint64,
        IDLType.Tags.unrestricted_float,
        IDLType.Tags.float,
        IDLType.Tags.unrestricted_double,
        IDLType.Tags.double,
    ]:
        # XXXbz will cast to double do the "even significand" thing that webidl
        # calls for for 64-bit ints?  Do we care?
        return (setDouble("double(%s)" % result), True)

    elif tag == IDLType.Tags.uint32:
        return (setUint32(result), True)

    elif tag == IDLType.Tags.bool:
        return (setBoolean(result), True)

    else:
        raise TypeError("Need to learn to wrap primitive: %s" % type)


def wrapForType(type, descriptorProvider, templateValues):
    """
    Reflect a C++ value of IDL type "type" into JS.  TemplateValues is a dict
    that should contain:

      * 'jsvalRef': something that can have .address() called on it to get a
                    JS::Value* and .set() called on it to set it to a JS::Value.
                    This can be a JS::MutableHandle<JS::Value> or a
                    JS::Rooted<JS::Value>.
      * 'jsvalHandle': something that can be passed to methods taking a
                       JS::MutableHandle<JS::Value>.  This can be a
                       JS::MutableHandle<JS::Value> or a JS::Rooted<JS::Value>*.
      * 'obj' (optional): the name of the variable that contains the JSObject to
                          use as a scope when wrapping, if not supplied 'obj'
                          will be used as the name
      * 'result' (optional): the name of the variable in which the C++ value is
                             stored, if not supplied 'result' will be used as
                             the name
      * 'successCode' (optional): the code to run once we have successfully
                                  done the conversion, if not supplied 'return
                                  true;' will be used as the code.  The
                                  successCode must ensure that once it runs no
                                  more of the conversion template will be
                                  executed (e.g. by doing a 'return' or 'break'
                                  as appropriate).
      * 'returnsNewObject' (optional): If true, we're wrapping for the return
                                       value of a [NewObject] method.  Assumed
                                       false if not set.
      * 'exceptionCode' (optional): Code to run when a JS exception is thrown.
                                    The default is "return false;".  The code
                                    passed here must return.
      * 'isConstructorRetval' (optional): If true, we're wrapping a constructor
                                          return value.
    """
    wrap = getWrapTemplateForType(
        type,
        descriptorProvider,
        templateValues.get("result", "result"),
        templateValues.get("successCode", None),
        templateValues.get("returnsNewObject", False),
        templateValues.get("exceptionCode", "return false;\n"),
        templateValues.get("spiderMonkeyInterfacesAreStructs", False),
        isConstructorRetval=templateValues.get("isConstructorRetval", False),
    )[0]

    defaultValues = {"obj": "obj"}
    return string.Template(wrap).substitute(defaultValues, **templateValues)


def infallibleForMember(member, type, descriptorProvider):
    """
    Determine the fallibility of changing a C++ value of IDL type "type" into
    JS for the given attribute. Apart from returnsNewObject, all the defaults
    are used, since the fallbility does not change based on the boolean values,
    and the template will be discarded.

    CURRENT ASSUMPTIONS:
        We assume that successCode for wrapping up return values cannot contain
        failure conditions.
    """
    return getWrapTemplateForType(
        type,
        descriptorProvider,
        "result",
        None,
        memberReturnsNewObject(member),
        "return false;\n",
        False,
    )[1]


def leafTypeNeedsCx(type, retVal):
    return (
        type.isAny()
        or type.isObject()
        or type.isJSString()
        or (retVal and type.isSpiderMonkeyInterface())
    )


def leafTypeNeedsScopeObject(type, retVal):
    return retVal and type.isSpiderMonkeyInterface()


def leafTypeNeedsRooting(type):
    return leafTypeNeedsCx(type, False) or type.isSpiderMonkeyInterface()


def typeNeedsRooting(type):
    return typeMatchesLambda(type, lambda t: leafTypeNeedsRooting(t))


def typeNeedsCx(type, retVal=False):
    return typeMatchesLambda(type, lambda t: leafTypeNeedsCx(t, retVal))


def typeNeedsScopeObject(type, retVal=False):
    return typeMatchesLambda(type, lambda t: leafTypeNeedsScopeObject(t, retVal))


def typeMatchesLambda(type, func):
    if type is None:
        return False
    if type.nullable():
        return typeMatchesLambda(type.inner, func)
    if type.isSequence() or type.isRecord():
        return typeMatchesLambda(type.inner, func)
    if type.isUnion():
        return any(typeMatchesLambda(t, func) for t in type.unroll().flatMemberTypes)
    if type.isDictionary():
        return dictionaryMatchesLambda(type.inner, func)
    return func(type)


def dictionaryMatchesLambda(dictionary, func):
    return any(typeMatchesLambda(m.type, func) for m in dictionary.members) or (
        dictionary.parent and dictionaryMatchesLambda(dictionary.parent, func)
    )


# Whenever this is modified, please update CGNativeMember.getRetvalInfo as
# needed to keep the types compatible.
def getRetvalDeclarationForType(returnType, descriptorProvider, isMember=False):
    """
    Returns a tuple containing five things:

    1) A CGThing for the type of the return value, or None if there is no need
       for a return value.

    2) A value indicating the kind of ourparam to pass the value as.  Valid
       options are None to not pass as an out param at all, "ref" (to pass a
       reference as an out param), and "ptr" (to pass a pointer as an out
       param).

    3) A CGThing for a tracer for the return value, or None if no tracing is
       needed.

    4) An argument string to pass to the retval declaration
       constructor or None if there are no arguments.

    5) The name of a function that needs to be called with the return value
       before using it, or None if no function needs to be called.
    """
    if returnType is None or returnType.isUndefined():
        # Nothing to declare
        return None, None, None, None, None
    if returnType.isPrimitive() and returnType.tag() in builtinNames:
        result = CGGeneric(builtinNames[returnType.tag()])
        if returnType.nullable():
            result = CGTemplatedType("Nullable", result)
        return result, None, None, None, None
    if returnType.isJSString():
        if isMember:
            raise TypeError("JSString not supported as return type member")
        return CGGeneric("JS::Rooted<JSString*>"), "ptr", None, "cx", None
    if returnType.isDOMString() or returnType.isUSVString():
        if isMember:
            return CGGeneric("nsString"), "ref", None, None, None
        return CGGeneric("DOMString"), "ref", None, None, None
    if returnType.isByteString() or returnType.isUTF8String():
        if isMember:
            return CGGeneric("nsCString"), "ref", None, None, None
        return CGGeneric("nsAutoCString"), "ref", None, None, None
    if returnType.isEnum():
        result = CGGeneric(returnType.unroll().inner.identifier.name)
        if returnType.nullable():
            result = CGTemplatedType("Nullable", result)
        return result, None, None, None, None
    if returnType.isGeckoInterface() or returnType.isPromise():
        if returnType.isGeckoInterface():
            typeName = returnType.unroll().inner.identifier.name
            if typeName == "WindowProxy":
                result = CGGeneric("WindowProxyHolder")
                if returnType.nullable():
                    result = CGTemplatedType("Nullable", result)
                return result, None, None, None, None

            typeName = descriptorProvider.getDescriptor(typeName).nativeType
        else:
            typeName = "Promise"
        if isMember:
            conversion = None
            result = CGGeneric("StrongPtrForMember<%s>" % typeName)
        else:
            conversion = CGGeneric("StrongOrRawPtr<%s>" % typeName)
            result = CGGeneric("auto")
        return result, None, None, None, conversion
    if returnType.isCallback():
        name = returnType.unroll().callback.identifier.name
        return CGGeneric("RefPtr<%s>" % name), None, None, None, None
    if returnType.isAny():
        if isMember:
            return CGGeneric("JS::Value"), None, None, None, None
        return CGGeneric("JS::Rooted<JS::Value>"), "ptr", None, "cx", None
    if returnType.isObject() or returnType.isSpiderMonkeyInterface():
        if isMember:
            return CGGeneric("JSObject*"), None, None, None, None
        return CGGeneric("JS::Rooted<JSObject*>"), "ptr", None, "cx", None
    if returnType.isSequence():
        nullable = returnType.nullable()
        if nullable:
            returnType = returnType.inner
        result, _, _, _, _ = getRetvalDeclarationForType(
            returnType.inner, descriptorProvider, isMember="Sequence"
        )
        # While we have our inner type, set up our rooter, if needed
        if not isMember and typeNeedsRooting(returnType):
            rooter = CGGeneric(
                "SequenceRooter<%s > resultRooter(cx, &result);\n" % result.define()
            )
        else:
            rooter = None
        result = CGTemplatedType("nsTArray", result)
        if nullable:
            result = CGTemplatedType("Nullable", result)
        return result, "ref", rooter, None, None
    if returnType.isRecord():
        nullable = returnType.nullable()
        if nullable:
            returnType = returnType.inner
        result, _, _, _, _ = getRetvalDeclarationForType(
            returnType.inner, descriptorProvider, isMember="Record"
        )
        # While we have our inner type, set up our rooter, if needed
        if not isMember and typeNeedsRooting(returnType):
            rooter = CGGeneric(
                "RecordRooter<%s> resultRooter(cx, &result);\n"
                % ("nsString, " + result.define())
            )
        else:
            rooter = None
        result = CGTemplatedType("Record", [recordKeyDeclType(returnType), result])
        if nullable:
            result = CGTemplatedType("Nullable", result)
        return result, "ref", rooter, None, None
    if returnType.isDictionary():
        nullable = returnType.nullable()
        dictName = CGDictionary.makeDictionaryName(returnType.unroll().inner)
        result = CGGeneric(dictName)
        if not isMember and typeNeedsRooting(returnType):
            if nullable:
                result = CGTemplatedType("NullableRootedDictionary", result)
            else:
                result = CGTemplatedType("RootedDictionary", result)
            resultArgs = "cx"
        else:
            if nullable:
                result = CGTemplatedType("Nullable", result)
            resultArgs = None
        return result, "ref", None, resultArgs, None
    if returnType.isUnion():
        result = CGGeneric(CGUnionStruct.unionTypeName(returnType.unroll(), True))
        if not isMember and typeNeedsRooting(returnType):
            if returnType.nullable():
                result = CGTemplatedType("NullableRootedUnion", result)
            else:
                result = CGTemplatedType("RootedUnion", result)
            resultArgs = "cx"
        else:
            if returnType.nullable():
                result = CGTemplatedType("Nullable", result)
            resultArgs = None
        return result, "ref", None, resultArgs, None
    raise TypeError("Don't know how to declare return value for %s" % returnType)


def needCx(returnType, arguments, extendedAttributes, considerTypes, static=False):
    return (
        not static
        and considerTypes
        and (
            typeNeedsCx(returnType, True) or any(typeNeedsCx(a.type) for a in arguments)
        )
        or "implicitJSContext" in extendedAttributes
    )


def needScopeObject(
    returnType, arguments, extendedAttributes, isWrapperCached, considerTypes, isMember
):
    """
    isMember should be true if we're dealing with an attribute
    annotated as [StoreInSlot].
    """
    return (
        considerTypes
        and not isWrapperCached
        and (
            (not isMember and typeNeedsScopeObject(returnType, True))
            or any(typeNeedsScopeObject(a.type) for a in arguments)
        )
    )


def callerTypeGetterForDescriptor(descriptor):
    if descriptor.interface.isExposedInAnyWorker():
        systemCallerGetter = "nsContentUtils::ThreadsafeIsSystemCaller"
    else:
        systemCallerGetter = "nsContentUtils::IsSystemCaller"
    return "%s(cx) ? CallerType::System : CallerType::NonSystem" % systemCallerGetter


class CGCallGenerator(CGThing):
    """
    A class to generate an actual call to a C++ object.  Assumes that the C++
    object is stored in a variable whose name is given by the |object| argument.

    needsCallerType is a boolean indicating whether the call should receive
    a PrincipalType for the caller.

    needsErrorResult is a boolean indicating whether the call should be
    fallible and thus needs ErrorResult parameter.

    resultVar: If the returnType is not void, then the result of the call is
    stored in a C++ variable named by resultVar. The caller is responsible for
    declaring the result variable. If the caller doesn't care about the result
    value, resultVar can be omitted.

    context: The context string to pass to MaybeSetPendingException.
    """

    def __init__(
        self,
        needsErrorResult,
        needsCallerType,
        isChromeOnly,
        arguments,
        argsPre,
        returnType,
        extendedAttributes,
        descriptor,
        nativeMethodName,
        static,
        object="self",
        argsPost=[],
        resultVar=None,
        context="nullptr",
    ):
        CGThing.__init__(self)

        (
            result,
            resultOutParam,
            resultRooter,
            resultArgs,
            resultConversion,
        ) = getRetvalDeclarationForType(returnType, descriptor)

        args = CGList([CGGeneric(arg) for arg in argsPre], ", ")
        for a, name in arguments:
            arg = CGGeneric(name)

            # Now constify the things that need it
            def needsConst(a):
                if a.type.isDictionary():
                    return True
                if a.type.isSequence():
                    return True
                if a.type.isRecord():
                    return True
                # isObject() types are always a JS::Rooted, whether
                # nullable or not, and it turns out a const JS::Rooted
                # is not very helpful at all (in particular, it won't
                # even convert to a JS::Handle).
                # XXX bz Well, why not???
                if a.type.nullable() and not a.type.isObject():
                    return True
                if a.type.isString():
                    return True
                if a.canHaveMissingValue():
                    # This will need an Optional or it's a variadic;
                    # in both cases it should be const.
                    return True
                if a.type.isUnion():
                    return True
                if a.type.isSpiderMonkeyInterface():
                    return True
                return False

            if needsConst(a):
                arg = CGWrapper(arg, pre="Constify(", post=")")
            # And convert NonNull<T> to T&
            if (
                (a.type.isGeckoInterface() or a.type.isCallback() or a.type.isPromise())
                and not a.type.nullable()
            ) or a.type.isDOMString():
                arg = CGWrapper(arg, pre="NonNullHelper(", post=")")

            # If it's a refcounted object, let the static analysis know it's
            # alive for the duration of the call.
            if a.type.isGeckoInterface() or a.type.isCallback():
                arg = CGWrapper(arg, pre="MOZ_KnownLive(", post=")")

            args.append(arg)

        needResultDecl = False

        # Build up our actual call
        self.cgRoot = CGList([])

        # Return values that go in outparams go here
        if resultOutParam is not None:
            if resultVar is None:
                needResultDecl = True
                resultVar = "result"
            if resultOutParam == "ref":
                args.append(CGGeneric(resultVar))
            else:
                assert resultOutParam == "ptr"
                args.append(CGGeneric("&" + resultVar))

        needsSubjectPrincipal = "needsSubjectPrincipal" in extendedAttributes
        if needsSubjectPrincipal:
            needsNonSystemPrincipal = (
                "needsNonSystemSubjectPrincipal" in extendedAttributes
            )
            if needsNonSystemPrincipal:
                principalType = "nsIPrincipal*"
                subjectPrincipalArg = "subjectPrincipal"
                checkPrincipal = dedent(
                    """
                    if (principal->IsSystemPrincipal()) {
                      principal = nullptr;
                    }
                    """
                )
            else:
                principalType = "NonNull<nsIPrincipal>"
                subjectPrincipalArg = "NonNullHelper(subjectPrincipal)"
                checkPrincipal = ""

            self.cgRoot.append(
                CGGeneric(
                    fill(
                        """
                        ${principalType} subjectPrincipal;
                        {
                          JS::Realm* realm = js::GetContextRealm(cx);
                          MOZ_ASSERT(realm);
                          JSPrincipals* principals = JS::GetRealmPrincipals(realm);
                          nsIPrincipal* principal = nsJSPrincipals::get(principals);
                          ${checkPrincipal}
                          subjectPrincipal = principal;
                        }
                        """,
                        principalType=principalType,
                        checkPrincipal=checkPrincipal,
                    )
                )
            )

            args.append(CGGeneric("MOZ_KnownLive(%s)" % subjectPrincipalArg))

        if needsCallerType:
            if isChromeOnly:
                args.append(CGGeneric("SystemCallerGuarantee()"))
            else:
                args.append(CGGeneric(callerTypeGetterForDescriptor(descriptor)))

        canOOM = "canOOM" in extendedAttributes
        if needsErrorResult:
            args.append(CGGeneric("rv"))
        elif canOOM:
            args.append(CGGeneric("OOMReporter::From(rv)"))
        args.extend(CGGeneric(arg) for arg in argsPost)

        call = CGGeneric(nativeMethodName)
        if not static:
            call = CGWrapper(call, pre="%s->" % object)
        call = CGList([call, CGWrapper(args, pre="(", post=")")])
        if returnType is None or returnType.isUndefined() or resultOutParam is not None:
            assert resultConversion is None
            call = CGList(
                [
                    CGWrapper(
                        call,
                        pre=(
                            "// NOTE: This assert does NOT call the function.\n"
                            "static_assert(std::is_void_v<decltype("
                        ),
                        post=')>, "Should be returning void here");',
                    ),
                    call,
                ],
                "\n",
            )
        elif resultConversion is not None:
            call = CGList([resultConversion, CGWrapper(call, pre="(", post=")")])
        if resultVar is None and result is not None:
            needResultDecl = True
            resultVar = "result"

        if needResultDecl:
            if resultArgs is not None:
                resultArgsStr = "(%s)" % resultArgs
            else:
                resultArgsStr = ""
            result = CGWrapper(result, post=(" %s%s" % (resultVar, resultArgsStr)))
            if resultOutParam is None and resultArgs is None:
                call = CGList([result, CGWrapper(call, pre="(", post=")")])
            else:
                self.cgRoot.append(CGWrapper(result, post=";\n"))
                if resultOutParam is None:
                    call = CGWrapper(call, pre=resultVar + " = ")
            if resultRooter is not None:
                self.cgRoot.append(resultRooter)
        elif result is not None:
            assert resultOutParam is None
            call = CGWrapper(call, pre=resultVar + " = ")

        call = CGWrapper(call, post=";\n")
        self.cgRoot.append(call)

        if needsErrorResult or canOOM:
            self.cgRoot.prepend(CGGeneric("FastErrorResult rv;\n"))
            self.cgRoot.append(
                CGGeneric(
                    fill(
                        """
                if (MOZ_UNLIKELY(rv.MaybeSetPendingException(cx, ${context}))) {
                  return false;
                }
                """,
                        context=context,
                    )
                )
            )

        self.cgRoot.append(CGGeneric("MOZ_ASSERT(!JS_IsExceptionPending(cx));\n"))

    def define(self):
        return self.cgRoot.define()


def getUnionMemberName(type):
    # Promises can't be in unions, because they're not distinguishable
    # from anything else.
    assert not type.isPromise()
    if type.isGeckoInterface():
        return type.inner.identifier.name
    if type.isEnum():
        return type.inner.identifier.name
    return type.name


# A counter for making sure that when we're wrapping up things in
# nested sequences we don't use the same variable name to iterate over
# different sequences.
sequenceWrapLevel = 0
recordWrapLevel = 0


def wrapTypeIntoCurrentCompartment(type, value, isMember=True):
    """
    Take the thing named by "value" and if it contains "any",
    "object", or spidermonkey-interface types inside return a CGThing
    that will wrap them into the current compartment.
    """
    if type.isAny():
        assert not type.nullable()
        if isMember:
            value = "JS::MutableHandle<JS::Value>::fromMarkedLocation(&%s)" % value
        else:
            value = "&" + value
        return CGGeneric(
            "if (!JS_WrapValue(cx, %s)) {\n" "  return false;\n" "}\n" % value
        )

    if type.isObject():
        if isMember:
            value = "JS::MutableHandle<JSObject*>::fromMarkedLocation(&%s)" % value
        else:
            value = "&" + value
        return CGGeneric(
            "if (!JS_WrapObject(cx, %s)) {\n" "  return false;\n" "}\n" % value
        )

    if type.isSpiderMonkeyInterface():
        origValue = value
        if type.nullable():
            value = "%s.Value()" % value
        wrapCode = CGGeneric(
            "if (!%s.WrapIntoNewCompartment(cx)) {\n" "  return false;\n" "}\n" % value
        )
        if type.nullable():
            wrapCode = CGIfWrapper(wrapCode, "!%s.IsNull()" % origValue)
        return wrapCode

    if type.isSequence():
        origValue = value
        origType = type
        if type.nullable():
            type = type.inner
            value = "%s.Value()" % value
        global sequenceWrapLevel
        index = "indexName%d" % sequenceWrapLevel
        sequenceWrapLevel += 1
        wrapElement = wrapTypeIntoCurrentCompartment(
            type.inner, "%s[%s]" % (value, index)
        )
        sequenceWrapLevel -= 1
        if not wrapElement:
            return None
        wrapCode = CGWrapper(
            CGIndenter(wrapElement),
            pre=(
                "for (uint32_t %s = 0; %s < %s.Length(); ++%s) {\n"
                % (index, index, value, index)
            ),
            post="}\n",
        )
        if origType.nullable():
            wrapCode = CGIfWrapper(wrapCode, "!%s.IsNull()" % origValue)
        return wrapCode

    if type.isRecord():
        origType = type
        if type.nullable():
            type = type.inner
            recordRef = "%s.Value()" % value
        else:
            recordRef = value
        global recordWrapLevel
        entryRef = "mapEntry%d" % recordWrapLevel
        recordWrapLevel += 1
        wrapElement = wrapTypeIntoCurrentCompartment(type.inner, "%s.mValue" % entryRef)
        recordWrapLevel -= 1
        if not wrapElement:
            return None
        wrapCode = CGWrapper(
            CGIndenter(wrapElement),
            pre=("for (auto& %s : %s.Entries()) {\n" % (entryRef, recordRef)),
            post="}\n",
        )
        if origType.nullable():
            wrapCode = CGIfWrapper(wrapCode, "!%s.IsNull()" % value)
        return wrapCode

    if type.isDictionary():
        assert not type.nullable()
        myDict = type.inner
        memberWraps = []
        while myDict:
            for member in myDict.members:
                memberWrap = wrapArgIntoCurrentCompartment(
                    member,
                    "%s.%s"
                    % (value, CGDictionary.makeMemberName(member.identifier.name)),
                )
                if memberWrap:
                    memberWraps.append(memberWrap)
            myDict = myDict.parent
        return CGList(memberWraps) if len(memberWraps) != 0 else None

    if type.isUnion():
        origValue = value
        origType = type
        if type.nullable():
            type = type.inner
            value = "%s.Value()" % value
        memberWraps = []
        for member in type.flatMemberTypes:
            memberName = getUnionMemberName(member)
            memberWrap = wrapTypeIntoCurrentCompartment(
                member, "%s.GetAs%s()" % (value, memberName)
            )
            if memberWrap:
                memberWrap = CGIfWrapper(memberWrap, "%s.Is%s()" % (value, memberName))
                memberWraps.append(memberWrap)
        if len(memberWraps) == 0:
            return None
        wrapCode = CGList(memberWraps, "else ")
        if origType.nullable():
            wrapCode = CGIfWrapper(wrapCode, "!%s.IsNull()" % origValue)
        return wrapCode

    if (
        type.isUndefined()
        or type.isString()
        or type.isPrimitive()
        or type.isEnum()
        or type.isGeckoInterface()
        or type.isCallback()
        or type.isPromise()
    ):
        # All of these don't need wrapping.
        return None

    raise TypeError(
        "Unknown type; we don't know how to wrap it in constructor "
        "arguments: %s" % type
    )


def wrapArgIntoCurrentCompartment(arg, value, isMember=True):
    """
    As wrapTypeIntoCurrentCompartment but handles things being optional
    """
    origValue = value
    isOptional = arg.canHaveMissingValue()
    if isOptional:
        value = value + ".Value()"
    wrap = wrapTypeIntoCurrentCompartment(arg.type, value, isMember)
    if wrap and isOptional:
        wrap = CGIfWrapper(wrap, "%s.WasPassed()" % origValue)
    return wrap


def needsCallerType(m):
    return m.getExtendedAttribute("NeedsCallerType")


class CGPerSignatureCall(CGThing):
    """
    This class handles the guts of generating code for a particular
    call signature.  A call signature consists of four things:

    1) A return type, which can be None to indicate that there is no
       actual return value (e.g. this is an attribute setter) or an
       IDLType if there's an IDL type involved (including |void|).
    2) An argument list, which is allowed to be empty.
    3) A name of a native method to call. It is ignored for methods
       annotated with the "[WebExtensionStub=...]" extended attribute.
    4) Whether or not this method is static. Note that this only controls how
       the method is called (|self->nativeMethodName(...)| vs
       |nativeMethodName(...)|).

    We also need to know whether this is a method or a getter/setter
    to do error reporting correctly.

    The idlNode parameter can be either a method or an attr. We can query
    |idlNode.identifier| in both cases, so we can be agnostic between the two.

    dontSetSlot should be set to True if the value should not be cached in a
    slot (even if the attribute is marked as StoreInSlot or Cached in the
    WebIDL).

    errorReportingLabel can contain a custom label to use for error reporting.
    It will be inserted as is in the code, so if it needs to be a literal
    string in C++ it should be quoted.

    additionalArgsPre contains additional arguments that are added after the
    arguments that CGPerSignatureCall itself adds (JSContext, global, …), and
    before the actual arguments.
    """

    # XXXbz For now each entry in the argument list is either an
    # IDLArgument or a FakeArgument, but longer-term we may want to
    # have ways of flagging things like JSContext* or optional_argc in
    # there.

    def __init__(
        self,
        returnType,
        arguments,
        nativeMethodName,
        static,
        descriptor,
        idlNode,
        argConversionStartsAt=0,
        getter=False,
        setter=False,
        isConstructor=False,
        useCounterName=None,
        resultVar=None,
        objectName="obj",
        dontSetSlot=False,
        extendedAttributes=None,
        errorReportingLabel=None,
        additionalArgsPre=[],
    ):
        assert idlNode.isMethod() == (not getter and not setter)
        assert idlNode.isAttr() == (getter or setter)
        # Constructors are always static
        assert not isConstructor or static

        CGThing.__init__(self)
        self.returnType = returnType
        self.descriptor = descriptor
        self.idlNode = idlNode
        if extendedAttributes is None:
            extendedAttributes = descriptor.getExtendedAttributes(
                idlNode, getter=getter, setter=setter
            )
        self.extendedAttributes = extendedAttributes
        self.arguments = arguments
        self.argCount = len(arguments)
        self.isConstructor = isConstructor
        self.setSlot = (
            not dontSetSlot and idlNode.isAttr() and idlNode.slotIndices is not None
        )
        cgThings = []

        deprecated = idlNode.getExtendedAttribute("Deprecated") or (
            idlNode.isStatic()
            and descriptor.interface.getExtendedAttribute("Deprecated")
        )
        if deprecated:
            cgThings.append(
                CGGeneric(
                    dedent(
                        """
                DeprecationWarning(cx, obj, DeprecatedOperations::e%s);
                """
                        % deprecated[0]
                    )
                )
            )

        lenientFloatCode = None
        if idlNode.getExtendedAttribute("LenientFloat") is not None and (
            setter or idlNode.isMethod()
        ):
            cgThings.append(
                CGGeneric(
                    dedent(
                        """
                bool foundNonFiniteFloat = false;
                """
                    )
                )
            )
            lenientFloatCode = "foundNonFiniteFloat = true;\n"

        argsPre = []
        if idlNode.isStatic():
            # If we're a constructor, "obj" may not be a function, so calling
            # XrayAwareCalleeGlobal() on it is not safe.  Of course in the
            # constructor case either "obj" is an Xray or we're already in the
            # content compartment, not the Xray compartment, so just
            # constructing the GlobalObject from "obj" is fine.
            if isConstructor:
                objForGlobalObject = "obj"
            else:
                objForGlobalObject = "xpc::XrayAwareCalleeGlobal(obj)"
            cgThings.append(
                CGGeneric(
                    fill(
                        """
                GlobalObject global(cx, ${obj});
                if (global.Failed()) {
                  return false;
                }

                """,
                        obj=objForGlobalObject,
                    )
                )
            )
            argsPre.append("global")

        # For JS-implemented interfaces we do not want to base the
        # needsCx decision on the types involved, just on our extended
        # attributes. Also, JSContext is not needed for the static case
        # since GlobalObject already contains the context.
        needsCx = needCx(
            returnType,
            arguments,
            self.extendedAttributes,
            not descriptor.interface.isJSImplemented(),
            static,
        )
        if needsCx:
            argsPre.append("cx")

        needsUnwrap = False
        argsPost = []
        runConstructorInCallerCompartment = descriptor.interface.getExtendedAttribute(
            "RunConstructorInCallerCompartment"
        )
        if isConstructor and not runConstructorInCallerCompartment:
            needsUnwrap = True
            needsUnwrappedVar = False
            unwrappedVar = "obj"
            if descriptor.interface.isJSImplemented():
                # We need the desired proto in our constructor, because the
                # constructor will actually construct our reflector.
                argsPost.append("desiredProto")
        elif descriptor.interface.isJSImplemented():
            if not idlNode.isStatic():
                needsUnwrap = True
                needsUnwrappedVar = True
                argsPost.append(
                    "(unwrappedObj ? js::GetNonCCWObjectRealm(*unwrappedObj) : js::GetContextRealm(cx))"
                )
        elif needScopeObject(
            returnType,
            arguments,
            self.extendedAttributes,
            descriptor.wrapperCache,
            True,
            idlNode.getExtendedAttribute("StoreInSlot"),
        ):
            # If we ever end up with APIs like this on cross-origin objects,
            # figure out how the CheckedUnwrapDynamic bits should work.  Chances
            # are, just calling it with "cx" is fine...  For now, though, just
            # assert that it does not matter.
            assert not descriptor.isMaybeCrossOriginObject()
            # The scope object should always be from the relevant
            # global.  Make sure to unwrap it as needed.
            cgThings.append(
                CGGeneric(
                    dedent(
                        """
                JS::Rooted<JSObject*> unwrappedObj(cx, js::CheckedUnwrapStatic(obj));
                // Caller should have ensured that "obj" can be unwrapped already.
                MOZ_DIAGNOSTIC_ASSERT(unwrappedObj);
                """
                    )
                )
            )
            argsPre.append("unwrappedObj")

        if needsUnwrap and needsUnwrappedVar:
            # We cannot assign into obj because it's a Handle, not a
            # MutableHandle, so we need a separate Rooted.
            cgThings.append(CGGeneric("Maybe<JS::Rooted<JSObject*> > unwrappedObj;\n"))
            unwrappedVar = "unwrappedObj.ref()"

        if idlNode.isMethod() and idlNode.isLegacycaller():
            # If we can have legacycaller with identifier, we can't
            # just use the idlNode to determine whether we're
            # generating code for the legacycaller or not.
            assert idlNode.isIdentifierLess()
            # Pass in our thisVal
            argsPre.append("args.thisv()")

        if idlNode.isMethod():
            argDescription = "argument %(index)d"
        elif setter:
            argDescription = "value being assigned"
        else:
            assert self.argCount == 0

        if needsUnwrap:
            # It's very important that we construct our unwrappedObj, if we need
            # to do it, before we might start setting up Rooted things for our
            # arguments, so that we don't violate the stack discipline Rooted
            # depends on.
            cgThings.append(
                CGGeneric("bool objIsXray = xpc::WrapperFactory::IsXrayWrapper(obj);\n")
            )
            if needsUnwrappedVar:
                cgThings.append(
                    CGIfWrapper(
                        CGGeneric("unwrappedObj.emplace(cx, obj);\n"), "objIsXray"
                    )
                )

        for i in range(argConversionStartsAt, self.argCount):
            cgThings.append(
                CGArgumentConverter(
                    arguments[i],
                    i,
                    self.descriptor,
                    argDescription % {"index": i + 1},
                    idlNode,
                    invalidEnumValueFatal=not setter,
                    lenientFloatCode=lenientFloatCode,
                )
            )

        # Now that argument processing is done, enforce the LenientFloat stuff
        if lenientFloatCode:
            if setter:
                foundNonFiniteFloatBehavior = "return true;\n"
            else:
                assert idlNode.isMethod()
                foundNonFiniteFloatBehavior = dedent(
                    """
                    args.rval().setUndefined();
                    return true;
                    """
                )
            cgThings.append(
                CGGeneric(
                    fill(
                        """
                if (foundNonFiniteFloat) {
                  $*{returnSteps}
                }
                """,
                        returnSteps=foundNonFiniteFloatBehavior,
                    )
                )
            )

        if needsUnwrap:
            # Something depends on having the unwrapped object, so unwrap it now.
            xraySteps = []
            # XXXkhuey we should be able to MOZ_ASSERT that ${obj} is
            # not null.
            xraySteps.append(
                CGGeneric(
                    fill(
                        """
                    // Since our object is an Xray, we can just CheckedUnwrapStatic:
                    // we know Xrays have no dynamic unwrap behavior.
                    ${obj} = js::CheckedUnwrapStatic(${obj});
                    if (!${obj}) {
                      return false;
                    }
                    """,
                        obj=unwrappedVar,
                    )
                )
            )
            if isConstructor:
                # If we're called via an xray, we need to enter the underlying
                # object's compartment and then wrap up all of our arguments into
                # that compartment as needed.  This is all happening after we've
                # already done the conversions from JS values to WebIDL (C++)
                # values, so we only need to worry about cases where there are 'any'
                # or 'object' types, or other things that we represent as actual
                # JSAPI types, present.  Effectively, we're emulating a
                # CrossCompartmentWrapper, but working with the C++ types, not the
                # original list of JS::Values.
                cgThings.append(CGGeneric("Maybe<JSAutoRealm> ar;\n"))
                xraySteps.append(CGGeneric("ar.emplace(cx, obj);\n"))
                xraySteps.append(
                    CGGeneric(
                        dedent(
                            """
                    if (!JS_WrapObject(cx, &desiredProto)) {
                      return false;
                    }
                    """
                        )
                    )
                )
                xraySteps.extend(
                    wrapArgIntoCurrentCompartment(arg, argname, isMember=False)
                    for arg, argname in self.getArguments()
                )

            cgThings.append(CGIfWrapper(CGList(xraySteps), "objIsXray"))

        if idlNode.getExtendedAttribute("CEReactions") is not None and not getter:
            cgThings.append(
                CGGeneric(
                    dedent(
                        """
                Maybe<AutoCEReaction> ceReaction;
                DocGroup* docGroup = self->GetDocGroup();
                if (docGroup) {
                  ceReaction.emplace(docGroup->CustomElementReactionsStack(), cx);
                }
                """
                    )
                )
            )

        # If this is a method that was generated by a maplike/setlike
        # interface, use the maplike/setlike generator to fill in the body.
        # Otherwise, use CGCallGenerator to call the native method.
        if idlNode.isMethod() and idlNode.isMaplikeOrSetlikeOrIterableMethod():
            if (
                idlNode.maplikeOrSetlikeOrIterable.isMaplike()
                or idlNode.maplikeOrSetlikeOrIterable.isSetlike()
            ):
                cgThings.append(
                    CGMaplikeOrSetlikeMethodGenerator(
                        descriptor,
                        idlNode.maplikeOrSetlikeOrIterable,
                        idlNode.identifier.name,
                    )
                )
            else:
                cgThings.append(
                    CGIterableMethodGenerator(
                        descriptor,
                        idlNode.identifier.name,
                        self.getArgumentNames(),
                    )
                )
        elif idlNode.isAttr() and idlNode.type.isObservableArray():
            assert setter
            cgThings.append(CGObservableArraySetterGenerator(descriptor, idlNode))
        else:
            if errorReportingLabel is None:
                context = GetLabelForErrorReporting(descriptor, idlNode, isConstructor)
                if getter:
                    context = context + " getter"
                elif setter:
                    context = context + " setter"
                # Callee expects a quoted string for the context if
                # there's a context.
                context = '"%s"' % context
            else:
                context = errorReportingLabel

            if idlNode.isMethod() and idlNode.getExtendedAttribute("WebExtensionStub"):
                [
                    nativeMethodName,
                    argsPre,
                    args,
                ] = self.processWebExtensionStubAttribute(cgThings)
            else:
                args = self.getArguments()

            cgThings.append(
                CGCallGenerator(
                    self.needsErrorResult(),
                    needsCallerType(idlNode),
                    isChromeOnly(idlNode),
                    args,
                    argsPre + additionalArgsPre,
                    returnType,
                    self.extendedAttributes,
                    descriptor,
                    nativeMethodName,
                    static,
                    # We know our "self" must be being kept alive; otherwise we have
                    # a serious problem.  In common cases it's just an argument and
                    # we're MOZ_CAN_RUN_SCRIPT, but in some cases it's on the stack
                    # and being kept alive via references from JS.
                    object="MOZ_KnownLive(self)",
                    argsPost=argsPost,
                    resultVar=resultVar,
                    context=context,
                )
            )

        if useCounterName:
            # Generate a telemetry call for when [UseCounter] is used.
            windowCode = fill(
                """
                SetUseCounter(obj, eUseCounter_${useCounterName});
                """,
                useCounterName=useCounterName,
            )
            workerCode = fill(
                """
                SetUseCounter(UseCounterWorker::${useCounterName});
                """,
                useCounterName=useCounterName,
            )
            code = ""
            if idlNode.isExposedInWindow() and idlNode.isExposedInAnyWorker():
                code += fill(
                    """
                    if (NS_IsMainThread()) {
                      ${windowCode}
                    } else {
                      ${workerCode}
                    }
                    """,
                    windowCode=windowCode,
                    workerCode=workerCode,
                )
            elif idlNode.isExposedInWindow():
                code += windowCode
            elif idlNode.isExposedInAnyWorker():
                code += workerCode

            cgThings.append(CGGeneric(code))

        self.cgRoot = CGList(cgThings)

    def getArgumentNames(self):
        return ["arg" + str(i) for i in range(len(self.arguments))]

    def getArguments(self):
        return list(zip(self.arguments, self.getArgumentNames()))

    def processWebExtensionStubAttribute(self, cgThings):
        nativeMethodName = "CallWebExtMethod"
        stubNameSuffix = self.idlNode.getExtendedAttribute("WebExtensionStub")
        if isinstance(stubNameSuffix, list):
            nativeMethodName += stubNameSuffix[0]

        argsLength = len(self.getArguments())
        singleVariadicArg = argsLength == 1 and self.getArguments()[0][0].variadic

        # If the method signature does only include a single variadic arguments,
        # then `arg0` is already a Sequence of JS values and we can pass that
        # to the WebExtensions Stub method as is.
        if singleVariadicArg:
            argsPre = [
                "cx",
                'u"%s"_ns' % self.idlNode.identifier.name,
                "Constify(%s)" % "arg0",
            ]
            args = []
            return [nativeMethodName, argsPre, args]

        argsPre = [
            "cx",
            'u"%s"_ns' % self.idlNode.identifier.name,
            "Constify(%s)" % "args_sequence",
        ]
        args = []

        # Determine the maximum number of elements of the js values sequence argument,
        # skipping the last optional callback argument if any:
        #
        # if this WebExtensions API method does expect a last optional callback argument,
        # then it is the callback parameter supported for chrome-compatibility
        # reasons, and we want it as a separate argument passed to the WebExtension
        # stub method and skip it from the js values sequence including all other
        # arguments.
        maxArgsSequenceLen = argsLength
        if argsLength > 0:
            lastArg = self.getArguments()[argsLength - 1]
            isCallback = lastArg[0].type.tag() == IDLType.Tags.callback
            if isCallback and lastArg[0].optional:
                argsPre.append(
                    "MOZ_KnownLive(NonNullHelper(Constify(%s)))" % lastArg[1]
                )
                maxArgsSequenceLen = argsLength - 1

        cgThings.append(
            CGGeneric(
                dedent(
                    fill(
                        """
            // Collecting all args js values into the single sequence argument
            // passed to the webextensions stub method.
            //
            // NOTE: The stub method will receive the original non-normalized js values,
            // but those arguments will still be normalized on the main thread by the
            // WebExtensions API request handler using the same JSONSchema defnition
            // used by the non-webIDL webextensions API bindings.
            AutoSequence<JS::Value> args_sequence;
            SequenceRooter<JS::Value> args_sequence_holder(cx, &args_sequence);

            // maximum number of arguments expected by the WebExtensions API method
            // excluding the last optional chrome-compatible callback argument (which
            // is being passed to the stub method as a separate additional argument).
            uint32_t maxArgsSequenceLen = ${maxArgsSequenceLen};

            uint32_t sequenceArgsLen = args.length() <= maxArgsSequenceLen ?
              args.length() : maxArgsSequenceLen;

            if (sequenceArgsLen > 0) {
              if (!args_sequence.SetCapacity(sequenceArgsLen, mozilla::fallible)) {
                JS_ReportOutOfMemory(cx);
                return false;
              }
              for (uint32_t argIdx = 0; argIdx < sequenceArgsLen; ++argIdx) {
                // OK to do infallible append here, since we ensured capacity already.
                JS::Value& slot = *args_sequence.AppendElement();
                slot = args[argIdx];
              }
            }
            """,
                        maxArgsSequenceLen=maxArgsSequenceLen,
                    )
                )
            )
        )

        return [nativeMethodName, argsPre, args]

    def needsErrorResult(self):
        return "needsErrorResult" in self.extendedAttributes

    def wrap_return_value(self):
        wrapCode = ""

        returnsNewObject = memberReturnsNewObject(self.idlNode)
        if returnsNewObject and (
            self.returnType.isGeckoInterface() or self.returnType.isPromise()
        ):
            wrapCode += dedent(
                """
                static_assert(!std::is_pointer_v<decltype(result)>,
                              "NewObject implies that we need to keep the object alive with a strong reference.");
                """
            )

        if self.setSlot:
            # For attributes in slots, we want to do some
            # post-processing once we've wrapped them.
            successCode = "break;\n"
        else:
            successCode = None

        resultTemplateValues = {
            "jsvalRef": "args.rval()",
            "jsvalHandle": "args.rval()",
            "returnsNewObject": returnsNewObject,
            "isConstructorRetval": self.isConstructor,
            "successCode": successCode,
            # 'obj' in this dictionary is the thing whose compartment we are
            # trying to do the to-JS conversion in.  We're going to put that
            # thing in a variable named "conversionScope" if setSlot is true.
            # Otherwise, just use "obj" for lack of anything better.
            "obj": "conversionScope" if self.setSlot else "obj",
        }

        wrapCode += wrapForType(self.returnType, self.descriptor, resultTemplateValues)

        if self.setSlot:
            if self.idlNode.isStatic():
                raise TypeError(
                    "Attribute %s.%s is static, so we don't have a useful slot "
                    "to cache it in, because we don't have support for that on "
                    "interface objects.  See "
                    "https://bugzilla.mozilla.org/show_bug.cgi?id=1363870"
                    % (
                        self.descriptor.interface.identifier.name,
                        self.idlNode.identifier.name,
                    )
                )

            # When using a slot on the Xray expando, we need to make sure that
            # our initial conversion to a JS::Value is done in the caller
            # compartment.  When using a slot on our reflector, we want to do
            # the conversion in the compartment of that reflector (that is,
            # slotStorage).  In both cases we want to make sure that we finally
            # set up args.rval() to be in the caller compartment.  We also need
            # to make sure that the conversion steps happen inside a do/while
            # that they can break out of on success.
            #
            # Of course we always have to wrap the value into the slotStorage
            # compartment before we store it in slotStorage.

            # postConversionSteps are the steps that run while we're still in
            # the compartment we do our conversion in but after we've finished
            # the initial conversion into args.rval().
            postConversionSteps = ""
            if self.idlNode.getExtendedAttribute("Frozen"):
                assert (
                    self.idlNode.type.isSequence() or self.idlNode.type.isDictionary()
                )
                freezeValue = CGGeneric(
                    "JS::Rooted<JSObject*> rvalObj(cx, &args.rval().toObject());\n"
                    "if (!JS_FreezeObject(cx, rvalObj)) {\n"
                    "  return false;\n"
                    "}\n"
                )
                if self.idlNode.type.nullable():
                    freezeValue = CGIfWrapper(freezeValue, "args.rval().isObject()")
                postConversionSteps += freezeValue.define()

            # slotStorageSteps are steps that run once we have entered the
            # slotStorage compartment.
            if self.idlNode.getExtendedAttribute(
                "ReflectedHTMLAttributeReturningFrozenArray"
            ):
                storeInSlot = fill(
                    """
                    array[${arrayIndex}] = storedVal;
                    """,
                    arrayIndex=reflectedHTMLAttributesArrayIndex(
                        self.descriptor, self.idlNode
                    ),
                )
            else:
                storeInSlot = dedent(
                    """
                    JS::SetReservedSlot(slotStorage, slotIndex, storedVal);
                    """
                )

            slotStorageSteps = fill(
                """
                // Make a copy so that we don't do unnecessary wrapping on args.rval().
                JS::Rooted<JS::Value> storedVal(cx, args.rval());
                if (!${maybeWrap}(cx, &storedVal)) {
                  return false;
                }
                $*{storeInSlot}
                """,
                maybeWrap=getMaybeWrapValueFuncForType(self.idlNode.type),
                storeInSlot=storeInSlot,
            )

            checkForXray = mayUseXrayExpandoSlots(self.descriptor, self.idlNode)

            # For the case of Cached attributes, go ahead and preserve our
            # wrapper if needed.  We need to do this because otherwise the
            # wrapper could get garbage-collected and the cached value would
            # suddenly disappear, but the whole premise of cached values is that
            # they never change without explicit action on someone's part.  We
            # don't do this for StoreInSlot, since those get dealt with during
            # wrapper setup, and failure would involve us trying to clear an
            # already-preserved wrapper.
            if (
                self.idlNode.getExtendedAttribute("Cached")
                or self.idlNode.getExtendedAttribute(
                    "ReflectedHTMLAttributeReturningFrozenArray"
                )
            ) and self.descriptor.wrapperCache:
                preserveWrapper = dedent(
                    """
                    PreserveWrapper(self);
                    """
                )
                if checkForXray:
                    preserveWrapper = fill(
                        """
                        if (!isXray) {
                          // In the Xray case we don't need to do this, because getting the
                          // expando object already preserved our wrapper.
                          $*{preserveWrapper}
                        }
                        """,
                        preserveWrapper=preserveWrapper,
                    )
                slotStorageSteps += preserveWrapper

            if checkForXray:
                # In the Xray case we use the current global as conversion
                # scope, as explained in the big compartment/conversion comment
                # above.
                conversionScope = "isXray ? JS::CurrentGlobalOrNull(cx) : slotStorage"
            else:
                conversionScope = "slotStorage"

            wrapCode = fill(
                """
                {
                  JS::Rooted<JSObject*> conversionScope(cx, ${conversionScope});
                  JSAutoRealm ar(cx, conversionScope);
                  do { // block we break out of when done wrapping
                    $*{wrapCode}
                  } while (false);
                  $*{postConversionSteps}
                }
                { // And now store things in the realm of our slotStorage.
                  JSAutoRealm ar(cx, slotStorage);
                  $*{slotStorageSteps}
                }
                // And now make sure args.rval() is in the caller realm.
                return ${maybeWrap}(cx, args.rval());
                """,
                conversionScope=conversionScope,
                wrapCode=wrapCode,
                postConversionSteps=postConversionSteps,
                slotStorageSteps=slotStorageSteps,
                maybeWrap=getMaybeWrapValueFuncForType(self.idlNode.type),
            )
        return wrapCode

    def define(self):
        return self.cgRoot.define() + self.wrap_return_value()


class CGSwitch(CGList):
    """
    A class to generate code for a switch statement.

    Takes three constructor arguments: an expression, a list of cases,
    and an optional default.

    Each case is a CGCase.  The default is a CGThing for the body of
    the default case, if any.
    """

    def __init__(self, expression, cases, default=None):
        CGList.__init__(self, [CGIndenter(c) for c in cases])
        self.prepend(CGGeneric("switch (" + expression + ") {\n"))
        if default is not None:
            self.append(
                CGIndenter(
                    CGWrapper(CGIndenter(default), pre="default: {\n", post="}\n")
                )
            )

        self.append(CGGeneric("}\n"))


class CGCase(CGList):
    """
    A class to generate code for a case statement.

    Takes three constructor arguments: an expression, a CGThing for
    the body (allowed to be None if there is no body), and an optional
    argument for whether add a break, add fallthrough annotation or add nothing
    (defaulting to add a break).
    """

    ADD_BREAK = 0
    ADD_FALLTHROUGH = 1
    DONT_ADD_BREAK = 2

    def __init__(self, expression, body, breakOrFallthrough=ADD_BREAK):
        CGList.__init__(self, [])

        assert (
            breakOrFallthrough == CGCase.ADD_BREAK
            or breakOrFallthrough == CGCase.ADD_FALLTHROUGH
            or breakOrFallthrough == CGCase.DONT_ADD_BREAK
        )

        self.append(CGGeneric("case " + expression + ": {\n"))
        bodyList = CGList([body])
        if breakOrFallthrough == CGCase.ADD_FALLTHROUGH:
            bodyList.append(CGGeneric("[[fallthrough]];\n"))
        elif breakOrFallthrough == CGCase.ADD_BREAK:
            bodyList.append(CGGeneric("break;\n"))
        self.append(CGIndenter(bodyList))
        self.append(CGGeneric("}\n"))


class CGMethodCall(CGThing):
    """
    A class to generate selection of a method signature from a set of
    signatures and generation of a call to that signature.
    """

    def __init__(
        self, nativeMethodName, static, descriptor, method, isConstructor=False
    ):
        CGThing.__init__(self)

        methodName = GetLabelForErrorReporting(descriptor, method, isConstructor)
        argDesc = "argument %d"

        if method.getExtendedAttribute("UseCounter"):
            useCounterName = methodName.replace(".", "_").replace(" ", "_")
        else:
            useCounterName = None

        if method.isStatic():
            nativeType = descriptor.nativeType
            staticTypeOverride = PropertyDefiner.getStringAttr(
                method, "StaticClassOverride"
            )
            if staticTypeOverride:
                nativeType = staticTypeOverride
            nativeMethodName = "%s::%s" % (nativeType, nativeMethodName)

        def requiredArgCount(signature):
            arguments = signature[1]
            if len(arguments) == 0:
                return 0
            requiredArgs = len(arguments)
            while requiredArgs and arguments[requiredArgs - 1].optional:
                requiredArgs -= 1
            return requiredArgs

        def getPerSignatureCall(signature, argConversionStartsAt=0):
            return CGPerSignatureCall(
                signature[0],
                signature[1],
                nativeMethodName,
                static,
                descriptor,
                method,
                argConversionStartsAt=argConversionStartsAt,
                isConstructor=isConstructor,
                useCounterName=useCounterName,
            )

        signatures = method.signatures()
        if len(signatures) == 1:
            # Special case: we can just do a per-signature method call
            # here for our one signature and not worry about switching
            # on anything.
            signature = signatures[0]
            self.cgRoot = CGList([getPerSignatureCall(signature)])
            requiredArgs = requiredArgCount(signature)

            # Skip required arguments check for maplike/setlike interfaces, as
            # they can have arguments which are not passed, and are treated as
            # if undefined had been explicitly passed.
            if requiredArgs > 0 and not method.isMaplikeOrSetlikeOrIterableMethod():
                code = fill(
                    """
                    if (!args.requireAtLeast(cx, "${methodName}", ${requiredArgs})) {
                      return false;
                    }
                    """,
                    requiredArgs=requiredArgs,
                    methodName=methodName,
                )
                self.cgRoot.prepend(CGGeneric(code))
            return

        # Need to find the right overload
        maxArgCount = method.maxArgCount
        allowedArgCounts = method.allowedArgCounts

        argCountCases = []
        for argCountIdx, argCount in enumerate(allowedArgCounts):
            possibleSignatures = method.signaturesForArgCount(argCount)

            # Try to optimize away cases when the next argCount in the list
            # will have the same code as us; if it does, we can fall through to
            # that case.
            if argCountIdx + 1 < len(allowedArgCounts):
                nextPossibleSignatures = method.signaturesForArgCount(
                    allowedArgCounts[argCountIdx + 1]
                )
            else:
                nextPossibleSignatures = None
            if possibleSignatures == nextPossibleSignatures:
                # Same set of signatures means we better have the same
                # distinguishing index.  So we can in fact just fall through to
                # the next case here.
                assert len(possibleSignatures) == 1 or (
                    method.distinguishingIndexForArgCount(argCount)
                    == method.distinguishingIndexForArgCount(
                        allowedArgCounts[argCountIdx + 1]
                    )
                )
                argCountCases.append(
                    CGCase(str(argCount), None, CGCase.ADD_FALLTHROUGH)
                )
                continue

            if len(possibleSignatures) == 1:
                # easy case!
                signature = possibleSignatures[0]
                argCountCases.append(
                    CGCase(str(argCount), getPerSignatureCall(signature))
                )
                continue

            distinguishingIndex = method.distinguishingIndexForArgCount(argCount)

            def distinguishingArgument(signature):
                args = signature[1]
                if distinguishingIndex < len(args):
                    return args[distinguishingIndex]
                assert args[-1].variadic
                return args[-1]

            def distinguishingType(signature):
                return distinguishingArgument(signature).type

            for sig in possibleSignatures:
                # We should not have "any" args at distinguishingIndex,
                # since we have multiple possible signatures remaining,
                # but "any" is never distinguishable from anything else.
                assert not distinguishingType(sig).isAny()
                # We can't handle unions at the distinguishing index.
                if distinguishingType(sig).isUnion():
                    raise TypeError(
                        "No support for unions as distinguishing "
                        "arguments yet: %s" % distinguishingArgument(sig).location
                    )
                # We don't support variadics as the distinguishingArgument yet.
                # If you want to add support, consider this case:
                #
                #   undefined(long... foo);
                #   undefined(long bar, Int32Array baz);
                #
                # in which we have to convert argument 0 to long before picking
                # an overload... but all the variadic stuff needs to go into a
                # single array in case we pick that overload, so we have to have
                # machinery for converting argument 0 to long and then either
                # placing it in the variadic bit or not.  Or something.  We may
                # be able to loosen this restriction if the variadic arg is in
                # fact at distinguishingIndex, perhaps.  Would need to
                # double-check.
                if distinguishingArgument(sig).variadic:
                    raise TypeError(
                        "No support for variadics as distinguishing "
                        "arguments yet: %s" % distinguishingArgument(sig).location
                    )

            # Convert all our arguments up to the distinguishing index.
            # Doesn't matter which of the possible signatures we use, since
            # they all have the same types up to that point; just use
            # possibleSignatures[0]
            caseBody = [
                CGArgumentConverter(
                    possibleSignatures[0][1][i],
                    i,
                    descriptor,
                    argDesc % (i + 1),
                    method,
                )
                for i in range(0, distinguishingIndex)
            ]

            # Select the right overload from our set.
            distinguishingArg = "args[%d]" % distinguishingIndex

            def tryCall(
                signature, indent, isDefinitelyObject=False, isNullOrUndefined=False
            ):
                assert not isDefinitelyObject or not isNullOrUndefined
                assert isDefinitelyObject or isNullOrUndefined
                if isDefinitelyObject:
                    failureCode = "break;\n"
                else:
                    failureCode = None
                type = distinguishingType(signature)
                # The argument at index distinguishingIndex can't possibly be
                # unset here, because we've already checked that argc is large
                # enough that we can examine this argument.  But note that we
                # still want to claim that optional arguments are optional, in
                # case undefined was passed in.
                argIsOptional = distinguishingArgument(signature).canHaveMissingValue()
                testCode = instantiateJSToNativeConversion(
                    getJSToNativeConversionInfo(
                        type,
                        descriptor,
                        failureCode=failureCode,
                        isDefinitelyObject=isDefinitelyObject,
                        isNullOrUndefined=isNullOrUndefined,
                        isOptional=argIsOptional,
                        sourceDescription=(argDesc % (distinguishingIndex + 1)),
                    ),
                    {
                        "declName": "arg%d" % distinguishingIndex,
                        "holderName": ("arg%d" % distinguishingIndex) + "_holder",
                        "val": distinguishingArg,
                        "obj": "obj",
                        "haveValue": "args.hasDefined(%d)" % distinguishingIndex,
                        "passedToJSImpl": toStringBool(
                            isJSImplementedDescriptor(descriptor)
                        ),
                    },
                    checkForValue=argIsOptional,
                )
                caseBody.append(CGIndenter(testCode, indent))

                # If we got this far, we know we unwrapped to the right
                # C++ type, so just do the call.  Start conversion with
                # distinguishingIndex + 1, since we already converted
                # distinguishingIndex.
                caseBody.append(
                    CGIndenter(
                        getPerSignatureCall(signature, distinguishingIndex + 1), indent
                    )
                )

            def hasConditionalConversion(type):
                """
                Return whether the argument conversion for this type will be
                conditional on the type of incoming JS value.  For example, for
                interface types the conversion is conditional on the incoming
                value being isObject().

                For the types for which this returns false, we do not have to
                output extra isUndefined() or isNullOrUndefined() cases, because
                null/undefined values will just fall through into our
                unconditional conversion.
                """
                if type.isString() or type.isEnum():
                    return False
                if type.isBoolean():
                    distinguishingTypes = (
                        distinguishingType(s) for s in possibleSignatures
                    )
                    return any(
                        t.isString() or t.isEnum() or t.isNumeric()
                        for t in distinguishingTypes
                    )
                if type.isNumeric():
                    distinguishingTypes = (
                        distinguishingType(s) for s in possibleSignatures
                    )
                    return any(t.isString() or t.isEnum() for t in distinguishingTypes)
                return True

            def needsNullOrUndefinedCase(type):
                """
                Return true if the type needs a special isNullOrUndefined() case
                """
                return (
                    type.nullable() and hasConditionalConversion(type)
                ) or type.isDictionary()

            # First check for undefined and optional distinguishing arguments
            # and output a special branch for that case.  Note that we don't
            # use distinguishingArgument here because we actualy want to
            # exclude variadic arguments.  Also note that we skip this check if
            # we plan to output a isNullOrUndefined() special case for this
            # argument anyway, since that will subsume our isUndefined() check.
            # This is safe, because there can be at most one nullable
            # distinguishing argument, so if we're it we'll definitely get
            # picked up by the nullable handling.  Also, we can skip this check
            # if the argument has an unconditional conversion later on.
            undefSigs = [
                s
                for s in possibleSignatures
                if distinguishingIndex < len(s[1])
                and s[1][distinguishingIndex].optional
                and hasConditionalConversion(s[1][distinguishingIndex].type)
                and not needsNullOrUndefinedCase(s[1][distinguishingIndex].type)
            ]
            # Can't have multiple signatures with an optional argument at the
            # same index.
            assert len(undefSigs) < 2
            if len(undefSigs) > 0:
                caseBody.append(
                    CGGeneric("if (%s.isUndefined()) {\n" % distinguishingArg)
                )
                tryCall(undefSigs[0], 2, isNullOrUndefined=True)
                caseBody.append(CGGeneric("}\n"))

            # Next, check for null or undefined.  That means looking for
            # nullable arguments at the distinguishing index and outputting a
            # separate branch for them.  But if the nullable argument has an
            # unconditional conversion, we don't need to do that.  The reason
            # for that is that at most one argument at the distinguishing index
            # is nullable (since two nullable arguments are not
            # distinguishable), and null/undefined values will always fall
            # through to the unconditional conversion we have, if any, since
            # they will fail whatever the conditions on the input value are for
            # our other conversions.
            nullOrUndefSigs = [
                s
                for s in possibleSignatures
                if needsNullOrUndefinedCase(distinguishingType(s))
            ]
            # Can't have multiple nullable types here
            assert len(nullOrUndefSigs) < 2
            if len(nullOrUndefSigs) > 0:
                caseBody.append(
                    CGGeneric("if (%s.isNullOrUndefined()) {\n" % distinguishingArg)
                )
                tryCall(nullOrUndefSigs[0], 2, isNullOrUndefined=True)
                caseBody.append(CGGeneric("}\n"))

            # Now check for distinguishingArg being various kinds of objects.
            # The spec says to check for the following things in order:
            # 1)  A platform object that's not a platform array object, being
            #     passed to an interface or "object" arg.
            # 2)  A callable object being passed to a callback or "object" arg.
            # 3)  An iterable object being passed to a sequence arg.
            # 4)  Any object being passed to a array or callback interface or
            #     dictionary or "object" arg.

            # First grab all the overloads that have a non-callback interface
            # (which includes SpiderMonkey interfaces) at the distinguishing
            # index.  We can also include the ones that have an "object" here,
            # since if those are present no other object-typed argument will
            # be.
            objectSigs = [
                s
                for s in possibleSignatures
                if (
                    distinguishingType(s).isObject()
                    or distinguishingType(s).isNonCallbackInterface()
                )
            ]

            # And all the overloads that take callbacks
            objectSigs.extend(
                s for s in possibleSignatures if distinguishingType(s).isCallback()
            )

            # And all the overloads that take sequences
            objectSigs.extend(
                s for s in possibleSignatures if distinguishingType(s).isSequence()
            )

            # Now append all the overloads that take a dictionary or callback
            # interface or record.  There should be only one of these!
            genericObjectSigs = [
                s
                for s in possibleSignatures
                if (
                    distinguishingType(s).isDictionary()
                    or distinguishingType(s).isRecord()
                    or distinguishingType(s).isCallbackInterface()
                )
            ]
            assert len(genericObjectSigs) <= 1
            objectSigs.extend(genericObjectSigs)

            # There might be more than one thing in objectSigs; we need to check
            # which ones we unwrap to.
            if len(objectSigs) > 0:
                # Here it's enough to guard on our argument being an object.
                # The code for unwrapping non-callback interfaces, spiderMonkey
                # interfaces, and sequences will just bail out and move
                # on to the next overload if the object fails to unwrap
                # correctly, while "object" accepts any object anyway.  We
                # could even not do the isObject() check up front here, but in
                # cases where we have multiple object overloads it makes sense
                # to do it only once instead of for each overload.  That will
                # also allow the unwrapping test to skip having to do codegen
                # for the null-or-undefined case, which we already handled
                # above.
                caseBody.append(CGGeneric("if (%s.isObject()) {\n" % distinguishingArg))
                for sig in objectSigs:
                    caseBody.append(CGIndenter(CGGeneric("do {\n")))
                    # Indent by 4, since we need to indent further
                    # than our "do" statement
                    tryCall(sig, 4, isDefinitelyObject=True)
                    caseBody.append(CGIndenter(CGGeneric("} while (false);\n")))

                caseBody.append(CGGeneric("}\n"))

            # Now we only have to consider booleans, numerics, and strings.  If
            # we only have one of them, then we can just output it.  But if not,
            # then we need to output some of the cases conditionally: if we have
            # a string overload, then boolean and numeric are conditional, and
            # if not then boolean is conditional if we have a numeric overload.
            def findUniqueSignature(filterLambda):
                sigs = [s for s in possibleSignatures if filterLambda(s)]
                assert len(sigs) < 2
                if len(sigs) > 0:
                    return sigs[0]
                return None

            stringSignature = findUniqueSignature(
                lambda s: (
                    distinguishingType(s).isString() or distinguishingType(s).isEnum()
                )
            )
            numericSignature = findUniqueSignature(
                lambda s: distinguishingType(s).isNumeric()
            )
            booleanSignature = findUniqueSignature(
                lambda s: distinguishingType(s).isBoolean()
            )

            if stringSignature or numericSignature:
                booleanCondition = "%s.isBoolean()"
            else:
                booleanCondition = None

            if stringSignature:
                numericCondition = "%s.isNumber()"
            else:
                numericCondition = None

            def addCase(sig, condition):
                sigCode = getPerSignatureCall(sig, distinguishingIndex)
                if condition:
                    sigCode = CGIfWrapper(sigCode, condition % distinguishingArg)
                caseBody.append(sigCode)

            if booleanSignature:
                addCase(booleanSignature, booleanCondition)
            if numericSignature:
                addCase(numericSignature, numericCondition)
            if stringSignature:
                addCase(stringSignature, None)

            if not booleanSignature and not numericSignature and not stringSignature:
                # Just throw; we have no idea what we're supposed to
                # do with this.
                caseBody.append(
                    CGGeneric(
                        'return cx.ThrowErrorMessage<MSG_OVERLOAD_RESOLUTION_FAILED>("%d", "%d");\n'
                        % (distinguishingIndex + 1, argCount)
                    )
                )

            argCountCases.append(CGCase(str(argCount), CGList(caseBody)))

        overloadCGThings = []
        overloadCGThings.append(
            CGGeneric(
                "unsigned argcount = std::min(args.length(), %du);\n" % maxArgCount
            )
        )
        overloadCGThings.append(
            CGSwitch(
                "argcount",
                argCountCases,
                CGGeneric(
                    dedent(
                        """
                         // Using nsPrintfCString here would require including that
                         // header.  Let's not worry about it.
                         nsAutoCString argCountStr;
                         argCountStr.AppendPrintf("%u", args.length());
                         return cx.ThrowErrorMessage<MSG_INVALID_OVERLOAD_ARGCOUNT>(argCountStr.get());
                         """
                    )
                ),
            )
        )
        overloadCGThings.append(
            CGGeneric(
                'MOZ_CRASH("We have an always-returning default case");\n'
                "return false;\n"
            )
        )
        self.cgRoot = CGList(overloadCGThings)

    def define(self):
        return self.cgRoot.define()


class CGGetterCall(CGPerSignatureCall):
    """
    A class to generate a native object getter call for a particular IDL
    getter.
    """

    def __init__(
        self,
        returnType,
        nativeMethodName,
        descriptor,
        attr,
        errorReportingLabel=None,
        argsPre=[],
        dontSetSlot=False,
        extendedAttributes=None,
        preConversionCode=None,
    ):
        self.preConversionCode = preConversionCode
        if attr.getExtendedAttribute("UseCounter"):
            useCounterName = "%s_%s_getter" % (
                descriptor.interface.identifier.name,
                attr.identifier.name,
            )
        else:
            useCounterName = None
        if attr.isStatic():
            nativeMethodName = "%s::%s" % (descriptor.nativeType, nativeMethodName)
        CGPerSignatureCall.__init__(
            self,
            returnType,
            [],
            nativeMethodName,
            attr.isStatic(),
            descriptor,
            attr,
            getter=True,
            useCounterName=useCounterName,
            dontSetSlot=dontSetSlot,
            extendedAttributes=extendedAttributes,
            errorReportingLabel=errorReportingLabel,
            additionalArgsPre=argsPre,
        )

    def wrap_return_value(self):
        wrap = CGPerSignatureCall.wrap_return_value(self)
        if self.preConversionCode is not None:
            wrap = self.preConversionCode + wrap
        return wrap


class FakeIdentifier:
    def __init__(self, name):
        self.name = name


class FakeArgument:
    """
    A class that quacks like an IDLArgument.  This is used to make
    setters look like method calls or for special operations.
    """

    def __init__(self, type, name="arg", allowTreatNonCallableAsNull=False):
        self.type = type
        self.optional = False
        self.variadic = False
        self.defaultValue = None
        self._allowTreatNonCallableAsNull = allowTreatNonCallableAsNull

        self.identifier = FakeIdentifier(name)

    def allowTreatNonCallableAsNull(self):
        return self._allowTreatNonCallableAsNull

    def canHaveMissingValue(self):
        return False


class CGSetterCall(CGPerSignatureCall):
    """
    A class to generate a native object setter call for a particular IDL
    setter.
    """

    def __init__(
        self,
        argType,
        nativeMethodName,
        descriptor,
        attr,
        errorReportingLabel=None,
        argsPre=[],
    ):
        if attr.getExtendedAttribute("UseCounter"):
            useCounterName = "%s_%s_setter" % (
                descriptor.interface.identifier.name,
                attr.identifier.name,
            )
        else:
            useCounterName = None
        if attr.isStatic():
            nativeMethodName = "%s::%s" % (descriptor.nativeType, nativeMethodName)
        CGPerSignatureCall.__init__(
            self,
            None,
            [FakeArgument(argType, allowTreatNonCallableAsNull=True)],
            nativeMethodName,
            attr.isStatic(),
            descriptor,
            attr,
            setter=True,
            useCounterName=useCounterName,
            errorReportingLabel=errorReportingLabel,
            additionalArgsPre=argsPre,
        )

    def wrap_return_value(self):
        attr = self.idlNode
        clearSlot = ""
        if self.descriptor.wrapperCache and attr.slotIndices is not None:
            if attr.getExtendedAttribute("StoreInSlot"):
                clearSlot = "%s(cx, self);\n" % MakeClearCachedValueNativeName(
                    self.idlNode
                )
            elif attr.getExtendedAttribute("Cached"):
                clearSlot = "%s(self);\n" % MakeClearCachedValueNativeName(self.idlNode)

        # We have no return value
        return "\n" "%s" "return true;\n" % clearSlot


class CGAbstractBindingMethod(CGAbstractStaticMethod):
    """
    Common class to generate some of our class hooks.  This will generate the
    function declaration, get a reference to the JS object for our binding
    object (which might be an argument of the class hook or something we get
    from a JS::CallArgs), and unwrap into the right C++ type. Subclasses are
    expected to override the generate_code function to do the rest of the work.
    This function should return a CGThing which is already properly indented.

    getThisObj should be code for getting a JSObject* for the binding
    object.  "" can be passed in if the binding object is already stored in
    'obj'.

    callArgs should be code for getting a JS::CallArgs into a variable
    called 'args'.  This can be "" if there is already such a variable
    around or if the body does not need a JS::CallArgs.

    """

    def __init__(
        self,
        descriptor,
        name,
        args,
        getThisObj,
        callArgs="JS::CallArgs args = JS::CallArgsFromVp(argc, vp);\n",
    ):
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

        # This can't ever happen, because we only use this for class hooks.
        self.unwrapFailureCode = fill(
            """
            MOZ_CRASH("Unexpected object in '${name}' hook");
            return false;
            """,
            name=name,
        )

        if getThisObj == "":
            self.getThisObj = None
        else:
            self.getThisObj = CGGeneric(
                "JS::Rooted<JSObject*> obj(cx, %s);\n" % getThisObj
            )
        self.callArgs = callArgs

    def definition_body(self):
        body = self.callArgs
        if self.getThisObj is not None:
            body += self.getThisObj.define() + "\n"
        body += "%s* self;\n" % self.descriptor.nativeType
        body += dedent(
            """
            JS::Rooted<JS::Value> rootSelf(cx, JS::ObjectValue(*obj));
            """
        )

        body += str(
            CastableObjectUnwrapper(
                self.descriptor, "rootSelf", "&rootSelf", "self", self.unwrapFailureCode
            )
        )

        return body + self.generate_code().define()

    def generate_code(self):
        assert False  # Override me


class CGAbstractStaticBindingMethod(CGAbstractStaticMethod):
    """
    Common class to generate the JSNatives for all our static methods, getters
    and setters.  This will generate the function declaration and unwrap the
    global object.  Subclasses are expected to override the generate_code
    function to do the rest of the work.  This function should return a
    CGThing which is already properly indented.
    """

    def __init__(self, descriptor, name):
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", JSNativeArguments(), canRunScript=True
        )

    def definition_body(self):
        # Make sure that "obj" is in the same compartment as "cx", since we'll
        # later use it to wrap return values.
        unwrap = dedent(
            """
            JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
            JS::Rooted<JSObject*> obj(cx, &args.callee());

            """
        )
        return unwrap + self.generate_code().define()

    def generate_code(self):
        assert False  # Override me


def MakeNativeName(name):
    return name[0].upper() + IDLToCIdentifier(name[1:])


def GetWebExposedName(idlObject, descriptor):
    if idlObject == descriptor.operations["Stringifier"]:
        return "toString"
    name = idlObject.identifier.name
    if name == "__namedsetter":
        return "named setter"
    if name == "__namedgetter":
        return "named getter"
    if name == "__indexedsetter":
        return "indexed setter"
    if name == "__indexedgetter":
        return "indexed getter"
    if name == "__legacycaller":
        return "legacy caller"
    return name


def GetConstructorNameForReporting(descriptor, ctor):
    # Figure out the name of our constructor for reporting purposes.
    # For unnamed webidl constructors, identifier.name is "constructor" but
    # the name JS sees is the interface name; for legacy factory functions
    # identifier.name is the actual name.
    ctorName = ctor.identifier.name
    if ctorName == "constructor":
        return descriptor.interface.identifier.name
    return ctorName


def GetLabelForErrorReporting(descriptor, idlObject, isConstructor):
    """
    descriptor is the descriptor for the interface involved

    idlObject is the method (regular or static), attribute (regular or
    static), or constructor (named or not) involved.

    isConstructor is true if idlObject is a constructor and false otherwise.
    """
    if isConstructor:
        return "%s constructor" % GetConstructorNameForReporting(descriptor, idlObject)

    namePrefix = descriptor.interface.identifier.name
    name = GetWebExposedName(idlObject, descriptor)
    if " " in name:
        # It's got a space already, so just space-separate.
        return "%s %s" % (namePrefix, name)

    return "%s.%s" % (namePrefix, name)


class CGSpecializedMethod(CGAbstractStaticMethod):
    """
    A class for generating the C++ code for a specialized method that the JIT
    can call with lower overhead.
    """

    def __init__(self, descriptor, method):
        self.method = method
        name = CppKeywords.checkMethodName(IDLToCIdentifier(method.identifier.name))
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("const JSJitMethodCallArgs&", "args"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

    def definition_body(self):
        nativeName = CGSpecializedMethod.makeNativeName(self.descriptor, self.method)
        call = CGMethodCall(
            nativeName, self.method.isStatic(), self.descriptor, self.method
        ).define()
        prefix = ""
        if self.method.getExtendedAttribute("CrossOriginCallable"):
            for signature in self.method.signatures():
                # non-undefined signatures would require us to deal with remote proxies for the
                # return value here.
                if not signature[0].isUndefined():
                    raise TypeError(
                        "We don't support a method marked as CrossOriginCallable "
                        "with non-undefined return type"
                    )
            prototypeID, _ = PrototypeIDAndDepth(self.descriptor)
            prefix = fill(
                """
                // CrossOriginThisPolicy::UnwrapThisObject stores a ${nativeType}::RemoteProxy in void_self
                // if obj is a proxy with a RemoteObjectProxy handler for the right type, or else it stores
                // a ${nativeType}. If we get here from the JIT (without going through UnwrapThisObject) we
                // know void_self contains a ${nativeType}; we don't have special cases in the JIT to deal
                // with remote object proxies.
                if (IsRemoteObjectProxy(obj, ${prototypeID})) {
                    auto* self = static_cast<${nativeType}::RemoteProxy*>(void_self);
                    $*{call}
                }
                """,
                prototypeID=prototypeID,
                nativeType=self.descriptor.nativeType,
                call=call,
            )
        return prefix + fill(
            """
            auto* self = static_cast<${nativeType}*>(void_self);
            $*{call}
            """,
            nativeType=self.descriptor.nativeType,
            call=call,
        )

    def auto_profiler_label(self):
        interface_name = self.descriptor.interface.identifier.name
        method_name = self.method.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", "${method_name}", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_METHOD) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            method_name=method_name,
        )

    @staticmethod
    def should_have_method_description(descriptor, idlMethod):
        """
        Returns whether the given IDL method (static, non-static, constructor)
        should have a method description declaration, for use in error
        reporting.
        """
        # If a method has overloads, it needs a method description, because it
        # can throw MSG_INVALID_OVERLOAD_ARGCOUNT at the very least.
        if len(idlMethod.signatures()) != 1:
            return True

        # Methods with only one signature need a method description if one of
        # their args needs it.
        sig = idlMethod.signatures()[0]
        args = sig[1]
        return any(
            idlTypeNeedsCallContext(
                arg.type,
                descriptor,
                allowTreatNonCallableAsNull=arg.allowTreatNonCallableAsNull(),
            )
            for arg in args
        )

    @staticmethod
    def error_reporting_label_helper(descriptor, idlMethod, isConstructor):
        """
        Returns the method description to use for error reporting for the given
        IDL method.  Used to implement common error_reporting_label() functions
        across different classes.
        """
        if not CGSpecializedMethod.should_have_method_description(
            descriptor, idlMethod
        ):
            return None
        return '"%s"' % GetLabelForErrorReporting(descriptor, idlMethod, isConstructor)

    def error_reporting_label(self):
        return CGSpecializedMethod.error_reporting_label_helper(
            self.descriptor, self.method, isConstructor=False
        )

    @staticmethod
    def makeNativeName(descriptor, method):
        if method.underlyingAttr:
            return CGSpecializedGetterCommon.makeNativeName(
                descriptor, method.underlyingAttr
            )
        name = method.identifier.name
        return MakeNativeName(descriptor.binaryNameFor(name, method.isStatic()))


class CGMethodPromiseWrapper(CGAbstractStaticMethod):
    """
    A class for generating a wrapper around another method that will
    convert exceptions to promises.
    """

    def __init__(self, descriptor, methodToWrap):
        self.method = methodToWrap
        name = self.makeName(methodToWrap.name)
        args = list(methodToWrap.args)
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

    def definition_body(self):
        return fill(
            """
            bool ok = ${methodName}(${args});
            if (ok) {
              return true;
            }
            return ConvertExceptionToPromise(cx, args.rval());
            """,
            methodName=self.method.name,
            args=", ".join(arg.name for arg in self.args),
        )

    @staticmethod
    def makeName(methodName):
        return methodName + "_promiseWrapper"


class CGDefaultToJSONMethod(CGSpecializedMethod):
    def __init__(self, descriptor, method):
        assert method.isDefaultToJSON()
        CGSpecializedMethod.__init__(self, descriptor, method)

    def definition_body(self):
        ret = fill(
            """
            auto* self = static_cast<${nativeType}*>(void_self);
            JS::Rooted<JSObject*> result(cx, JS_NewPlainObject(cx));
            if (!result) {
              return false;
            }
            """,
            nativeType=self.descriptor.nativeType,
        )

        jsonDescriptors = [self.descriptor]
        interface = self.descriptor.interface.parent
        while interface:
            descriptor = self.descriptor.getDescriptor(interface.identifier.name)
            if descriptor.hasDefaultToJSON:
                jsonDescriptors.append(descriptor)
            interface = interface.parent

        # Iterate the array in reverse: oldest ancestor first
        for descriptor in jsonDescriptors[::-1]:
            ret += fill(
                """
                if (!${parentclass}::CollectJSONAttributes(cx, obj, MOZ_KnownLive(self), result)) {
                  return false;
                }
                """,
                parentclass=toBindingNamespace(descriptor.name),
            )
        ret += "args.rval().setObject(*result);\n" "return true;\n"
        return ret


class CGLegacyCallHook(CGAbstractBindingMethod):
    """
    Call hook for our object
    """

    def __init__(self, descriptor):
        self._legacycaller = descriptor.operations["LegacyCaller"]
        # Our "self" is actually the callee in this case, not the thisval.
        CGAbstractBindingMethod.__init__(
            self,
            descriptor,
            LEGACYCALLER_HOOK_NAME,
            JSNativeArguments(),
            getThisObj="&args.callee()",
        )

    def define(self):
        if not self._legacycaller:
            return ""
        return CGAbstractBindingMethod.define(self)

    def generate_code(self):
        name = self._legacycaller.identifier.name
        nativeName = MakeNativeName(self.descriptor.binaryNameFor(name, False))
        return CGMethodCall(nativeName, False, self.descriptor, self._legacycaller)

    def error_reporting_label(self):
        # Should act like methods.
        return CGSpecializedMethod.error_reporting_label_helper(
            self.descriptor, self._legacycaller, isConstructor=False
        )


class CGResolveHook(CGAbstractClassHook):
    """
    Resolve hook for objects that have the NeedResolve extended attribute.
    """

    def __init__(self, descriptor):
        assert descriptor.interface.getExtendedAttribute("NeedResolve")

        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("bool*", "resolvedp"),
        ]
        CGAbstractClassHook.__init__(self, descriptor, RESOLVE_HOOK_NAME, "bool", args)

    def generate_code(self):
        return dedent(
            """
            JS::Rooted<mozilla::Maybe<JS::PropertyDescriptor>> desc(cx);
            if (!self->DoResolve(cx, obj, id, &desc)) {
              return false;
            }
            if (desc.isNothing()) {
              return true;
            }
            // If desc.value() is undefined, then the DoResolve call
            // has already defined it on the object.  Don't try to also
            // define it.
            MOZ_ASSERT(desc->isDataDescriptor());
            if (!desc->value().isUndefined()) {
              JS::Rooted<JS::PropertyDescriptor> defineDesc(cx, *desc);
              defineDesc.setResolving(true);
              if (!JS_DefinePropertyById(cx, obj, id, defineDesc)) {
                return false;
              }
            }
            *resolvedp = true;
            return true;
            """
        )

    def definition_body(self):
        if self.descriptor.isGlobal():
            # Resolve standard classes
            prefix = dedent(
                """
                if (!ResolveGlobal(cx, obj, id, resolvedp)) {
                  return false;
                }
                if (*resolvedp) {
                  return true;
                }

                """
            )
        else:
            prefix = ""
        return prefix + CGAbstractClassHook.definition_body(self)


class CGMayResolveHook(CGAbstractStaticMethod):
    """
    Resolve hook for objects that have the NeedResolve extended attribute.
    """

    def __init__(self, descriptor):
        assert descriptor.interface.getExtendedAttribute("NeedResolve")

        args = [
            Argument("const JSAtomState&", "names"),
            Argument("jsid", "id"),
            Argument("JSObject*", "maybeObj"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, MAY_RESOLVE_HOOK_NAME, "bool", args
        )

    def definition_body(self):
        if self.descriptor.isGlobal():
            # Check whether this would resolve as a standard class.
            prefix = dedent(
                """
                if (MayResolveGlobal(names, id, maybeObj)) {
                  return true;
                }

                """
            )
        else:
            prefix = ""
        return prefix + "return %s::MayResolve(id);\n" % self.descriptor.nativeType


class CGEnumerateHook(CGAbstractBindingMethod):
    """
    Enumerate hook for objects with custom hooks.
    """

    def __init__(self, descriptor):
        assert descriptor.interface.getExtendedAttribute("NeedResolve")

        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("JS::MutableHandleVector<jsid>", "properties"),
            Argument("bool", "enumerableOnly"),
        ]
        # Our "self" is actually the "obj" argument in this case, not the thisval.
        CGAbstractBindingMethod.__init__(
            self, descriptor, NEW_ENUMERATE_HOOK_NAME, args, getThisObj="", callArgs=""
        )

    def generate_code(self):
        return CGGeneric(
            dedent(
                """
            FastErrorResult rv;
            self->GetOwnPropertyNames(cx, properties, enumerableOnly, rv);
            if (rv.MaybeSetPendingException(cx)) {
              return false;
            }
            return true;
            """
            )
        )

    def definition_body(self):
        if self.descriptor.isGlobal():
            # Enumerate standard classes
            prefix = dedent(
                """
                if (!EnumerateGlobal(cx, obj, properties, enumerableOnly)) {
                  return false;
                }

                """
            )
        else:
            prefix = ""
        return prefix + CGAbstractBindingMethod.definition_body(self)


class CppKeywords:
    """
    A class for checking if method names declared in webidl
    are not in conflict with C++ keywords.
    """

    keywords = frozenset(
        [
            "alignas",
            "alignof",
            "and",
            "and_eq",
            "asm",
            "assert",
            "auto",
            "bitand",
            "bitor",
            "bool",
            "break",
            "case",
            "catch",
            "char",
            "char16_t",
            "char32_t",
            "class",
            "compl",
            "const",
            "constexpr",
            "const_cast",
            "continue",
            "decltype",
            "default",
            "delete",
            "do",
            "double",
            "dynamic_cast",
            "else",
            "enum",
            "explicit",
            "export",
            "extern",
            "false",
            "final",
            "float",
            "for",
            "friend",
            "goto",
            "if",
            "inline",
            "int",
            "long",
            "mutable",
            "namespace",
            "new",
            "noexcept",
            "not",
            "not_eq",
            "nullptr",
            "operator",
            "or",
            "or_eq",
            "override",
            "private",
            "protected",
            "public",
            "register",
            "reinterpret_cast",
            "return",
            "short",
            "signed",
            "sizeof",
            "static",
            "static_assert",
            "static_cast",
            "struct",
            "switch",
            "template",
            "this",
            "thread_local",
            "throw",
            "true",
            "try",
            "typedef",
            "typeid",
            "typename",
            "union",
            "unsigned",
            "using",
            "virtual",
            "void",
            "volatile",
            "wchar_t",
            "while",
            "xor",
            "xor_eq",
        ]
    )

    @staticmethod
    def checkMethodName(name):
        # Double '_' because 'assert' and '_assert' cannot be used in MS2013 compiler.
        # Bug 964892 and bug 963560.
        if name in CppKeywords.keywords:
            name = "_" + name + "_"
        return name


class CGStaticMethod(CGAbstractStaticBindingMethod):
    """
    A class for generating the C++ code for an IDL static method.
    """

    def __init__(self, descriptor, method):
        self.method = method
        name = CppKeywords.checkMethodName(IDLToCIdentifier(method.identifier.name))
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name)

    def generate_code(self):
        nativeName = CGSpecializedMethod.makeNativeName(self.descriptor, self.method)
        return CGMethodCall(nativeName, True, self.descriptor, self.method)

    def auto_profiler_label(self):
        interface_name = self.descriptor.interface.identifier.name
        method_name = self.method.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", "${method_name}", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_METHOD) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            method_name=method_name,
        )

    def error_reporting_label(self):
        return CGSpecializedMethod.error_reporting_label_helper(
            self.descriptor, self.method, isConstructor=False
        )


class CGSpecializedGetterCommon(CGAbstractStaticMethod):
    """
    A class for generating the code for a specialized attribute getter
    that the JIT can call with lower overhead.
    """

    def __init__(
        self,
        descriptor,
        name,
        nativeName,
        attr,
        args,
        errorReportingLabel=None,
        additionalArg=None,
    ):
        self.nativeName = nativeName
        self.errorReportingLabel = errorReportingLabel
        self.additionalArgs = [] if additionalArg is None else [additionalArg]
        # StoreInSlot attributes have their getters called from Wrap().  We
        # really hope they can't run script, and don't want to annotate Wrap()
        # methods as doing that anyway, so let's not annotate them as
        # MOZ_CAN_RUN_SCRIPT.
        CGAbstractStaticMethod.__init__(
            self,
            descriptor,
            name,
            "bool",
            args + self.additionalArgs,
            canRunScript=not attr.getExtendedAttribute("StoreInSlot"),
        )

    def definition_body(self):
        prefix = fill(
            """
            auto* self = static_cast<${nativeType}*>(void_self);
            """,
            nativeType=self.descriptor.nativeType,
        )

        if self.attr.isMaplikeOrSetlikeAttr():
            assert not self.attr.getExtendedAttribute("CrossOriginReadable")
            # If the interface is maplike/setlike, there will be one getter
            # method for the size property of the backing object. Due to having
            # to unpack the backing object from the slot, this requires its own
            # generator.
            return prefix + getMaplikeOrSetlikeSizeGetterBody(
                self.descriptor, self.attr
            )

        if self.attr.type.isObservableArray():
            assert not self.attr.getExtendedAttribute("CrossOriginReadable")
            # If the attribute is observableArray, due to having to unpack the
            # backing object from the slot, this requires its own generator.
            return prefix + getObservableArrayGetterBody(self.descriptor, self.attr)

        if self.nativeName is None:
            nativeName = CGSpecializedGetterCommon.makeNativeName(
                self.descriptor, self.attr
            )
        else:
            nativeName = self.nativeName

        type = self.attr.type
        if self.attr.getExtendedAttribute("CrossOriginReadable"):
            remoteType = type
            extendedAttributes = self.descriptor.getExtendedAttributes(
                self.attr, getter=True
            )
            if (
                remoteType.isGeckoInterface()
                and not remoteType.unroll().inner.isExternal()
                and remoteType.unroll().inner.getExtendedAttribute("ChromeOnly") is None
            ):
                # We'll use a JSObject. It might make more sense to use remoteType's
                # RemoteProxy, but it's not easy to construct a type for that from here.
                remoteType = BuiltinTypes[IDLBuiltinType.Types.object]
                if "needsErrorResult" not in extendedAttributes:
                    extendedAttributes.append("needsErrorResult")
            prototypeID, _ = PrototypeIDAndDepth(self.descriptor)
            prefix = (
                fill(
                    """
                if (IsRemoteObjectProxy(obj, ${prototypeID})) {
                    ${nativeType}::RemoteProxy* self = static_cast<${nativeType}::RemoteProxy*>(void_self);
                    $*{call}
                }
            """,
                    prototypeID=prototypeID,
                    nativeType=self.descriptor.nativeType,
                    call=CGGetterCall(
                        remoteType,
                        nativeName,
                        self.descriptor,
                        self.attr,
                        self.errorReportingLabel,
                        argsPre=[a.name for a in self.additionalArgs],
                        dontSetSlot=True,
                        extendedAttributes=extendedAttributes,
                    ).define(),
                )
                + prefix
            )

        argsPre = [a.name for a in self.additionalArgs]
        maybeReturnCachedVal = None
        if self.attr.slotIndices is not None:
            # We're going to store this return value in a slot on some object,
            # to cache it.  The question is, which object?  For dictionary and
            # sequence return values, we want to use a slot on the Xray expando
            # if we're called via Xrays, and a slot on our reflector otherwise.
            # On the other hand, when dealing with some interface types
            # (e.g. window.document) we want to avoid calling the getter more
            # than once.  In the case of window.document, it's because the
            # getter can start returning null, which would get hidden in the
            # non-Xray case by the fact that it's [StoreOnSlot], so the cached
            # version is always around.
            #
            # The upshot is that we use the reflector slot for any getter whose
            # type is a gecko interface, whether we're called via Xrays or not.
            # Since [Cached] and [StoreInSlot] cannot be used with "NewObject",
            # we know that in the interface type case the returned object is
            # wrappercached.  So creating Xrays to it is reasonable.
            if mayUseXrayExpandoSlots(self.descriptor, self.attr):
                prefix += dedent(
                    """
                    // Have to either root across the getter call or reget after.
                    bool isXray;
                    JS::Rooted<JSObject*> slotStorage(cx, GetCachedSlotStorageObject(cx, obj, &isXray));
                    if (!slotStorage) {
                      return false;
                    }
                    """
                )
            else:
                prefix += dedent(
                    """
                    // Have to either root across the getter call or reget after.
                    JS::Rooted<JSObject*> slotStorage(cx, js::UncheckedUnwrap(obj, /* stopAtWindowProxy = */ false));
                    MOZ_ASSERT(IsDOMObject(slotStorage));
                    """
                )

            if self.attr.getExtendedAttribute(
                "ReflectedHTMLAttributeReturningFrozenArray"
            ):
                argsPre.append("hasCachedValue ? &useCachedValue : nullptr")
                isXray = (
                    "isXray"
                    if mayUseXrayExpandoSlots(self.descriptor, self.attr)
                    else "false"
                )
                prefix += fill(
                    """
                    auto& array = ReflectedHTMLAttributeSlots::GetOrCreate(slotStorage, ${isXray});
                    JS::Rooted<JS::Value> cachedVal(cx, array[${arrayIndex}]);
                    bool hasCachedValue = !cachedVal.isUndefined();
                    bool useCachedValue = false;
                    """,
                    isXray=isXray,
                    arrayIndex=reflectedHTMLAttributesArrayIndex(
                        self.descriptor, self.attr
                    ),
                )
                maybeReturnCachedVal = fill(
                    """
                    MOZ_ASSERT_IF(useCachedValue, hasCachedValue);
                    if (hasCachedValue && useCachedValue) {
                      args.rval().set(cachedVal);
                      // The cached value is in the compartment of slotStorage,
                      // so wrap into the caller compartment as needed.
                      return ${maybeWrap}(cx, args.rval());
                    }

                    ${clearCachedValue}(self);

                    """,
                    maybeWrap=getMaybeWrapValueFuncForType(self.attr.type),
                    clearCachedValue=MakeClearCachedValueNativeName(self.attr),
                )
            else:
                if mayUseXrayExpandoSlots(self.descriptor, self.attr):
                    prefix += fill(
                        """
                        const size_t slotIndex = isXray ? ${xraySlotIndex} : ${slotIndex};
                        """,
                        xraySlotIndex=memberXrayExpandoReservedSlot(
                            self.attr, self.descriptor
                        ),
                        slotIndex=memberReservedSlot(self.attr, self.descriptor),
                    )
                else:
                    prefix += fill(
                        """
                        const size_t slotIndex = ${slotIndex};
                        """,
                        slotIndex=memberReservedSlot(self.attr, self.descriptor),
                    )
                prefix += fill(
                    """
                    MOZ_ASSERT(slotIndex < JSCLASS_RESERVED_SLOTS(JS::GetClass(slotStorage)));
                    {
                      // Scope for cachedVal
                      JS::Value cachedVal = JS::GetReservedSlot(slotStorage, slotIndex);
                      if (!cachedVal.isUndefined()) {
                        args.rval().set(cachedVal);
                        // The cached value is in the compartment of slotStorage,
                        // so wrap into the caller compartment as needed.
                        return ${maybeWrap}(cx, args.rval());
                      }
                    }

                    """,
                    maybeWrap=getMaybeWrapValueFuncForType(self.attr.type),
                )

        return (
            prefix
            + CGGetterCall(
                type,
                nativeName,
                self.descriptor,
                self.attr,
                self.errorReportingLabel,
                argsPre=argsPre,
                preConversionCode=maybeReturnCachedVal,
            ).define()
        )

    def auto_profiler_label(self, profilerLabel=None):
        if profilerLabel is None:
            profilerLabel = '"' + self.attr.identifier.name + '"'
        interface_name = self.descriptor.interface.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", ${attr_name}, DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_GETTER) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            attr_name=profilerLabel,
        )

    def error_reporting_label(self):
        # Getters never need a BindingCallContext.
        return None

    @staticmethod
    def makeNativeName(descriptor, attr):
        name = attr.identifier.name
        nativeName = MakeNativeName(descriptor.binaryNameFor(name, attr.isStatic()))
        _, resultOutParam, _, _, _ = getRetvalDeclarationForType(attr.type, descriptor)
        extendedAttrs = descriptor.getExtendedAttributes(attr, getter=True)
        canFail = "needsErrorResult" in extendedAttrs or "canOOM" in extendedAttrs
        if resultOutParam or attr.type.nullable() or canFail:
            nativeName = "Get" + nativeName
        return nativeName


class CGSpecializedGetter(CGSpecializedGetterCommon):
    """
    A class for generating the code for a specialized attribute getter
    that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        self.attr = attr
        name = "get_" + IDLToCIdentifier(attr.identifier.name)
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitGetterCallArgs", "args"),
        ]
        CGSpecializedGetterCommon.__init__(self, descriptor, name, None, attr, args)


class CGTemplateForSpecializedGetter(CGSpecializedGetterCommon):
    """
    A class for generating the code for a specialized attribute getter
    that can be used as the common getter that templated attribute
    getters can forward to.
    """

    def __init__(self, descriptor, template):
        self.attr = template.attr
        self.attrNameString = template.attrNameString
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitGetterCallArgs", "args"),
        ]
        errorDescription = (
            'ErrorDescriptionFor<ErrorFor::getter>{ "%s", attrName }'
            % descriptor.interface.identifier.name
        )
        CGSpecializedGetterCommon.__init__(
            self,
            descriptor,
            template.getter,
            template.getter,
            self.attr,
            args,
            errorReportingLabel=errorDescription,
            additionalArg=Argument(template.argument.type, template.argument.name),
        )

    def auto_profiler_label(self):
        return (
            fill(
                """
                const char* attrName = ${attrNameString};
                """,
                attrNameString=self.attrNameString,
            )
            + CGSpecializedGetterCommon.auto_profiler_label(self, "attrName")
        )


class CGSpecializedTemplatedGetter(CGAbstractStaticMethod):
    """
    A class for generating the code for a specialized templated attribute
    getter that forwards to a common template getter.
    """

    def __init__(self, descriptor, attr, template, additionalArg):
        self.attr = attr
        self.template = template
        self.additionalArg = additionalArg
        name = "get_" + IDLToCIdentifier(attr.identifier.name)
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitGetterCallArgs", "args"),
        ]
        assert not attr.getExtendedAttribute("StoreInSlot")
        CGAbstractStaticMethod.__init__(
            self,
            descriptor,
            name,
            "bool",
            args,
            canRunScript=True,
        )

    def definition_body(self):
        if self.additionalArg is None:
            additionalArg = self.attr.identifier.name
        else:
            additionalArg = self.additionalArg

        return fill(
            """
            return ${namespace}::${getter}(cx, obj, void_self, args, ${additionalArg});
            """,
            namespace=toBindingNamespace(
                self.template.descriptor.interface.identifier.name
            ),
            getter=self.template.getter,
            additionalArg=additionalArg,
        )


class CGGetterPromiseWrapper(CGAbstractStaticMethod):
    """
    A class for generating a wrapper around another getter that will
    convert exceptions to promises.
    """

    def __init__(self, descriptor, getterToWrap):
        self.getter = getterToWrap
        name = self.makeName(getterToWrap.name)
        args = list(getterToWrap.args)
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

    def definition_body(self):
        return fill(
            """
            bool ok = ${getterName}(${args});
            if (ok) {
              return true;
            }
            return ConvertExceptionToPromise(cx, args.rval());
            """,
            getterName=self.getter.name,
            args=", ".join(arg.name for arg in self.args),
        )

    @staticmethod
    def makeName(getterName):
        return getterName + "_promiseWrapper"


class CGStaticGetter(CGAbstractStaticBindingMethod):
    """
    A class for generating the C++ code for an IDL static attribute getter.
    """

    def __init__(self, descriptor, attr):
        self.attr = attr
        name = "get_" + IDLToCIdentifier(attr.identifier.name)
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name)

    def generate_code(self):
        nativeName = CGSpecializedGetterCommon.makeNativeName(
            self.descriptor, self.attr
        )
        return CGGetterCall(self.attr.type, nativeName, self.descriptor, self.attr)

    def auto_profiler_label(self):
        interface_name = self.descriptor.interface.identifier.name
        attr_name = self.attr.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", "${attr_name}", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_GETTER) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            attr_name=attr_name,
        )

    def error_reporting_label(self):
        # Getters never need a BindingCallContext.
        return None


class CGSpecializedSetterCommon(CGAbstractStaticMethod):
    """
    A class for generating the code for a specialized attribute setter
    that the JIT can call with lower overhead.
    """

    def __init__(
        self,
        descriptor,
        name,
        nativeName,
        attr,
        args,
        errorReportingLabel=None,
        additionalArg=None,
    ):
        self.nativeName = nativeName
        self.errorReportingLabel = errorReportingLabel
        self.additionalArgs = [] if additionalArg is None else [additionalArg]
        CGAbstractStaticMethod.__init__(
            self,
            descriptor,
            name,
            "bool",
            args + self.additionalArgs,
            canRunScript=True,
        )

    def definition_body(self):
        type = self.attr.type
        call = CGSetterCall(
            type,
            self.nativeName,
            self.descriptor,
            self.attr,
            self.errorReportingLabel,
            [a.name for a in self.additionalArgs],
        ).define()
        prefix = ""
        if self.attr.getExtendedAttribute("CrossOriginWritable"):
            if type.isGeckoInterface() and not type.unroll().inner.isExternal():
                # a setter taking a Gecko interface would require us to deal with remote
                # proxies for the value here.
                raise TypeError(
                    "We don't support the setter of %s marked as "
                    "CrossOriginWritable because it takes a Gecko interface "
                    "as the value",
                    self.attr.identifier.name,
                )
            prototypeID, _ = PrototypeIDAndDepth(self.descriptor)
            prefix = fill(
                """
                if (IsRemoteObjectProxy(obj, ${prototypeID})) {
                    auto* self = static_cast<${nativeType}::RemoteProxy*>(void_self);
                    $*{call}
                }
                """,
                prototypeID=prototypeID,
                nativeType=self.descriptor.nativeType,
                call=call,
            )

        return prefix + fill(
            """
            auto* self = static_cast<${nativeType}*>(void_self);
            $*{call}
            """,
            nativeType=self.descriptor.nativeType,
            call=call,
        )

    def auto_profiler_label(self, profilerLabel=None):
        interface_name = self.descriptor.interface.identifier.name
        if profilerLabel is None:
            profilerLabel = '"' + self.attr.identifier.name + '"'
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", ${attr_name}, DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_SETTER) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            attr_name=profilerLabel,
        )

    @staticmethod
    def error_reporting_label_helper(descriptor, attr):
        # Setters need a BindingCallContext if the type of the attribute needs
        # one.
        if not idlTypeNeedsCallContext(
            attr.type, descriptor, allowTreatNonCallableAsNull=True
        ):
            return None
        return '"%s"' % (
            GetLabelForErrorReporting(descriptor, attr, isConstructor=False) + " setter"
        )

    def error_reporting_label(self):
        errorReportingLabel = CGSpecializedSetterCommon.error_reporting_label_helper(
            self.descriptor, self.attr
        )
        if errorReportingLabel is None:
            return None
        if self.errorReportingLabel:
            return self.errorReportingLabel
        return errorReportingLabel

    @staticmethod
    def makeNativeName(descriptor, attr):
        name = attr.identifier.name
        return "Set" + MakeNativeName(descriptor.binaryNameFor(name, attr.isStatic()))


class CGSpecializedSetter(CGSpecializedSetterCommon):
    """
    A class for generating the code for a specialized attribute setter
    that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        self.attr = attr
        name = "set_" + IDLToCIdentifier(attr.identifier.name)
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitSetterCallArgs", "args"),
        ]
        CGSpecializedSetterCommon.__init__(
            self,
            descriptor,
            name,
            CGSpecializedSetterCommon.makeNativeName(descriptor, attr),
            attr,
            args,
        )


class CGTemplateForSpecializedSetter(CGSpecializedSetterCommon):
    """
    A class for generating the code for a specialized attribute setter
    that can be used as the common setter that templated attribute
    setters can forward to.
    """

    def __init__(self, descriptor, template):
        self.attr = template.attr
        self.attrNameString = template.attrNameString
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitSetterCallArgs", "args"),
        ]
        errorDescription = (
            'ErrorDescriptionFor<ErrorFor::setter>{ "%s", attrName }'
            % descriptor.interface.identifier.name
        )
        CGSpecializedSetterCommon.__init__(
            self,
            descriptor,
            template.setter,
            template.setter,
            self.attr,
            args,
            errorReportingLabel=errorDescription,
            additionalArg=Argument(template.argument.type, template.argument.name),
        )

    def auto_profiler_label(self):
        return (
            fill(
                """
                const char* attrName = ${attrNameString};
                """,
                attrNameString=self.attrNameString,
            )
            + CGSpecializedSetterCommon.auto_profiler_label(self, "attrName")
        )


class CGSpecializedTemplatedSetter(CGAbstractStaticMethod):
    """
    A class for generating the code for a specialized templated attribute
    setter that forwards to a common template setter.
    """

    def __init__(self, descriptor, attr, template, additionalArg):
        self.attr = attr
        self.template = template
        self.additionalArg = additionalArg
        name = "set_" + IDLToCIdentifier(attr.identifier.name)
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitSetterCallArgs", "args"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

    def definition_body(self):
        additionalArgs = []
        if self.additionalArg is None:
            additionalArgs.append(self.attr.identifier.name)
        else:
            additionalArgs.append(self.additionalArg)

        return fill(
            """
            return ${namespace}::${setter}(cx, obj, void_self, args, ${additionalArgs});
            """,
            namespace=toBindingNamespace(
                self.template.descriptor.interface.identifier.name
            ),
            setter=self.template.setter,
            additionalArgs=", ".join(additionalArgs),
        )


class CGStaticSetter(CGAbstractStaticBindingMethod):
    """
    A class for generating the C++ code for an IDL static attribute setter.
    """

    def __init__(self, descriptor, attr):
        self.attr = attr
        name = "set_" + IDLToCIdentifier(attr.identifier.name)
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name)

    def generate_code(self):
        nativeName = CGSpecializedSetterCommon.makeNativeName(
            self.descriptor, self.attr
        )
        checkForArg = CGGeneric(
            fill(
                """
            if (!args.requireAtLeast(cx, "${name} setter", 1)) {
              return false;
            }
            """,
                name=self.attr.identifier.name,
            )
        )
        call = CGSetterCall(self.attr.type, nativeName, self.descriptor, self.attr)
        return CGList([checkForArg, call])

    def auto_profiler_label(self):
        interface_name = self.descriptor.interface.identifier.name
        attr_name = self.attr.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", "${attr_name}", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_SETTER) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            attr_name=attr_name,
        )

    def error_reporting_label(self):
        return CGSpecializedSetterCommon.error_reporting_label_helper(
            self.descriptor, self.attr
        )


class CGSpecializedForwardingSetter(CGSpecializedSetter):
    """
    A class for generating the code for a specialized attribute setter with
    PutForwards that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        CGSpecializedSetter.__init__(self, descriptor, attr)

    def definition_body(self):
        attrName = self.attr.identifier.name
        forwardToAttrName = self.attr.getExtendedAttribute("PutForwards")[0]
        # JS_GetProperty and JS_SetProperty can only deal with ASCII
        assert all(ord(c) < 128 for c in attrName)
        assert all(ord(c) < 128 for c in forwardToAttrName)
        return fill(
            """
            JS::Rooted<JS::Value> v(cx);
            if (!JS_GetProperty(cx, obj, "${attr}", &v)) {
              return false;
            }

            if (!v.isObject()) {
              return cx.ThrowErrorMessage<MSG_NOT_OBJECT>("${interface}.${attr}");
            }

            JS::Rooted<JSObject*> targetObj(cx, &v.toObject());
            return JS_SetProperty(cx, targetObj, "${forwardToAttrName}", args[0]);
            """,
            attr=attrName,
            interface=self.descriptor.interface.identifier.name,
            forwardToAttrName=forwardToAttrName,
        )

    def error_reporting_label(self):
        # We always need to be able to throw.
        return '"%s"' % (
            GetLabelForErrorReporting(self.descriptor, self.attr, isConstructor=False)
            + " setter"
        )


class CGSpecializedReplaceableSetter(CGSpecializedSetter):
    """
    A class for generating the code for a specialized attribute setter with
    Replaceable that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        CGSpecializedSetter.__init__(self, descriptor, attr)

    def definition_body(self):
        attrName = self.attr.identifier.name
        # JS_DefineProperty can only deal with ASCII
        assert all(ord(c) < 128 for c in attrName)
        return (
            'return JS_DefineProperty(cx, obj, "%s", args[0], JSPROP_ENUMERATE);\n'
            % attrName
        )

    def error_reporting_label(self):
        # We never throw directly.
        return None


class CGSpecializedLenientSetter(CGSpecializedSetter):
    """
    A class for generating the code for a specialized attribute setter with
    LenientSetter that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        CGSpecializedSetter.__init__(self, descriptor, attr)

    def definition_body(self):
        attrName = self.attr.identifier.name
        # JS_DefineProperty can only deal with ASCII
        assert all(ord(c) < 128 for c in attrName)
        return dedent(
            """
            DeprecationWarning(cx, obj, DeprecatedOperations::eLenientSetter);
            return true;
            """
        )

    def error_reporting_label(self):
        # We never throw; that's the whole point.
        return None


def memberReturnsNewObject(member):
    return member.getExtendedAttribute("NewObject") is not None


class CGMemberJITInfo(CGThing):
    """
    A class for generating the JITInfo for a property that points to
    our specialized getter and setter.
    """

    def __init__(self, descriptor, member):
        self.member = member
        self.descriptor = descriptor

    def declare(self):
        return ""

    def defineJitInfo(
        self,
        infoName,
        opName,
        opType,
        infallible,
        movable,
        eliminatable,
        aliasSet,
        alwaysInSlot,
        lazilyInSlot,
        slotIndex,
        returnTypes,
        args,
    ):
        """
        aliasSet is a JSJitInfo::AliasSet value, without the "JSJitInfo::" bit.

        args is None if we don't want to output argTypes for some
        reason (e.g. we have overloads or we're not a method) and
        otherwise an iterable of the arguments for this method.
        """
        assert (
            not movable or aliasSet != "AliasEverything"
        )  # Can't move write-aliasing things
        assert (
            not alwaysInSlot or movable
        )  # Things always in slots had better be movable
        assert (
            not eliminatable or aliasSet != "AliasEverything"
        )  # Can't eliminate write-aliasing things
        assert (
            not alwaysInSlot or eliminatable
        )  # Things always in slots had better be eliminatable

        def jitInfoInitializer(isTypedMethod):
            initializer = fill(
                """
                {
                  { ${opName} },
                  { prototypes::id::${name} },
                  { PrototypeTraits<prototypes::id::${name}>::Depth },
                  JSJitInfo::${opType},
                  JSJitInfo::${aliasSet}, /* aliasSet.  Not relevant for setters. */
                  ${returnType},  /* returnType.  Not relevant for setters. */
                  ${isInfallible},  /* isInfallible. False in setters. */
                  ${isMovable},  /* isMovable.  Not relevant for setters. */
                  ${isEliminatable}, /* isEliminatable.  Not relevant for setters. */
                  ${isAlwaysInSlot}, /* isAlwaysInSlot.  Only relevant for getters. */
                  ${isLazilyCachedInSlot}, /* isLazilyCachedInSlot.  Only relevant for getters. */
                  ${isTypedMethod},  /* isTypedMethod.  Only relevant for methods. */
                  ${slotIndex}   /* Reserved slot index, if we're stored in a slot, else 0. */
                }
                """,
                opName=opName,
                name=self.descriptor.name,
                opType=opType,
                aliasSet=aliasSet,
                returnType=functools.reduce(
                    CGMemberJITInfo.getSingleReturnType, returnTypes, ""
                ),
                isInfallible=toStringBool(infallible),
                isMovable=toStringBool(movable),
                isEliminatable=toStringBool(eliminatable),
                isAlwaysInSlot=toStringBool(alwaysInSlot),
                isLazilyCachedInSlot=toStringBool(lazilyInSlot),
                isTypedMethod=toStringBool(isTypedMethod),
                slotIndex="0" if slotIndex is None else slotIndex,
            )
            return initializer.rstrip()

        if slotIndex is not None:
            slotAssert = fill(
                """
                static_assert(${slotIndex} <= JSJitInfo::maxSlotIndex, "We won't fit");
                static_assert(${slotIndex} < ${classReservedSlots}, "There is no slot for us");
                """,
                slotIndex=slotIndex,
                classReservedSlots=INSTANCE_RESERVED_SLOTS
                + self.descriptor.interface.totalMembersInSlots,
            )
        else:
            slotAssert = ""
        if args is not None:
            argTypes = "%s_argTypes" % infoName
            args = [CGMemberJITInfo.getJSArgType(arg.type) for arg in args]
            args.append("JSJitInfo::ArgTypeListEnd")
            argTypesDecl = "static const JSJitInfo::ArgType %s[] = { %s };\n" % (
                argTypes,
                ", ".join(args),
            )
            return fill(
                """
                $*{argTypesDecl}
                static const JSTypedMethodJitInfo ${infoName} = {
                ${jitInfo},
                  ${argTypes}
                };
                $*{slotAssert}
                """,
                argTypesDecl=argTypesDecl,
                infoName=infoName,
                jitInfo=indent(jitInfoInitializer(True)),
                argTypes=argTypes,
                slotAssert=slotAssert,
            )

        # Unexposed things are meant to be used from C++ directly, so we make
        # their jitinfo non-static.  That way C++ can get at it.
        if self.member.getExtendedAttribute("Unexposed"):
            storageClass = "extern"
        else:
            storageClass = "static"

        return fill(
            """
            ${storageClass} const JSJitInfo ${infoName} = ${jitInfo};
            $*{slotAssert}
            """,
            storageClass=storageClass,
            infoName=infoName,
            jitInfo=jitInfoInitializer(False),
            slotAssert=slotAssert,
        )

    def define(self):
        if self.member.isAttr():
            getterinfo = "%s_getterinfo" % IDLToCIdentifier(self.member.identifier.name)
            name = IDLToCIdentifier(self.member.identifier.name)
            if self.member.type.isPromise():
                name = CGGetterPromiseWrapper.makeName(name)
            getter = "get_%s" % name
            extendedAttrs = self.descriptor.getExtendedAttributes(
                self.member, getter=True
            )
            getterinfal = "needsErrorResult" not in extendedAttrs

            # At this point getterinfal is true if our getter either can't throw
            # at all, or can only throw OOM.  In both cases, it's safe to move,
            # or dead-code-eliminate, the getter, because throwing OOM is not
            # semantically meaningful, so code can't rely on it happening.  Note
            # that this makes the behavior consistent for OOM thrown from the
            # getter itself and OOM thrown from the to-JS conversion of the
            # return value (see the "canOOM" and "infallibleForMember" checks
            # below).
            movable = self.mayBeMovable() and getterinfal
            eliminatable = self.mayBeEliminatable() and getterinfal
            aliasSet = self.aliasSet()

            # Now we have to set getterinfal to whether we can _really_ ever
            # throw, from the point of view of the JS engine.
            getterinfal = (
                getterinfal
                and "canOOM" not in extendedAttrs
                and infallibleForMember(self.member, self.member.type, self.descriptor)
            )
            isAlwaysInSlot = self.member.getExtendedAttribute("StoreInSlot")

            if self.member.slotIndices is not None:
                assert (
                    isAlwaysInSlot
                    or self.member.getExtendedAttribute("Cached")
                    or self.member.getExtendedAttribute(
                        "ReflectedHTMLAttributeReturningFrozenArray"
                    )
                    or self.member.type.isObservableArray()
                )
                isLazilyCachedInSlot = (
                    not isAlwaysInSlot
                    and not self.member.getExtendedAttribute(
                        "ReflectedHTMLAttributeReturningFrozenArray"
                    )
                )
                slotIndex = memberReservedSlot(self.member, self.descriptor)
                # We'll statically assert that this is not too big in
                # CGUpdateMemberSlotsMethod, in the case when
                # isAlwaysInSlot is true.
            else:
                isLazilyCachedInSlot = False
                slotIndex = None

            result = self.defineJitInfo(
                getterinfo,
                getter,
                "Getter",
                getterinfal,
                movable,
                eliminatable,
                aliasSet,
                isAlwaysInSlot,
                isLazilyCachedInSlot,
                slotIndex,
                [self.member.type],
                None,
            )
            if (
                not self.member.readonly
                or self.member.getExtendedAttribute("PutForwards") is not None
                or self.member.getExtendedAttribute("Replaceable") is not None
                or self.member.getExtendedAttribute("LegacyLenientSetter") is not None
            ):
                setterinfo = "%s_setterinfo" % IDLToCIdentifier(
                    self.member.identifier.name
                )
                # Actually a JSJitSetterOp, but JSJitGetterOp is first in the
                # union.
                setter = "(JSJitGetterOp)set_%s" % IDLToCIdentifier(
                    self.member.identifier.name
                )
                # Setters are always fallible, since they have to do a typed unwrap.
                result += self.defineJitInfo(
                    setterinfo,
                    setter,
                    "Setter",
                    False,
                    False,
                    False,
                    "AliasEverything",
                    False,
                    False,
                    None,
                    [BuiltinTypes[IDLBuiltinType.Types.undefined]],
                    None,
                )
            return result
        if self.member.isMethod():
            methodinfo = "%s_methodinfo" % IDLToCIdentifier(self.member.identifier.name)
            name = CppKeywords.checkMethodName(
                IDLToCIdentifier(self.member.identifier.name)
            )
            if self.member.returnsPromise():
                name = CGMethodPromiseWrapper.makeName(name)
            # Actually a JSJitMethodOp, but JSJitGetterOp is first in the union.
            method = "(JSJitGetterOp)%s" % name

            # Methods are infallible if they are infallible, have no arguments
            # to unwrap, and have a return type that's infallible to wrap up for
            # return.
            sigs = self.member.signatures()
            if len(sigs) != 1:
                # Don't handle overloading.  If there's more than one signature,
                # one of them must take arguments.
                methodInfal = False
                args = None
                movable = False
                eliminatable = False
            else:
                sig = sigs[0]
                # For methods that affect nothing, it's OK to set movable to our
                # notion of infallible on the C++ side, without considering
                # argument conversions, since argument conversions that can
                # reliably throw would be effectful anyway and the jit doesn't
                # move effectful things.
                extendedAttrs = self.descriptor.getExtendedAttributes(self.member)
                hasInfallibleImpl = "needsErrorResult" not in extendedAttrs
                # At this point hasInfallibleImpl is true if our method either
                # can't throw at all, or can only throw OOM.  In both cases, it
                # may be safe to move, or dead-code-eliminate, the method,
                # because throwing OOM is not semantically meaningful, so code
                # can't rely on it happening.  Note that this makes the behavior
                # consistent for OOM thrown from the method itself and OOM
                # thrown from the to-JS conversion of the return value (see the
                # "canOOM" and "infallibleForMember" checks below).
                movable = self.mayBeMovable() and hasInfallibleImpl
                eliminatable = self.mayBeEliminatable() and hasInfallibleImpl
                # XXXbz can we move the smarts about fallibility due to arg
                # conversions into the JIT, using our new args stuff?
                if len(sig[1]) != 0 or not infallibleForMember(
                    self.member, sig[0], self.descriptor
                ):
                    # We have arguments or our return-value boxing can fail
                    methodInfal = False
                else:
                    methodInfal = hasInfallibleImpl and "canOOM" not in extendedAttrs
                # For now, only bother to output args if we're side-effect-free.
                if self.member.affects == "Nothing":
                    args = sig[1]
                else:
                    args = None

            aliasSet = self.aliasSet()
            result = self.defineJitInfo(
                methodinfo,
                method,
                "Method",
                methodInfal,
                movable,
                eliminatable,
                aliasSet,
                False,
                False,
                None,
                [s[0] for s in sigs],
                args,
            )
            return result
        raise TypeError("Illegal member type to CGPropertyJITInfo")

    def mayBeMovable(self):
        """
        Returns whether this attribute or method may be movable, just
        based on Affects/DependsOn annotations.
        """
        affects = self.member.affects
        dependsOn = self.member.dependsOn
        assert affects in IDLInterfaceMember.AffectsValues
        assert dependsOn in IDLInterfaceMember.DependsOnValues
        # Things that are DependsOn=DeviceState are not movable, because we
        # don't want them coalesced with each other or loop-hoisted, since
        # their return value can change even if nothing is going on from our
        # point of view.
        return affects == "Nothing" and (
            dependsOn != "Everything" and dependsOn != "DeviceState"
        )

    def mayBeEliminatable(self):
        """
        Returns whether this attribute or method may be eliminatable, just
        based on Affects/DependsOn annotations.
        """
        # dependsOn shouldn't affect this decision at all, except in jitinfo we
        # have no way to express "Depends on everything, affects nothing",
        # because we only have three alias set values: AliasNone ("depends on
        # nothing, affects nothing"), AliasDOMSets ("depends on DOM sets,
        # affects nothing"), AliasEverything ("depends on everything, affects
        # everything").  So the [Affects=Nothing, DependsOn=Everything] case
        # gets encoded as AliasEverything and defineJitInfo asserts that if our
        # alias state is AliasEverything then we're not eliminatable (because it
        # thinks we might have side-effects at that point).  Bug 1155796 is
        # tracking possible solutions for this.
        affects = self.member.affects
        dependsOn = self.member.dependsOn
        assert affects in IDLInterfaceMember.AffectsValues
        assert dependsOn in IDLInterfaceMember.DependsOnValues
        return affects == "Nothing" and dependsOn != "Everything"

    def aliasSet(self):
        """
        Returns the alias set to store in the jitinfo.  This may not be the
        effective alias set the JIT uses, depending on whether we have enough
        information about our args to allow the JIT to prove that effectful
        argument conversions won't happen.
        """
        dependsOn = self.member.dependsOn
        assert dependsOn in IDLInterfaceMember.DependsOnValues

        if dependsOn == "Nothing" or dependsOn == "DeviceState":
            assert self.member.affects == "Nothing"
            return "AliasNone"

        if dependsOn == "DOMState":
            assert self.member.affects == "Nothing"
            return "AliasDOMSets"

        return "AliasEverything"

    @staticmethod
    def getJSReturnTypeTag(t):
        if t.nullable():
            # Sometimes it might return null, sometimes not
            return "JSVAL_TYPE_UNKNOWN"
        if t.isUndefined():
            # No return, every time
            return "JSVAL_TYPE_UNDEFINED"
        if t.isSequence():
            return "JSVAL_TYPE_OBJECT"
        if t.isRecord():
            return "JSVAL_TYPE_OBJECT"
        if t.isPromise():
            return "JSVAL_TYPE_OBJECT"
        if t.isGeckoInterface():
            return "JSVAL_TYPE_OBJECT"
        if t.isString():
            return "JSVAL_TYPE_STRING"
        if t.isEnum():
            return "JSVAL_TYPE_STRING"
        if t.isCallback():
            return "JSVAL_TYPE_OBJECT"
        if t.isAny():
            # The whole point is to return various stuff
            return "JSVAL_TYPE_UNKNOWN"
        if t.isObject():
            return "JSVAL_TYPE_OBJECT"
        if t.isSpiderMonkeyInterface():
            return "JSVAL_TYPE_OBJECT"
        if t.isUnion():
            u = t.unroll()
            if u.hasNullableType:
                # Might be null or not
                return "JSVAL_TYPE_UNKNOWN"
            return functools.reduce(
                CGMemberJITInfo.getSingleReturnType, u.flatMemberTypes, ""
            )
        if t.isDictionary():
            return "JSVAL_TYPE_OBJECT"
        if t.isObservableArray():
            return "JSVAL_TYPE_OBJECT"
        if not t.isPrimitive():
            raise TypeError("No idea what type " + str(t) + " is.")
        tag = t.tag()
        if tag == IDLType.Tags.bool:
            return "JSVAL_TYPE_BOOLEAN"
        if tag in [
            IDLType.Tags.int8,
            IDLType.Tags.uint8,
            IDLType.Tags.int16,
            IDLType.Tags.uint16,
            IDLType.Tags.int32,
        ]:
            return "JSVAL_TYPE_INT32"
        if tag in [
            IDLType.Tags.int64,
            IDLType.Tags.uint64,
            IDLType.Tags.unrestricted_float,
            IDLType.Tags.float,
            IDLType.Tags.unrestricted_double,
            IDLType.Tags.double,
        ]:
            # These all use JS_NumberValue, which can return int or double.
            # But TI treats "double" as meaning "int or double", so we're
            # good to return JSVAL_TYPE_DOUBLE here.
            return "JSVAL_TYPE_DOUBLE"
        if tag != IDLType.Tags.uint32:
            raise TypeError("No idea what type " + str(t) + " is.")
        # uint32 is sometimes int and sometimes double.
        return "JSVAL_TYPE_DOUBLE"

    @staticmethod
    def getSingleReturnType(existingType, t):
        type = CGMemberJITInfo.getJSReturnTypeTag(t)
        if existingType == "":
            # First element of the list; just return its type
            return type

        if type == existingType:
            return existingType
        if (type == "JSVAL_TYPE_DOUBLE" and existingType == "JSVAL_TYPE_INT32") or (
            existingType == "JSVAL_TYPE_DOUBLE" and type == "JSVAL_TYPE_INT32"
        ):
            # Promote INT32 to DOUBLE as needed
            return "JSVAL_TYPE_DOUBLE"
        # Different types
        return "JSVAL_TYPE_UNKNOWN"

    @staticmethod
    def getJSArgType(t):
        assert not t.isUndefined()
        if t.nullable():
            # Sometimes it might return null, sometimes not
            return (
                "JSJitInfo::ArgType(JSJitInfo::Null | %s)"
                % CGMemberJITInfo.getJSArgType(t.inner)
            )
        if t.isSequence():
            return "JSJitInfo::Object"
        if t.isPromise():
            return "JSJitInfo::Object"
        if t.isGeckoInterface():
            return "JSJitInfo::Object"
        if t.isString():
            return "JSJitInfo::String"
        if t.isEnum():
            return "JSJitInfo::String"
        if t.isCallback():
            return "JSJitInfo::Object"
        if t.isAny():
            # The whole point is to return various stuff
            return "JSJitInfo::Any"
        if t.isObject():
            return "JSJitInfo::Object"
        if t.isSpiderMonkeyInterface():
            return "JSJitInfo::Object"
        if t.isUnion():
            u = t.unroll()
            type = "JSJitInfo::Null" if u.hasNullableType else ""
            return "JSJitInfo::ArgType(%s)" % functools.reduce(
                CGMemberJITInfo.getSingleArgType, u.flatMemberTypes, type
            )
        if t.isDictionary():
            return "JSJitInfo::Object"
        if not t.isPrimitive():
            raise TypeError("No idea what type " + str(t) + " is.")
        tag = t.tag()
        if tag == IDLType.Tags.bool:
            return "JSJitInfo::Boolean"
        if tag in [
            IDLType.Tags.int8,
            IDLType.Tags.uint8,
            IDLType.Tags.int16,
            IDLType.Tags.uint16,
            IDLType.Tags.int32,
        ]:
            return "JSJitInfo::Integer"
        if tag in [
            IDLType.Tags.int64,
            IDLType.Tags.uint64,
            IDLType.Tags.unrestricted_float,
            IDLType.Tags.float,
            IDLType.Tags.unrestricted_double,
            IDLType.Tags.double,
        ]:
            # These all use JS_NumberValue, which can return int or double.
            # But TI treats "double" as meaning "int or double", so we're
            # good to return JSVAL_TYPE_DOUBLE here.
            return "JSJitInfo::Double"
        if tag != IDLType.Tags.uint32:
            raise TypeError("No idea what type " + str(t) + " is.")
        # uint32 is sometimes int and sometimes double.
        return "JSJitInfo::Double"

    @staticmethod
    def getSingleArgType(existingType, t):
        type = CGMemberJITInfo.getJSArgType(t)
        if existingType == "":
            # First element of the list; just return its type
            return type

        if type == existingType:
            return existingType
        return "%s | %s" % (existingType, type)


class CGStaticMethodJitinfo(CGGeneric):
    """
    A class for generating the JITInfo for a promise-returning static method.
    """

    def __init__(self, method):
        CGGeneric.__init__(
            self,
            "\n"
            "static const JSJitInfo %s_methodinfo = {\n"
            "  { (JSJitGetterOp)%s },\n"
            "  { prototypes::id::_ID_Count }, { 0 }, JSJitInfo::StaticMethod,\n"
            "  JSJitInfo::AliasEverything, JSVAL_TYPE_OBJECT, false, false,\n"
            "  false, false, 0\n"
            "};\n"
            % (
                IDLToCIdentifier(method.identifier.name),
                CppKeywords.checkMethodName(IDLToCIdentifier(method.identifier.name)),
            ),
        )


def getEnumValueName(value):
    # Some enum values can be empty strings.  Others might have weird
    # characters in them.  Deal with the former by returning "_empty",
    # deal with possible name collisions from that by throwing if the
    # enum value is actually "_empty", and throw on any value
    # containing non-ASCII chars for now. Replace all chars other than
    # [0-9A-Za-z_] with '_'.
    if re.match("[^\x20-\x7E]", value):
        raise SyntaxError('Enum value "' + value + '" contains non-ASCII characters')
    if re.match("^[0-9]", value):
        value = "_" + value
    value = re.sub(r"[^0-9A-Za-z_]", "_", value)
    if re.match("^_[A-Z]|__", value):
        raise SyntaxError('Enum value "' + value + '" is reserved by the C++ spec')
    if value == "_empty":
        raise SyntaxError('"_empty" is not an IDL enum value we support yet')
    if value == "":
        return "_empty"
    return MakeNativeName(value)


class CGEnumToJSValue(CGAbstractMethod):
    def __init__(self, enum):
        enumType = enum.identifier.name
        self.stringsArray = "binding_detail::EnumStrings<" + enumType + ">::Values"
        CGAbstractMethod.__init__(
            self,
            None,
            "ToJSValue",
            "bool",
            [
                Argument("JSContext*", "aCx"),
                Argument(enumType, "aArgument"),
                Argument("JS::MutableHandle<JS::Value>", "aValue"),
            ],
        )

    def definition_body(self):
        return fill(
            """
            MOZ_ASSERT(uint32_t(aArgument) < std::size(${strings}));
            JSString* resultStr =
              JS_NewStringCopyN(aCx, ${strings}[uint32_t(aArgument)].BeginReading(),
                                ${strings}[uint32_t(aArgument)].Length());
            if (!resultStr) {
              return false;
            }
            aValue.setString(resultStr);
            return true;
            """,
            strings=self.stringsArray,
        )


class CGEnum(CGThing):
    def __init__(self, enum):
        CGThing.__init__(self)
        self.enum = enum
        strings = CGNamespace(
            "binding_detail",
            CGGeneric(
                declare=fill(
                    """
                    template <> struct EnumStrings<${name}> {
                      static constexpr nsLiteralCString Values[${count}] {
                        $*{entries}
                      };
                    };
                    """,
                    name=self.enum.identifier.name,
                    count=self.nEnumStrings(),
                    entries="".join('"%s"_ns,\n' % val for val in self.enum.values()),
                ),
                define=fill(
                    """
                    constexpr nsLiteralCString EnumStrings<${name}>::Values[${count}];
                    """,
                    name=self.enum.identifier.name,
                    count=self.nEnumStrings(),
                ),
            ),
        )
        toJSValue = CGEnumToJSValue(enum)
        self.cgThings = CGList([strings, toJSValue], "\n")

    def nEnumStrings(self):
        return len(self.enum.values())

    @staticmethod
    def underlyingType(enum):
        count = len(enum.values())
        if count <= 256:
            return "uint8_t"
        if count <= 65536:
            return "uint16_t"
        raise ValueError("Enum " + enum.identifier.name + " has more than 65536 values")

    def declare(self):
        decl = fill(
            """
            enum class ${name} : ${ty} {
              $*{enums}
            };
            """,
            name=self.enum.identifier.name,
            ty=CGEnum.underlyingType(self.enum),
            enums=",\n".join(map(getEnumValueName, self.enum.values())) + ",\n",
        )

        return decl + "\n" + self.cgThings.declare()

    def define(self):
        return self.cgThings.define()

    def deps(self):
        return self.enum.getDeps()


class CGMaxContiguousEnumValue(CGThing):
    def __init__(self, enum):
        CGThing.__init__(self)
        self.enum = enum

    def declare(self):
        enumValues = self.enum.values()
        return fill(
            """
            template <>
            struct MaxContiguousEnumValue<dom::${name}>
            {
              static constexpr dom::${name} value = dom::${name}::${maxValue};

              static_assert(static_cast<${ty}>(dom::${name}::${minValue}) == 0,
                            "We rely on this in ContiguousEnumValues");
              static_assert(std::size(dom::binding_detail::EnumStrings<dom::${name}>::Values) - 1 == UnderlyingValue(value),
                            "Mismatch between enum strings and enum count");
            };
            """,
            name=self.enum.identifier.name,
            ty=CGEnum.underlyingType(self.enum),
            maxValue=getEnumValueName(enumValues[-1]),
            minValue=getEnumValueName(enumValues[0]),
        )

    def define(self):
        return ""

    def deps(self):
        return self.enum.getDeps()


def getUnionAccessorSignatureType(type, descriptorProvider):
    """
    Returns the types that are used in the getter and setter signatures for
    union types
    """
    # Flat member types have already unwrapped nullables.
    assert not type.nullable()

    # Promise types can never appear in unions, because Promise is not
    # distinguishable from anything.
    assert not type.isPromise()

    if type.isSequence() or type.isRecord():
        if type.isSequence():
            wrapperType = "Sequence"
        else:
            wrapperType = "Record"
        # We don't use the returned template here, so it's OK to just pass no
        # sourceDescription.
        elementInfo = getJSToNativeConversionInfo(
            type.inner, descriptorProvider, isMember=wrapperType
        )
        if wrapperType == "Sequence":
            innerType = elementInfo.declType
        else:
            innerType = [recordKeyDeclType(type), elementInfo.declType]

        return CGTemplatedType(wrapperType, innerType, isConst=True, isReference=True)

    # Nested unions are unwrapped automatically into our flatMemberTypes.
    assert not type.isUnion()

    if type.isGeckoInterface():
        descriptor = descriptorProvider.getDescriptor(
            type.unroll().inner.identifier.name
        )
        typeName = CGGeneric(descriptor.nativeType)
        if not type.unroll().inner.isExternal():
            typeName = CGWrapper(typeName, post="&")
        elif descriptor.interface.identifier.name == "WindowProxy":
            typeName = CGGeneric("WindowProxyHolder const&")
        else:
            # Allow null pointers for old-binding classes.
            typeName = CGWrapper(typeName, post="*")
        return typeName

    if type.isSpiderMonkeyInterface():
        typeName = CGGeneric(type.name)
        return CGWrapper(typeName, post=" const &")

    if type.isJSString():
        raise TypeError("JSString not supported in unions")

    if type.isDOMString() or type.isUSVString():
        return CGGeneric("const nsAString&")

    if type.isUTF8String():
        return CGGeneric("const nsACString&")

    if type.isByteString():
        return CGGeneric("const nsCString&")

    if type.isEnum():
        return CGGeneric(type.inner.identifier.name)

    if type.isCallback():
        return CGGeneric("%s&" % type.unroll().callback.identifier.name)

    if type.isAny():
        return CGGeneric("JS::Value")

    if type.isObject():
        return CGGeneric("JSObject*")

    if type.isDictionary():
        return CGGeneric("const %s&" % type.inner.identifier.name)

    if not type.isPrimitive():
        raise TypeError("Need native type for argument type '%s'" % str(type))

    return CGGeneric(builtinNames[type.tag()])


def getUnionTypeTemplateVars(unionType, type, descriptorProvider, isMember=False):
    assert not type.isUndefined()
    assert not isMember or isMember in ("Union", "OwningUnion")

    ownsMembers = isMember == "OwningUnion"
    name = getUnionMemberName(type)
    holderName = "m" + name + "Holder"

    # By the time tryNextCode is invoked, we're guaranteed the union has been
    # constructed as some type, since we've been trying to convert into the
    # corresponding member.
    tryNextCode = fill(
        """
        Destroy${name}();
        tryNext = true;
        return true;
        """,
        name=name,
    )

    sourceDescription = "%s branch of %s" % (type.prettyName(), unionType.prettyName())

    conversionInfo = getJSToNativeConversionInfo(
        type,
        descriptorProvider,
        failureCode=tryNextCode,
        isDefinitelyObject=not type.isDictionary(),
        isMember=isMember,
        sourceDescription=sourceDescription,
    )

    ctorNeedsCx = conversionInfo.declArgs == "cx"
    ctorArgs = "cx" if ctorNeedsCx else ""

    structType = conversionInfo.declType.define()
    externalType = getUnionAccessorSignatureType(type, descriptorProvider).define()

    if type.isObject():
        if ownsMembers:
            setValue = "mValue.mObject.SetValue(obj);"
        else:
            setValue = "mValue.mObject.SetValue(cx, obj);"

        body = fill(
            """
            MOZ_ASSERT(mType == eUninitialized);
            ${setValue}
            mType = eObject;
            """,
            setValue=setValue,
        )

        # It's a bit sketchy to do the security check after setting the value,
        # but it keeps the code cleaner and lets us avoid rooting |obj| over the
        # call to CallerSubsumes().
        body = body + fill(
            """
            if (passedToJSImpl && !CallerSubsumes(obj)) {
              cx.ThrowErrorMessage<MSG_PERMISSION_DENIED_TO_PASS_ARG>("${sourceDescription}");
              return false;
            }
            return true;
            """,
            sourceDescription=sourceDescription,
        )

        setters = [
            ClassMethod(
                "SetToObject",
                "bool",
                [
                    Argument("BindingCallContext&", "cx"),
                    Argument("JSObject*", "obj"),
                    Argument("bool", "passedToJSImpl", default="false"),
                ],
                inline=True,
                bodyInHeader=True,
                body=body,
            )
        ]
    elif type.isDictionary() and not type.inner.needsConversionFromJS:
        # In this case we are never initialized from JS to start with
        setters = None
    else:
        # Important: we need to not have our declName involve
        # maybe-GCing operations.
        jsConversion = fill(
            conversionInfo.template,
            val="value",
            maybeMutableVal="value",
            declName="memberSlot",
            holderName=(holderName if ownsMembers else "%s.ref()" % holderName),
            passedToJSImpl="passedToJSImpl",
        )

        jsConversion = fill(
            """
            tryNext = false;
            { // scope for memberSlot
              ${structType}& memberSlot = RawSetAs${name}(${ctorArgs});
              $*{jsConversion}
            }
            return true;
            """,
            structType=structType,
            name=name,
            ctorArgs=ctorArgs,
            jsConversion=jsConversion,
        )

        needCallContext = idlTypeNeedsCallContext(type)
        if needCallContext:
            cxType = "BindingCallContext&"
        else:
            cxType = "JSContext*"
        setters = [
            ClassMethod(
                "TrySetTo" + name,
                "bool",
                [
                    Argument(cxType, "cx"),
                    Argument("JS::Handle<JS::Value>", "value"),
                    Argument("bool&", "tryNext"),
                    Argument("bool", "passedToJSImpl", default="false"),
                ],
                visibility="private",
                body=jsConversion,
            )
        ]
        if needCallContext:
            # Add a method for non-binding uses of unions to allow them to set
            # things in the union without providing a call context (though if
            # they want good error reporting they'll provide one anyway).
            shimBody = fill(
                """
                BindingCallContext cx(cx_, nullptr);
                return TrySetTo${name}(cx, value, tryNext, passedToJSImpl);
                """,
                name=name,
            )
            setters.append(
                ClassMethod(
                    "TrySetTo" + name,
                    "bool",
                    [
                        Argument("JSContext*", "cx_"),
                        Argument("JS::Handle<JS::Value>", "value"),
                        Argument("bool&", "tryNext"),
                        Argument("bool", "passedToJSImpl", default="false"),
                    ],
                    visibility="private",
                    body=shimBody,
                )
            )

    return {
        "name": name,
        "structType": structType,
        "externalType": externalType,
        "setters": setters,
        "ctorArgs": ctorArgs,
        "ctorArgList": [Argument("JSContext*", "cx")] if ctorNeedsCx else [],
    }


def getUnionConversionTemplate(type):
    assert type.isUnion()
    assert not type.nullable()

    memberTypes = type.flatMemberTypes
    prettyNames = []

    interfaceMemberTypes = [t for t in memberTypes if t.isNonCallbackInterface()]
    if len(interfaceMemberTypes) > 0:
        interfaceObject = []
        for memberType in interfaceMemberTypes:
            name = getUnionMemberName(memberType)
            interfaceObject.append(
                CGGeneric(
                    "(failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext"
                    % name
                )
            )
            prettyNames.append(memberType.prettyName())
        interfaceObject = CGWrapper(
            CGList(interfaceObject, " ||\n"),
            pre="done = ",
            post=";\n",
            reindent=True,
        )
    else:
        interfaceObject = None

    sequenceObjectMemberTypes = [t for t in memberTypes if t.isSequence()]
    if len(sequenceObjectMemberTypes) > 0:
        assert len(sequenceObjectMemberTypes) == 1
        memberType = sequenceObjectMemberTypes[0]
        name = getUnionMemberName(memberType)
        sequenceObject = CGGeneric(
            "done = (failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n"
            % name
        )
        prettyNames.append(memberType.prettyName())
    else:
        sequenceObject = None

    callbackMemberTypes = [
        t for t in memberTypes if t.isCallback() or t.isCallbackInterface()
    ]
    if len(callbackMemberTypes) > 0:
        assert len(callbackMemberTypes) == 1
        memberType = callbackMemberTypes[0]
        name = getUnionMemberName(memberType)
        callbackObject = CGGeneric(
            "done = (failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n"
            % name
        )
        prettyNames.append(memberType.prettyName())
    else:
        callbackObject = None

    dictionaryMemberTypes = [t for t in memberTypes if t.isDictionary()]
    if len(dictionaryMemberTypes) > 0:
        assert len(dictionaryMemberTypes) == 1
        memberType = dictionaryMemberTypes[0]
        name = getUnionMemberName(memberType)
        setDictionary = CGGeneric(
            "done = (failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n"
            % name
        )
        prettyNames.append(memberType.prettyName())
    else:
        setDictionary = None

    recordMemberTypes = [t for t in memberTypes if t.isRecord()]
    if len(recordMemberTypes) > 0:
        assert len(recordMemberTypes) == 1
        memberType = recordMemberTypes[0]
        name = getUnionMemberName(memberType)
        recordObject = CGGeneric(
            "done = (failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n"
            % name
        )
        prettyNames.append(memberType.prettyName())
    else:
        recordObject = None

    objectMemberTypes = [t for t in memberTypes if t.isObject()]
    if len(objectMemberTypes) > 0:
        assert len(objectMemberTypes) == 1
        # Very important to NOT construct a temporary Rooted here, since the
        # SetToObject call can call a Rooted constructor and we need to keep
        # stack discipline for Rooted.
        object = CGGeneric(
            "if (!SetToObject(cx, &${val}.toObject(), ${passedToJSImpl})) {\n"
            "  return false;\n"
            "}\n"
            "done = true;\n"
        )
        prettyNames.append(objectMemberTypes[0].prettyName())
    else:
        object = None

    hasObjectTypes = (
        interfaceObject or sequenceObject or callbackObject or object or recordObject
    )
    if hasObjectTypes:
        # "object" is not distinguishable from other types
        assert not object or not (
            interfaceObject or sequenceObject or callbackObject or recordObject
        )
        if sequenceObject or callbackObject:
            # An object can be both an sequence object and a callback or
            # dictionary, but we shouldn't have both in the union's members
            # because they are not distinguishable.
            assert not (sequenceObject and callbackObject)
            templateBody = CGElseChain([sequenceObject, callbackObject])
        else:
            templateBody = None
        if interfaceObject:
            assert not object
            if templateBody:
                templateBody = CGIfWrapper(templateBody, "!done")
            templateBody = CGList([interfaceObject, templateBody])
        else:
            templateBody = CGList([templateBody, object])

        if recordObject:
            templateBody = CGList([templateBody, CGIfWrapper(recordObject, "!done")])

        templateBody = CGIfWrapper(templateBody, "${val}.isObject()")
    else:
        templateBody = CGGeneric()

    if setDictionary:
        assert not object
        templateBody = CGList([templateBody, CGIfWrapper(setDictionary, "!done")])

    stringTypes = [t for t in memberTypes if t.isString() or t.isEnum()]
    numericTypes = [t for t in memberTypes if t.isNumeric()]
    booleanTypes = [t for t in memberTypes if t.isBoolean()]
    if stringTypes or numericTypes or booleanTypes:
        assert len(stringTypes) <= 1
        assert len(numericTypes) <= 1
        assert len(booleanTypes) <= 1

        # We will wrap all this stuff in a do { } while (0); so we
        # can use "break" for flow control.
        def getStringOrPrimitiveConversion(memberType):
            name = getUnionMemberName(memberType)
            return CGGeneric(
                "done = (failed = !TrySetTo%s(cx, ${val}, tryNext)) || !tryNext;\n"
                "break;\n" % name
            )

        other = CGList([])
        stringConversion = [getStringOrPrimitiveConversion(t) for t in stringTypes]
        numericConversion = [getStringOrPrimitiveConversion(t) for t in numericTypes]
        booleanConversion = [getStringOrPrimitiveConversion(t) for t in booleanTypes]
        if stringConversion:
            if booleanConversion:
                other.append(CGIfWrapper(booleanConversion[0], "${val}.isBoolean()"))
            if numericConversion:
                other.append(CGIfWrapper(numericConversion[0], "${val}.isNumber()"))
            other.append(stringConversion[0])
        elif numericConversion:
            if booleanConversion:
                other.append(CGIfWrapper(booleanConversion[0], "${val}.isBoolean()"))
            other.append(numericConversion[0])
        else:
            assert booleanConversion
            other.append(booleanConversion[0])

        other = CGWrapper(CGIndenter(other), pre="do {\n", post="} while (false);\n")
        if hasObjectTypes or setDictionary:
            other = CGWrapper(CGIndenter(other), "{\n", post="}\n")
            if object:
                templateBody = CGElseChain([templateBody, other])
            else:
                other = CGWrapper(other, pre="if (!done) ")
                templateBody = CGList([templateBody, other])
        else:
            assert templateBody.define() == ""
            templateBody = other
    else:
        other = None

    templateBody = CGWrapper(
        templateBody, pre="bool done = false, failed = false, tryNext;\n"
    )
    throw = CGGeneric(
        fill(
            """
            if (failed) {
              return false;
            }
            if (!done) {
              cx.ThrowErrorMessage<MSG_NOT_IN_UNION>(sourceDescription, "${names}");
              return false;
            }
            """,
            names=", ".join(prettyNames),
        )
    )

    templateBody = CGList([templateBody, throw])

    hasUndefinedType = any(t.isUndefined() for t in memberTypes)
    elseChain = []

    # The spec does this before anything else, but we do it after checking
    # for null in the case of a nullable union. In practice this shouldn't
    # make a difference, but it makes things easier because we first need to
    # call Construct on our Maybe<...>, before we can set the union type to
    # undefined, and we do that below after checking for null (see the
    # 'if nullable:' block below).
    if hasUndefinedType:
        elseChain.append(
            CGIfWrapper(
                CGGeneric("SetUndefined();\n"),
                "${val}.isUndefined()",
            )
        )

    if type.hasNullableType:
        nullTest = (
            "${val}.isNull()" if hasUndefinedType else "${val}.isNullOrUndefined()"
        )
        elseChain.append(
            CGIfWrapper(
                CGGeneric("SetNull();\n"),
                nullTest,
            )
        )

    if len(elseChain) > 0:
        elseChain.append(CGWrapper(CGIndenter(templateBody), pre="{\n", post="}\n"))
        templateBody = CGElseChain(elseChain)

    return templateBody


def getUnionInitMethods(type, isOwningUnion=False):
    assert type.isUnion()

    template = getUnionConversionTemplate(type).define()

    replacements = {
        "val": "value",
        "passedToJSImpl": "passedToJSImpl",
    }

    initBody = fill(
        """
        MOZ_ASSERT(mType == eUninitialized);

        $*{conversion}
        return true;
        """,
        conversion=string.Template(template).substitute(replacements),
    )

    return [
        ClassMethod(
            "Init",
            "bool",
            [
                Argument("BindingCallContext&", "cx"),
                Argument("JS::Handle<JS::Value>", "value"),
                Argument("const char*", "sourceDescription", default='"Value"'),
                Argument("bool", "passedToJSImpl", default="false"),
            ],
            visibility="public",
            body=initBody,
        ),
        ClassMethod(
            "Init",
            "bool",
            [
                Argument("JSContext*", "cx_"),
                Argument("JS::Handle<JS::Value>", "value"),
                Argument("const char*", "sourceDescription", default='"Value"'),
                Argument("bool", "passedToJSImpl", default="false"),
            ],
            visibility="public",
            body=dedent(
                """
                BindingCallContext cx(cx_, nullptr);
                return Init(cx, value, sourceDescription, passedToJSImpl);
                """
            ),
        ),
    ]


class CGUnionStruct(CGThing):
    def __init__(self, type, descriptorProvider, ownsMembers=False):
        CGThing.__init__(self)
        self.type = type.unroll()
        self.descriptorProvider = descriptorProvider
        self.ownsMembers = ownsMembers
        self.struct = self.getStruct()

    def declare(self):
        return self.struct.declare()

    def define(self):
        return self.struct.define()

    def deps(self):
        return self.type.getDeps()

    def getStruct(self):
        members = [
            ClassMember("mType", "TypeOrUninit", body="eUninitialized"),
            ClassMember("mValue", "Value"),
        ]
        ctor = ClassConstructor(
            [], bodyInHeader=True, visibility="public", explicit=True
        )

        methods = []
        enumValues = ["eUninitialized"]
        toJSValCases = [
            CGCase(
                "eUninitialized", CGGeneric("return false;\n"), CGCase.DONT_ADD_BREAK
            )
        ]
        destructorCases = [CGCase("eUninitialized", None)]
        assignmentCase = CGCase(
            "eUninitialized",
            CGGeneric(
                "MOZ_ASSERT(mType == eUninitialized,\n"
                '           "We need to destroy ourselves?");\n'
            ),
        )
        assignmentCases = [assignmentCase]
        moveCases = [assignmentCase]
        traceCases = []
        unionValues = []

        def addSpecialType(typename):
            enumValue = "e" + typename
            enumValues.append(enumValue)
            methods.append(
                ClassMethod(
                    "Is" + typename,
                    "bool",
                    [],
                    const=True,
                    inline=True,
                    body="return mType == %s;\n" % enumValue,
                    bodyInHeader=True,
                )
            )
            methods.append(
                ClassMethod(
                    "Set" + typename,
                    "void",
                    [],
                    inline=True,
                    body=fill(
                        """
                        Uninit();
                        mType = ${enumValue};
                        """,
                        enumValue=enumValue,
                    ),
                    bodyInHeader=True,
                )
            )
            destructorCases.append(CGCase(enumValue, None))
            assignmentCase = CGCase(
                enumValue,
                CGGeneric(
                    fill(
                        """
                            MOZ_ASSERT(mType == eUninitialized);
                            mType = ${enumValue};
                            """,
                        enumValue=enumValue,
                    )
                ),
            )
            assignmentCases.append(assignmentCase)
            moveCases.append(assignmentCase)
            toJSValCases.append(
                CGCase(
                    enumValue,
                    CGGeneric(
                        fill(
                            """
                            rval.set${typename}();
                            return true;
                            """,
                            typename=typename,
                        )
                    ),
                    CGCase.DONT_ADD_BREAK,
                )
            )

        if self.type.hasNullableType:
            addSpecialType("Null")

        hasObjectType = any(t.isObject() for t in self.type.flatMemberTypes)
        skipToJSVal = False
        for t in self.type.flatMemberTypes:
            if t.isUndefined():
                addSpecialType("Undefined")
                continue

            vars = getUnionTypeTemplateVars(
                self.type,
                t,
                self.descriptorProvider,
                isMember="OwningUnion" if self.ownsMembers else "Union",
            )
            if vars["setters"]:
                methods.extend(vars["setters"])
            uninit = "Uninit();"
            if hasObjectType and not self.ownsMembers:
                uninit = (
                    'MOZ_ASSERT(mType != eObject, "This will not play well with Rooted");\n'
                    + uninit
                )
            if not t.isObject() or self.ownsMembers:
                body = fill(
                    """
                    if (mType == e${name}) {
                      return mValue.m${name}.Value();
                    }
                    %s
                    mType = e${name};
                    return mValue.m${name}.SetValue(${ctorArgs});
                    """,
                    **vars,
                )

                # bodyInHeader must be false for return values because they own
                # their union members and we don't want include headers in
                # UnionTypes.h just to call Addref/Release
                methods.append(
                    ClassMethod(
                        "RawSetAs" + vars["name"],
                        vars["structType"] + "&",
                        vars["ctorArgList"],
                        bodyInHeader=not self.ownsMembers,
                        body=body % "MOZ_ASSERT(mType == eUninitialized);",
                        noDiscard=True,
                    )
                )
                methods.append(
                    ClassMethod(
                        "SetAs" + vars["name"],
                        vars["structType"] + "&",
                        vars["ctorArgList"],
                        bodyInHeader=not self.ownsMembers,
                        body=body % uninit,
                        noDiscard=True,
                    )
                )

                # Provide a SetStringLiteral() method to support string defaults.
                if t.isByteString() or t.isUTF8String():
                    charType = "const nsCString::char_type"
                elif t.isString():
                    charType = "const nsString::char_type"
                else:
                    charType = None

                if charType:
                    methods.append(
                        ClassMethod(
                            "SetStringLiteral",
                            "void",
                            # Hack, but it works...
                            [Argument(charType, "(&aData)[N]")],
                            inline=True,
                            bodyInHeader=True,
                            templateArgs=["int N"],
                            body="RawSetAs%s().AssignLiteral(aData);\n" % t.name,
                        )
                    )

            body = fill("return mType == e${name};\n", **vars)
            methods.append(
                ClassMethod(
                    "Is" + vars["name"],
                    "bool",
                    [],
                    const=True,
                    bodyInHeader=True,
                    body=body,
                )
            )

            body = fill(
                """
                MOZ_RELEASE_ASSERT(Is${name}(), "Wrong type!");
                mValue.m${name}.Destroy();
                mType = eUninitialized;
                """,
                **vars,
            )
            methods.append(
                ClassMethod(
                    "Destroy" + vars["name"],
                    "void",
                    [],
                    visibility="private",
                    bodyInHeader=not self.ownsMembers,
                    body=body,
                )
            )

            body = fill(
                """
                MOZ_RELEASE_ASSERT(Is${name}(), "Wrong type!");
                return mValue.m${name}.Value();
                """,
                **vars,
            )
            # The non-const version of GetAs* returns our internal type
            getterReturnType = "%s&" % vars["structType"]
            methods.append(
                ClassMethod(
                    "GetAs" + vars["name"],
                    getterReturnType,
                    [],
                    bodyInHeader=True,
                    body=body,
                )
            )
            # The const version of GetAs* returns our internal type
            # for owning unions, but our external type for non-owning
            # ones.
            if self.ownsMembers:
                getterReturnType = "%s const &" % vars["structType"]
            else:
                getterReturnType = vars["externalType"]
            methods.append(
                ClassMethod(
                    "GetAs" + vars["name"],
                    getterReturnType,
                    [],
                    const=True,
                    bodyInHeader=True,
                    body=body,
                )
            )

            unionValues.append(fill("UnionMember<${structType} > m${name}", **vars))
            destructorCases.append(
                CGCase("e" + vars["name"], CGGeneric("Destroy%s();\n" % vars["name"]))
            )

            enumValues.append("e" + vars["name"])

            conversionToJS = self.getConversionToJS(vars, t)
            if conversionToJS:
                toJSValCases.append(
                    CGCase("e" + vars["name"], conversionToJS, CGCase.DONT_ADD_BREAK)
                )
            else:
                skipToJSVal = True

            assignmentCases.append(
                CGCase(
                    "e" + vars["name"],
                    CGGeneric(
                        "SetAs%s() = aOther.GetAs%s();\n" % (vars["name"], vars["name"])
                    ),
                )
            )
            moveCases.append(
                CGCase(
                    "e" + vars["name"],
                    CGGeneric(
                        "mType = e%s;\n" % vars["name"]
                        + "mValue.m%s.SetValue(std::move(aOther.mValue.m%s.Value()));\n"
                        % (vars["name"], vars["name"])
                    ),
                )
            )
            if self.ownsMembers and typeNeedsRooting(t):
                if t.isObject():
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                'JS::TraceRoot(trc, %s, "%s");\n'
                                % (
                                    "&mValue.m" + vars["name"] + ".Value()",
                                    "mValue.m" + vars["name"],
                                )
                            ),
                        )
                    )
                elif t.isDictionary():
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                "mValue.m%s.Value().TraceDictionary(trc);\n"
                                % vars["name"]
                            ),
                        )
                    )
                elif t.isSequence():
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                "DoTraceSequence(trc, mValue.m%s.Value());\n"
                                % vars["name"]
                            ),
                        )
                    )
                elif t.isRecord():
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                "TraceRecord(trc, mValue.m%s.Value());\n" % vars["name"]
                            ),
                        )
                    )
                else:
                    assert t.isSpiderMonkeyInterface()
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                "mValue.m%s.Value().TraceSelf(trc);\n" % vars["name"]
                            ),
                        )
                    )

        dtor = CGSwitch("mType", destructorCases).define()

        methods.extend(getUnionInitMethods(self.type, isOwningUnion=self.ownsMembers))
        methods.append(
            ClassMethod(
                "Uninit",
                "void",
                [],
                visibility="public",
                body=dtor,
                bodyInHeader=not self.ownsMembers,
                inline=not self.ownsMembers,
            )
        )

        if not skipToJSVal:
            methods.append(
                ClassMethod(
                    "ToJSVal",
                    "bool",
                    [
                        Argument("JSContext*", "cx"),
                        Argument("JS::Handle<JSObject*>", "scopeObj"),
                        Argument("JS::MutableHandle<JS::Value>", "rval"),
                    ],
                    body=CGSwitch(
                        "mType", toJSValCases, default=CGGeneric("return false;\n")
                    ).define(),
                    const=True,
                )
            )

        constructors = [ctor]
        selfName = CGUnionStruct.unionTypeName(self.type, self.ownsMembers)
        if self.ownsMembers:
            if traceCases:
                traceBody = CGSwitch(
                    "mType", traceCases, default=CGGeneric("")
                ).define()
                methods.append(
                    ClassMethod(
                        "TraceUnion",
                        "void",
                        [Argument("JSTracer*", "trc")],
                        body=traceBody,
                    )
                )

            op_body = CGList([])
            op_body.append(CGSwitch("aOther.mType", moveCases))
            constructors.append(
                ClassConstructor(
                    [Argument("%s&&" % selfName, "aOther")],
                    visibility="public",
                    body=op_body.define(),
                )
            )

            methods.append(
                ClassMethod(
                    "operator=",
                    "%s&" % selfName,
                    [Argument("%s&&" % selfName, "aOther")],
                    body="this->~%s();\nnew (this) %s (std::move(aOther));\nreturn *this;\n"
                    % (selfName, selfName),
                )
            )

            body = dedent(
                """
                MOZ_RELEASE_ASSERT(mType != eUninitialized);
                return static_cast<Type>(mType);
                """
            )
            methods.append(
                ClassMethod(
                    "GetType",
                    "Type",
                    [],
                    bodyInHeader=True,
                    body=body,
                    const=True,
                )
            )

            if CGUnionStruct.isUnionCopyConstructible(self.type):
                constructors.append(
                    ClassConstructor(
                        [Argument("const %s&" % selfName, "aOther")],
                        bodyInHeader=True,
                        visibility="public",
                        explicit=True,
                        body="*this = aOther;\n",
                    )
                )
                op_body = CGList([])
                op_body.append(CGSwitch("aOther.mType", assignmentCases))
                op_body.append(CGGeneric("return *this;\n"))
                methods.append(
                    ClassMethod(
                        "operator=",
                        "%s&" % selfName,
                        [Argument("const %s&" % selfName, "aOther")],
                        body=op_body.define(),
                    )
                )
                disallowCopyConstruction = False
            else:
                disallowCopyConstruction = True
        else:
            disallowCopyConstruction = True

        if self.ownsMembers and idlTypeNeedsCycleCollection(self.type):
            friend = (
                "  friend void ImplCycleCollectionUnlink(%s& aUnion);\n"
                % CGUnionStruct.unionTypeName(self.type, True)
            )
        else:
            friend = ""

        enumValuesNoUninit = [x for x in enumValues if x != "eUninitialized"]

        enums = [
            ClassGroup(
                [
                    ClassEnum("TypeOrUninit", enumValues, visibility="private"),
                    ClassEnum(
                        "Type",
                        enumValuesNoUninit,
                        visibility="public",
                        enumClass=True,
                        values=["TypeOrUninit::" + x for x in enumValuesNoUninit],
                    ),
                ]
            )
        ]

        bases = [
            ClassBase("AllOwningUnionBase" if self.ownsMembers else "AllUnionBase")
        ]

        typeAliases = []
        bufferSourceTypes = [
            t.name for t in self.type.flatMemberTypes if t.isBufferSource()
        ]
        if len(bufferSourceTypes) > 0:
            bases.append(ClassBase("UnionWithTypedArraysBase"))
            memberTypesCount = len(self.type.flatMemberTypes)
            if self.type.hasNullableType:
                memberTypesCount += 1

            typeAliases = [
                ClassUsingDeclaration(
                    "ApplyToTypedArrays",
                    "binding_detail::ApplyToTypedArraysHelper<%s, %s, %s>"
                    % (
                        selfName,
                        toStringBool(memberTypesCount > len(bufferSourceTypes)),
                        ", ".join(bufferSourceTypes),
                    ),
                )
            ]

        return CGClass(
            selfName,
            bases=bases,
            typeAliases=typeAliases,
            members=members,
            constructors=constructors,
            methods=methods,
            disallowCopyConstruction=disallowCopyConstruction,
            extradeclarations=friend,
            destructor=ClassDestructor(
                visibility="public", body="Uninit();\n", bodyInHeader=True
            ),
            enums=enums,
            unions=[ClassUnion("Value", unionValues, visibility="private")],
        )

    def getConversionToJS(self, templateVars, type):
        if type.isDictionary() and not type.inner.needsConversionToJS:
            # We won't be able to convert this dictionary to a JS value, nor
            # will we need to, since we don't need a ToJSVal method at all.
            return None

        assert not type.nullable()  # flatMemberTypes never has nullable types
        val = "mValue.m%(name)s.Value()" % templateVars
        wrapCode = wrapForType(
            type,
            self.descriptorProvider,
            {
                "jsvalRef": "rval",
                "jsvalHandle": "rval",
                "obj": "scopeObj",
                "result": val,
                "spiderMonkeyInterfacesAreStructs": True,
            },
        )
        return CGGeneric(wrapCode)

    @staticmethod
    def isUnionCopyConstructible(type):
        return all(isTypeCopyConstructible(t) for t in type.flatMemberTypes)

    @staticmethod
    def unionTypeName(type, ownsMembers):
        """
        Returns a string name for this known union type.
        """
        assert type.isUnion() and not type.nullable()
        return ("Owning" if ownsMembers else "") + type.name

    @staticmethod
    def unionTypeDecl(type, ownsMembers):
        """
        Returns a string for declaring this possibly-nullable union type.
        """
        assert type.isUnion()
        nullable = type.nullable()
        if nullable:
            type = type.inner
        decl = CGGeneric(CGUnionStruct.unionTypeName(type, ownsMembers))
        if nullable:
            decl = CGTemplatedType("Nullable", decl)
        return decl.define()


class ClassItem:
    """Use with CGClass"""

    def __init__(self, name, visibility):
        self.name = name
        self.visibility = visibility

    def declare(self, cgClass):
        assert False

    def define(self, cgClass):
        assert False


class ClassBase(ClassItem):
    def __init__(self, name, visibility="public"):
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        return "%s %s" % (self.visibility, self.name)

    def define(self, cgClass):
        # Only in the header
        return ""


class ClassMethod(ClassItem):
    def __init__(
        self,
        name,
        returnType,
        args,
        inline=False,
        static=False,
        virtual=False,
        const=False,
        bodyInHeader=False,
        templateArgs=None,
        visibility="public",
        body=None,
        breakAfterReturnDecl="\n",
        breakAfterSelf="\n",
        override=False,
        canRunScript=False,
        noDiscard=False,
        delete=False,
    ):
        """
        override indicates whether to flag the method as override
        """
        assert not override or virtual
        assert not (override and static)
        assert not (delete and body)
        self.returnType = returnType
        self.args = args
        self.inline = inline or bodyInHeader
        self.static = static
        self.virtual = virtual
        self.const = const
        self.bodyInHeader = bodyInHeader
        self.templateArgs = templateArgs
        self.body = body
        self.breakAfterReturnDecl = breakAfterReturnDecl
        self.breakAfterSelf = breakAfterSelf
        self.override = override
        self.canRunScript = canRunScript
        self.noDiscard = noDiscard
        self.delete = delete
        ClassItem.__init__(self, name, visibility)

    def getDecorators(self, declaring):
        decorators = []
        if self.noDiscard:
            decorators.append("[[nodiscard]]")
        if self.canRunScript:
            decorators.append("MOZ_CAN_RUN_SCRIPT")
        if self.inline:
            decorators.append("inline")
        if declaring:
            if self.static:
                decorators.append("static")
            if self.virtual and not self.override:
                decorators.append("virtual")
        if decorators:
            return " ".join(decorators) + " "
        return ""

    def getBody(self):
        # Override me or pass a string to constructor
        assert self.body is not None
        return self.body

    def declare(self, cgClass):
        templateClause = (
            "template <%s>\n" % ", ".join(self.templateArgs)
            if self.bodyInHeader and self.templateArgs
            else ""
        )
        args = ", ".join([a.declare() for a in self.args])
        if self.delete:
            body = " = delete;\n"
        elif self.bodyInHeader:
            body = indent(self.getBody())
            body = "\n{\n" + body + "}\n"
        else:
            body = ";\n"

        return fill(
            "${templateClause}${decorators}${returnType}${breakAfterReturnDecl}"
            "${name}(${args})${const}${override}${body}"
            "${breakAfterSelf}",
            templateClause=templateClause,
            decorators=self.getDecorators(True),
            returnType=self.returnType,
            breakAfterReturnDecl=self.breakAfterReturnDecl,
            name=self.name,
            args=args,
            const=" const" if self.const else "",
            override=" override" if self.override else "",
            body=body,
            breakAfterSelf=self.breakAfterSelf,
        )

    def define(self, cgClass):
        if self.delete or self.bodyInHeader:
            return ""

        templateArgs = cgClass.templateArgs
        if templateArgs:
            if cgClass.templateSpecialization:
                templateArgs = templateArgs[len(cgClass.templateSpecialization) :]

        if templateArgs:
            templateClause = "template <%s>\n" % ", ".join(
                [str(a) for a in templateArgs]
            )
        else:
            templateClause = ""

        return fill(
            """
            ${templateClause}${decorators}${returnType}
            ${className}::${name}(${args})${const}
            {
              $*{body}
            }
            """,
            templateClause=templateClause,
            decorators=self.getDecorators(False),
            returnType=self.returnType,
            className=cgClass.getNameString(),
            name=self.name,
            args=", ".join([a.define() for a in self.args]),
            const=" const" if self.const else "",
            body=self.getBody(),
        )


class ClassUsingDeclaration(ClassItem):
    """
    Used for declaring an alias for a type in a CGClass

    name is the name of the alias

    type is the type to declare an alias of

    visibility determines the visibility of the alias (public,
    protected, private), defaults to public.
    """

    def __init__(self, name, type, visibility="public"):
        self.type = type
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        return "using %s = %s;\n\n" % (self.name, self.type)

    def define(self, cgClass):
        return ""


class ClassUsingFromBaseDeclaration(ClassItem):
    """
    Used for importing a name from a base class into a CGClass

    baseClass is the name of the base class to import the name from

    name is the name to import

    visibility determines the visibility of the name (public,
    protected, private), defaults to public.
    """

    def __init__(self, baseClass, name, visibility="public"):
        self.baseClass = baseClass
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        return "using %s::%s;\n\n" % (self.baseClass, self.name)

    def define(self, cgClass):
        return ""


class ClassConstructor(ClassItem):
    """
    Used for adding a constructor to a CGClass.

    args is a list of Argument objects that are the arguments taken by the
    constructor.

    inline should be True if the constructor should be marked inline.

    bodyInHeader should be True if the body should be placed in the class
    declaration in the header.

    default should be True if the definition of the constructor should be
    `= default;`.

    visibility determines the visibility of the constructor (public,
    protected, private), defaults to private.

    explicit should be True if the constructor should be marked explicit.

    baseConstructors is a list of strings containing calls to base constructors,
    defaults to None.

    body contains a string with the code for the constructor, defaults to empty.
    """

    def __init__(
        self,
        args,
        inline=False,
        bodyInHeader=False,
        default=False,
        visibility="private",
        explicit=False,
        constexpr=False,
        baseConstructors=None,
        body="",
    ):
        assert not (inline and constexpr)
        assert not (bodyInHeader and constexpr)
        assert not (default and body)
        self.args = args
        self.inline = inline or bodyInHeader
        self.bodyInHeader = bodyInHeader or constexpr or default
        self.default = default
        self.explicit = explicit
        self.constexpr = constexpr
        self.baseConstructors = baseConstructors or []
        self.body = body
        ClassItem.__init__(self, None, visibility)

    def getDecorators(self, declaring):
        decorators = []
        if declaring:
            if self.explicit:
                decorators.append("explicit")
            if self.inline:
                decorators.append("inline")
            if self.constexpr:
                decorators.append("constexpr")
        if decorators:
            return " ".join(decorators) + " "
        return ""

    def getInitializationList(self, cgClass):
        items = [str(c) for c in self.baseConstructors]
        for m in cgClass.members:
            if not m.static:
                initialize = m.body
                if initialize:
                    items.append(m.name + "(" + initialize + ")")

        if len(items) > 0:
            return "\n  : " + ",\n    ".join(items)
        return ""

    def getBody(self):
        return self.body

    def declare(self, cgClass):
        args = ", ".join([a.declare() for a in self.args])
        if self.bodyInHeader:
            if self.default:
                body = " = default;\n"
            else:
                body = (
                    self.getInitializationList(cgClass)
                    + "\n{\n"
                    + indent(self.getBody())
                    + "}\n"
                )
        else:
            body = ";\n"

        return fill(
            "${decorators}${className}(${args})${body}\n",
            decorators=self.getDecorators(True),
            className=cgClass.getNameString(),
            args=args,
            body=body,
        )

    def define(self, cgClass):
        if self.bodyInHeader:
            return ""

        return fill(
            """
            ${decorators}
            ${className}::${className}(${args})${initializationList}
            {
              $*{body}
            }
            """,
            decorators=self.getDecorators(False),
            className=cgClass.getNameString(),
            args=", ".join([a.define() for a in self.args]),
            initializationList=self.getInitializationList(cgClass),
            body=self.getBody(),
        )


class ClassDestructor(ClassItem):
    """
    Used for adding a destructor to a CGClass.

    inline should be True if the destructor should be marked inline.

    bodyInHeader should be True if the body should be placed in the class
    declaration in the header.

    visibility determines the visibility of the destructor (public,
    protected, private), defaults to private.

    body contains a string with the code for the destructor, defaults to empty.

    virtual determines whether the destructor is virtual, defaults to False.
    """

    def __init__(
        self,
        inline=False,
        bodyInHeader=False,
        visibility="private",
        body="",
        virtual=False,
    ):
        self.inline = inline or bodyInHeader
        self.bodyInHeader = bodyInHeader
        self.body = body
        self.virtual = virtual
        ClassItem.__init__(self, None, visibility)

    def getDecorators(self, declaring):
        decorators = []
        if self.virtual and declaring:
            decorators.append("virtual")
        if self.inline and declaring:
            decorators.append("inline")
        if decorators:
            return " ".join(decorators) + " "
        return ""

    def getBody(self):
        return self.body

    def declare(self, cgClass):
        if self.bodyInHeader:
            body = "\n{\n" + indent(self.getBody()) + "}\n"
        else:
            body = ";\n"

        return fill(
            "${decorators}~${className}()${body}\n",
            decorators=self.getDecorators(True),
            className=cgClass.getNameString(),
            body=body,
        )

    def define(self, cgClass):
        if self.bodyInHeader:
            return ""
        return fill(
            """
            ${decorators}
            ${className}::~${className}()
            {
              $*{body}
            }
            """,
            decorators=self.getDecorators(False),
            className=cgClass.getNameString(),
            body=self.getBody(),
        )


class ClassMember(ClassItem):
    def __init__(
        self,
        name,
        type,
        visibility="private",
        static=False,
        body=None,
        hasIgnoreInitCheckFlag=False,
    ):
        self.type = type
        self.static = static
        self.body = body
        self.hasIgnoreInitCheckFlag = hasIgnoreInitCheckFlag
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        return "%s%s%s %s;\n" % (
            "static " if self.static else "",
            "MOZ_INIT_OUTSIDE_CTOR " if self.hasIgnoreInitCheckFlag else "",
            self.type,
            self.name,
        )

    def define(self, cgClass):
        if not self.static:
            return ""
        if self.body:
            body = " = " + self.body
        else:
            body = ""
        return "%s %s::%s%s;\n" % (self.type, cgClass.getNameString(), self.name, body)


class ClassEnum(ClassItem):
    def __init__(
        self, name, entries, values=None, visibility="public", enumClass=False
    ):
        self.entries = entries
        self.values = values
        self.enumClass = enumClass
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        entries = []
        for i in range(0, len(self.entries)):
            if not self.values or i >= len(self.values):
                entry = "%s" % self.entries[i]
            else:
                entry = "%s = %s" % (self.entries[i], self.values[i])
            entries.append(entry)

        decl = ["enum"]
        self.enumClass and decl.append("class")
        self.name and decl.append(self.name)
        decl = " ".join(decl)

        return "%s\n{\n%s\n};\n" % (decl, indent(",\n".join(entries)))

    def define(self, cgClass):
        # Only goes in the header
        return ""


class ClassUnion(ClassItem):
    def __init__(self, name, entries, visibility="public"):
        self.entries = [entry + ";\n" for entry in entries]
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        return "union %s\n{\n%s\n};\n" % (self.name, indent("".join(self.entries)))

    def define(self, cgClass):
        # Only goes in the header
        return ""


class ClassGroup(ClassItem):
    def __init__(self, items):
        self.items = items
        ClassItem.__init__(self, "", items[0].visibility)

    def declare(self, cgClass):
        assert False

    def define(self, cgClass):
        assert False


class CGClass(CGThing):
    def __init__(
        self,
        name,
        bases=[],
        typeAliases=[],
        members=[],
        constructors=[],
        destructor=None,
        methods=[],
        enums=[],
        unions=[],
        templateArgs=[],
        templateSpecialization=[],
        isStruct=False,
        disallowCopyConstruction=False,
        indent="",
        decorators="",
        extradeclarations="",
        extradefinitions="",
    ):
        CGThing.__init__(self)
        self.name = name
        self.bases = bases
        self.typeAliases = typeAliases
        self.members = members
        self.constructors = constructors
        # We store our single destructor in a list, since all of our
        # code wants lists of members.
        self.destructors = [destructor] if destructor else []
        self.methods = methods
        self.enums = enums
        self.unions = unions
        self.templateArgs = templateArgs
        self.templateSpecialization = templateSpecialization
        self.isStruct = isStruct
        self.disallowCopyConstruction = disallowCopyConstruction
        self.indent = indent
        self.defaultVisibility = "public" if isStruct else "private"
        self.decorators = decorators
        self.extradeclarations = extradeclarations
        self.extradefinitions = extradefinitions

    def getNameString(self):
        className = self.name
        if self.templateSpecialization:
            className += "<%s>" % ", ".join(
                [str(a) for a in self.templateSpecialization]
            )
        return className

    @staticmethod
    def flattenClassItemLists(l):
        for item in l:
            if isinstance(item, ClassGroup):
                for inner in CGClass.flattenClassItemLists(item.items):
                    yield inner
            else:
                yield item

    def declare(self):
        result = ""
        if self.templateArgs:
            templateArgs = [a.declare() for a in self.templateArgs]
            templateArgs = templateArgs[len(self.templateSpecialization) :]
            result += "template <%s>\n" % ",".join([str(a) for a in templateArgs])

        type = "struct" if self.isStruct else "class"

        if self.templateSpecialization:
            specialization = "<%s>" % ", ".join(
                [str(a) for a in self.templateSpecialization]
            )
        else:
            specialization = ""

        myself = "%s %s%s" % (type, self.name, specialization)
        if self.decorators != "":
            myself += " " + self.decorators
        result += myself

        if self.bases:
            inherit = " : "
            result += inherit
            # Grab our first base
            baseItems = [CGGeneric(b.declare(self)) for b in self.bases]
            bases = baseItems[:1]
            # Indent the rest
            bases.extend(
                CGIndenter(b, len(myself) + len(inherit)) for b in baseItems[1:]
            )
            result += ",\n".join(b.define() for b in bases)

        result += "\n{\n"

        result += self.extradeclarations

        def declareMembers(cgClass, memberList, defaultVisibility):
            members = {"private": [], "protected": [], "public": []}

            for member in memberList:
                members[member.visibility].append(member)

            if defaultVisibility == "public":
                order = ["public", "protected", "private"]
            else:
                order = ["private", "protected", "public"]

            result = ""

            lastVisibility = defaultVisibility
            for visibility in order:
                list = members[visibility]
                if list:
                    for member in self.flattenClassItemLists(list):
                        if member.visibility != lastVisibility:
                            result += member.visibility + ":\n"
                        result += indent(member.declare(cgClass))
                        lastVisibility = member.visibility
            return (result, lastVisibility)

        if self.disallowCopyConstruction:

            class DisallowedCopyConstructor(object):
                def __init__(self):
                    self.visibility = "private"

                def declare(self, cgClass):
                    name = cgClass.getNameString()
                    return (
                        "%s(const %s&) = delete;\n"
                        "%s& operator=(const %s&) = delete;\n"
                        % (name, name, name, name)
                    )

            disallowedCopyConstructors = [DisallowedCopyConstructor()]
        else:
            disallowedCopyConstructors = []

        order = [
            self.typeAliases,
            self.enums,
            self.unions,
            self.members,
            self.constructors + disallowedCopyConstructors,
            self.destructors,
            self.methods,
        ]

        lastVisibility = self.defaultVisibility
        pieces = []
        for memberList in order:
            code, lastVisibility = declareMembers(self, memberList, lastVisibility)

            if code:
                code = code.rstrip() + "\n"  # remove extra blank lines at the end
                pieces.append(code)

        result += "\n".join(pieces)
        result += "};\n"
        result = indent(result, len(self.indent))
        return result

    def define(self):
        def defineMembers(cgClass, memberList, itemCount, separator=""):
            result = ""
            for member in self.flattenClassItemLists(memberList):
                if itemCount != 0:
                    result = result + separator
                definition = member.define(cgClass)
                if definition:
                    # Member variables would only produce empty lines here.
                    result += definition
                    itemCount += 1
            return (result, itemCount)

        order = [
            (self.members, ""),
            (self.constructors, "\n"),
            (self.destructors, "\n"),
            (self.methods, "\n"),
        ]

        result = self.extradefinitions
        itemCount = 0
        for memberList, separator in order:
            memberString, itemCount = defineMembers(
                self, memberList, itemCount, separator
            )
            result = result + memberString
        return result


class CGResolveOwnPropertyViaResolve(CGAbstractBindingMethod):
    """
    An implementation of Xray ResolveOwnProperty stuff for things that have a
    resolve hook.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "wrapper"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::MutableHandle<Maybe<JS::PropertyDescriptor>>", "desc"),
        ]
        CGAbstractBindingMethod.__init__(
            self,
            descriptor,
            "ResolveOwnPropertyViaResolve",
            args,
            getThisObj="",
            callArgs="",
        )

    def generate_code(self):
        return CGGeneric(
            dedent(
                """
            {
              // Since we're dealing with an Xray, do the resolve on the
              // underlying object first.  That gives it a chance to
              // define properties on the actual object as needed, and
              // then use the fact that it created the objects as a flag
              // to avoid re-resolving the properties if someone deletes
              // them.
              JSAutoRealm ar(cx, obj);
              JS_MarkCrossZoneId(cx, id);
              JS::Rooted<mozilla::Maybe<JS::PropertyDescriptor>> objDesc(cx);
              if (!self->DoResolve(cx, obj, id, &objDesc)) {
                return false;
              }
              // If desc->value() is undefined, then the DoResolve call
              // has already defined the property on the object.  Don't
              // try to also define it.
              if (objDesc.isSome() &&
                  !objDesc->value().isUndefined()) {
                JS::Rooted<JS::PropertyDescriptor> defineDesc(cx, *objDesc);
                if (!JS_DefinePropertyById(cx, obj, id, defineDesc)) {
                  return false;
                }
              }
            }
            return self->DoResolve(cx, wrapper, id, desc);
            """
            )
        )


class CGEnumerateOwnPropertiesViaGetOwnPropertyNames(CGAbstractBindingMethod):
    """
    An implementation of Xray EnumerateOwnProperties stuff for things
    that have a resolve hook.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "wrapper"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("JS::MutableHandleVector<jsid>", "props"),
        ]
        CGAbstractBindingMethod.__init__(
            self,
            descriptor,
            "EnumerateOwnPropertiesViaGetOwnPropertyNames",
            args,
            getThisObj="",
            callArgs="",
        )

    def generate_code(self):
        return CGGeneric(
            dedent(
                """
            FastErrorResult rv;
            // This wants all own props, not just enumerable ones.
            self->GetOwnPropertyNames(cx, props, false, rv);
            if (rv.MaybeSetPendingException(cx)) {
              return false;
            }
            return true;
            """
            )
        )


class CGPrototypeTraitsClass(CGClass):
    def __init__(self, descriptor, indent=""):
        templateArgs = [Argument("prototypes::ID", "PrototypeID")]
        templateSpecialization = ["prototypes::id::" + descriptor.name]
        enums = [ClassEnum("", ["Depth"], [descriptor.interface.inheritanceDepth()])]
        CGClass.__init__(
            self,
            "PrototypeTraits",
            indent=indent,
            templateArgs=templateArgs,
            templateSpecialization=templateSpecialization,
            enums=enums,
            isStruct=True,
        )

    def deps(self):
        return set()


class CGClassForwardDeclare(CGThing):
    def __init__(self, name, isStruct=False):
        CGThing.__init__(self)
        self.name = name
        self.isStruct = isStruct

    def declare(self):
        type = "struct" if self.isStruct else "class"
        return "%s %s;\n" % (type, self.name)

    def define(self):
        # Header only
        return ""

    def deps(self):
        return set()


class CGProxySpecialOperation(CGPerSignatureCall):
    """
    Base class for classes for calling an indexed or named special operation
    (don't use this directly, use the derived classes below).

    If checkFound is False, will just assert that the prop is found instead of
    checking that it is before wrapping the value.

    resultVar: See the docstring for CGCallGenerator.

    foundVar: For getters and deleters, the generated code can also set a bool
    variable, declared by the caller, if the given indexed or named property
    already existed. If the caller wants this, it should pass the name of the
    bool variable as the foundVar keyword argument to the constructor. The
    caller is responsible for declaring the variable and initializing it to
    false.
    """

    def __init__(
        self,
        descriptor,
        operation,
        checkFound=True,
        argumentHandleValue=None,
        resultVar=None,
        foundVar=None,
    ):
        self.checkFound = checkFound
        self.foundVar = foundVar or "found"

        nativeName = MakeNativeName(descriptor.binaryNameFor(operation, False))
        operation = descriptor.operations[operation]
        assert len(operation.signatures()) == 1
        signature = operation.signatures()[0]

        returnType, arguments = signature

        # We pass len(arguments) as the final argument so that the
        # CGPerSignatureCall won't do any argument conversion of its own.
        CGPerSignatureCall.__init__(
            self,
            returnType,
            arguments,
            nativeName,
            False,
            descriptor,
            operation,
            len(arguments),
            resultVar=resultVar,
            objectName="proxy",
        )

        if operation.isSetter():
            # arguments[0] is the index or name of the item that we're setting.
            argument = arguments[1]
            info = getJSToNativeConversionInfo(
                argument.type,
                descriptor,
                sourceDescription=(
                    "value being assigned to %s setter"
                    % descriptor.interface.identifier.name
                ),
            )
            if argumentHandleValue is None:
                argumentHandleValue = "desc.value()"
            rootedValue = fill(
                """
                JS::Rooted<JS::Value> rootedValue(cx, ${argumentHandleValue});
                """,
                argumentHandleValue=argumentHandleValue,
            )
            templateValues = {
                "declName": argument.identifier.name,
                "holderName": argument.identifier.name + "_holder",
                "val": argumentHandleValue,
                "maybeMutableVal": "&rootedValue",
                "obj": "obj",
                "passedToJSImpl": "false",
            }
            self.cgRoot.prepend(instantiateJSToNativeConversion(info, templateValues))
            # rootedValue needs to come before the conversion, so we
            # need to prepend it last.
            self.cgRoot.prepend(CGGeneric(rootedValue))
        elif operation.isGetter() or operation.isDeleter():
            if foundVar is None:
                self.cgRoot.prepend(CGGeneric("bool found = false;\n"))

    def getArguments(self):
        args = [(a, a.identifier.name) for a in self.arguments]
        if self.idlNode.isGetter() or self.idlNode.isDeleter():
            args.append(
                (
                    FakeArgument(BuiltinTypes[IDLBuiltinType.Types.boolean]),
                    self.foundVar,
                )
            )
        return args

    def wrap_return_value(self):
        if not self.idlNode.isGetter() or self.templateValues is None:
            return ""

        wrap = CGGeneric(
            wrapForType(self.returnType, self.descriptor, self.templateValues)
        )
        if self.checkFound:
            wrap = CGIfWrapper(wrap, self.foundVar)
        else:
            wrap = CGList([CGGeneric("MOZ_ASSERT(" + self.foundVar + ");\n"), wrap])
        return "\n" + wrap.define()


class CGProxyIndexedOperation(CGProxySpecialOperation):
    """
    Class to generate a call to an indexed operation.

    If doUnwrap is False, the caller is responsible for making sure a variable
    named 'self' holds the C++ object somewhere where the code we generate
    will see it.

    If checkFound is False, will just assert that the prop is found instead of
    checking that it is before wrapping the value.

    resultVar: See the docstring for CGCallGenerator.

    foundVar: See the docstring for CGProxySpecialOperation.
    """

    def __init__(
        self,
        descriptor,
        name,
        doUnwrap=True,
        checkFound=True,
        argumentHandleValue=None,
        resultVar=None,
        foundVar=None,
    ):
        self.doUnwrap = doUnwrap
        CGProxySpecialOperation.__init__(
            self,
            descriptor,
            name,
            checkFound,
            argumentHandleValue=argumentHandleValue,
            resultVar=resultVar,
            foundVar=foundVar,
        )

    def define(self):
        # Our first argument is the id we're getting.
        argName = self.arguments[0].identifier.name
        if argName == "index":
            # We already have our index in a variable with that name
            setIndex = ""
        else:
            setIndex = "uint32_t %s = index;\n" % argName
        if self.doUnwrap:
            unwrap = "%s* self = UnwrapProxy(proxy);\n" % self.descriptor.nativeType
        else:
            unwrap = ""
        return setIndex + unwrap + CGProxySpecialOperation.define(self)


class CGProxyIndexedGetter(CGProxyIndexedOperation):
    """
    Class to generate a call to an indexed getter. If templateValues is not None
    the returned value will be wrapped with wrapForType using templateValues.

    If doUnwrap is False, the caller is responsible for making sure a variable
    named 'self' holds the C++ object somewhere where the code we generate
    will see it.

    If checkFound is False, will just assert that the prop is found instead of
    checking that it is before wrapping the value.

    foundVar: See the docstring for CGProxySpecialOperation.
    """

    def __init__(
        self,
        descriptor,
        templateValues=None,
        doUnwrap=True,
        checkFound=True,
        foundVar=None,
    ):
        self.templateValues = templateValues
        CGProxyIndexedOperation.__init__(
            self, descriptor, "IndexedGetter", doUnwrap, checkFound, foundVar=foundVar
        )


class CGProxyIndexedPresenceChecker(CGProxyIndexedGetter):
    """
    Class to generate a call that checks whether an indexed property exists.

    For now, we just delegate to CGProxyIndexedGetter

    foundVar: See the docstring for CGProxySpecialOperation.
    """

    def __init__(self, descriptor, foundVar):
        CGProxyIndexedGetter.__init__(self, descriptor, foundVar=foundVar)
        self.cgRoot.append(CGGeneric("(void)result;\n"))


class CGProxyIndexedSetter(CGProxyIndexedOperation):
    """
    Class to generate a call to an indexed setter.
    """

    def __init__(self, descriptor, argumentHandleValue=None):
        CGProxyIndexedOperation.__init__(
            self, descriptor, "IndexedSetter", argumentHandleValue=argumentHandleValue
        )


class CGProxyNamedOperation(CGProxySpecialOperation):
    """
    Class to generate a call to a named operation.

    'value' is the jsval to use for the name; None indicates that it should be
    gotten from the property id.

    resultVar: See the docstring for CGCallGenerator.

    foundVar: See the docstring for CGProxySpecialOperation.

    tailCode: if we end up with a non-symbol string id, run this code after
              we do all our other work.
    """

    def __init__(
        self,
        descriptor,
        name,
        value=None,
        argumentHandleValue=None,
        resultVar=None,
        foundVar=None,
        tailCode="",
    ):
        CGProxySpecialOperation.__init__(
            self,
            descriptor,
            name,
            argumentHandleValue=argumentHandleValue,
            resultVar=resultVar,
            foundVar=foundVar,
        )
        self.value = value
        self.tailCode = tailCode

    def define(self):
        # Our first argument is the id we're getting.
        argName = self.arguments[0].identifier.name
        if argName == "id":
            # deal with the name collision
            decls = "JS::Rooted<jsid> id_(cx, id);\n"
            idName = "id_"
        else:
            decls = ""
            idName = "id"

        decls += "FakeString<char16_t> %s;\n" % argName

        main = fill(
            """
            ${nativeType}* self = UnwrapProxy(proxy);
            $*{op}
            $*{tailCode}
            """,
            nativeType=self.descriptor.nativeType,
            op=CGProxySpecialOperation.define(self),
            tailCode=self.tailCode,
        )

        if self.value is None:
            return fill(
                """
                $*{decls}
                bool isSymbol;
                if (!ConvertIdToString(cx, ${idName}, ${argName}, isSymbol)) {
                  return false;
                }
                if (!isSymbol) {
                  $*{main}
                }
                """,
                decls=decls,
                idName=idName,
                argName=argName,
                main=main,
            )

        # Sadly, we have to set up nameVal even if we have an atom id,
        # because we don't know for sure, and we can end up needing it
        # so it needs to be higher up the stack.  Using a Maybe here
        # seems like probable overkill.
        return fill(
            """
            $*{decls}
            JS::Rooted<JS::Value> nameVal(cx, ${value});
            if (!nameVal.isSymbol()) {
              if (!ConvertJSValueToString(cx, nameVal, eStringify, eStringify,
                                          ${argName})) {
                return false;
              }
              $*{main}
            }
            """,
            decls=decls,
            value=self.value,
            argName=argName,
            main=main,
        )


class CGProxyNamedGetter(CGProxyNamedOperation):
    """
    Class to generate a call to an named getter. If templateValues is not None
    the returned value will be wrapped with wrapForType using templateValues.
    'value' is the jsval to use for the name; None indicates that it should be
    gotten from the property id.

    foundVar: See the docstring for CGProxySpecialOperation.
    """

    def __init__(self, descriptor, templateValues=None, value=None, foundVar=None):
        self.templateValues = templateValues
        CGProxyNamedOperation.__init__(
            self, descriptor, "NamedGetter", value, foundVar=foundVar
        )


class CGProxyNamedPresenceChecker(CGProxyNamedGetter):
    """
    Class to generate a call that checks whether a named property exists.

    For now, we just delegate to CGProxyNamedGetter

    foundVar: See the docstring for CGProxySpecialOperation.
    """

    def __init__(self, descriptor, foundVar=None):
        CGProxyNamedGetter.__init__(self, descriptor, foundVar=foundVar)
        self.cgRoot.append(CGGeneric("(void)result;\n"))


class CGProxyNamedSetter(CGProxyNamedOperation):
    """
    Class to generate a call to a named setter.
    """

    def __init__(self, descriptor, tailCode, argumentHandleValue=None):
        CGProxyNamedOperation.__init__(
            self,
            descriptor,
            "NamedSetter",
            argumentHandleValue=argumentHandleValue,
            tailCode=tailCode,
        )


class CGProxyNamedDeleter(CGProxyNamedOperation):
    """
    Class to generate a call to a named deleter.

    resultVar: See the docstring for CGCallGenerator.

    foundVar: See the docstring for CGProxySpecialOperation.
    """

    def __init__(self, descriptor, resultVar=None, foundVar=None):
        CGProxyNamedOperation.__init__(
            self, descriptor, "NamedDeleter", resultVar=resultVar, foundVar=foundVar
        )


class CGProxyIsProxy(CGAbstractMethod):
    def __init__(self, descriptor):
        args = [Argument("JSObject*", "obj")]
        CGAbstractMethod.__init__(
            self, descriptor, "IsProxy", "bool", args, alwaysInline=True
        )

    def declare(self):
        return ""

    def definition_body(self):
        return "return js::IsProxy(obj) && js::GetProxyHandler(obj) == DOMProxyHandler::getInstance();\n"


class CGProxyUnwrap(CGAbstractMethod):
    def __init__(self, descriptor):
        args = [Argument("JSObject*", "obj")]
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "UnwrapProxy",
            descriptor.nativeType + "*",
            args,
            alwaysInline=True,
        )

    def declare(self):
        return ""

    def definition_body(self):
        return fill(
            """
            MOZ_ASSERT(js::IsProxy(obj));
            if (js::GetProxyHandler(obj) != DOMProxyHandler::getInstance()) {
              MOZ_ASSERT(xpc::WrapperFactory::IsXrayWrapper(obj));
              obj = js::UncheckedUnwrap(obj);
            }
            MOZ_ASSERT(IsProxy(obj));
            return static_cast<${type}*>(js::GetProxyReservedSlot(obj, DOM_OBJECT_SLOT).toPrivate());
            """,
            type=self.descriptor.nativeType,
        )


MISSING_PROP_PREF = "dom.missing_prop_counters.enabled"


def missingPropUseCountersForDescriptor(desc):
    if not desc.needsMissingPropUseCounters:
        return ""

    return fill(
        """
        if (StaticPrefs::${pref}() && id.isAtom()) {
          CountMaybeMissingProperty(proxy, id);
        }

        """,
        pref=prefIdentifier(MISSING_PROP_PREF),
    )


def findAncestorWithInstrumentedProps(desc):
    """
    Find an ancestor of desc.interface (not including desc.interface
    itself) that has instrumented properties on it.  May return None
    if there is no such ancestor.
    """
    ancestor = desc.interface.parent
    while ancestor:
        if ancestor.getExtendedAttribute("InstrumentedProps"):
            return ancestor
        ancestor = ancestor.parent
    return None


class CGCountMaybeMissingProperty(CGAbstractMethod):
    def __init__(self, descriptor):
        """
        Returns whether we counted the property involved.
        """
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "CountMaybeMissingProperty",
            "bool",
            [
                Argument("JS::Handle<JSObject*>", "proxy"),
                Argument("JS::Handle<jsid>", "id"),
            ],
        )

    def gen_switch(self, switchDecriptor):
        """
        Generate a switch from the switch descriptor.  The descriptor
        dictionary must have the following properties:

        1) A "precondition" property that contains code to run before the
           switch statement.  Its value ie a string.
        2) A "condition" property for the condition.  Its value is a string.
        3) A "cases" property.  Its value is an object that has property names
           corresponding to the case labels.  The values of those properties
           are either new switch descriptor dictionaries (which will then
           generate nested switches) or strings to use for case bodies.
        """
        cases = []
        for label, body in sorted(switchDecriptor["cases"].items()):
            if isinstance(body, dict):
                body = self.gen_switch(body)
            cases.append(
                fill(
                    """
                case ${label}: {
                  $*{body}
                  break;
                }
                """,
                    label=label,
                    body=body,
                )
            )
        return fill(
            """
            $*{precondition}
            switch (${condition}) {
              $*{cases}
            }
            """,
            precondition=switchDecriptor["precondition"],
            condition=switchDecriptor["condition"],
            cases="".join(cases),
        )

    def charSwitch(self, props, charIndex):
        """
        Create a switch for the given props, based on the first char where
        they start to differ at index charIndex or more.  Each prop is a tuple
        containing interface name and prop name.

        Incoming props should be a sorted list.
        """
        if len(props) == 1:
            # We're down to one string: just check whether we match it.
            return fill(
                """
                if (JS_LinearStringEqualsLiteral(str, "${name}")) {
                  counter.emplace(eUseCounter_${iface}_${name});
                }
                """,
                iface=self.descriptor.name,
                name=props[0],
            )

        switch = dict()
        if charIndex == 0:
            switch["precondition"] = "StringIdChars chars(nogc, str);\n"
        else:
            switch["precondition"] = ""

        # Find the first place where we might actually have a difference.
        while all(prop[charIndex] == props[0][charIndex] for prop in props):
            charIndex += 1

        switch["condition"] = "chars[%d]" % charIndex
        switch["cases"] = dict()
        current_props = None
        curChar = None
        idx = 0
        while idx < len(props):
            nextChar = "'%s'" % props[idx][charIndex]
            if nextChar != curChar:
                if curChar:
                    switch["cases"][curChar] = self.charSwitch(
                        current_props, charIndex + 1
                    )
                current_props = []
                curChar = nextChar
            current_props.append(props[idx])
            idx += 1
        switch["cases"][curChar] = self.charSwitch(current_props, charIndex + 1)
        return switch

    def definition_body(self):
        ancestor = findAncestorWithInstrumentedProps(self.descriptor)

        if ancestor:
            body = fill(
                """
                if (${ancestor}_Binding::CountMaybeMissingProperty(proxy, id)) {
                  return true;
                }

                """,
                ancestor=ancestor.identifier.name,
            )
        else:
            body = ""

        instrumentedProps = self.descriptor.instrumentedProps
        if not instrumentedProps:
            return body + dedent(
                """
                return false;
                """
            )

        lengths = set(len(prop) for prop in instrumentedProps)
        switchDesc = {"condition": "JS::GetLinearStringLength(str)", "precondition": ""}
        switchDesc["cases"] = dict()
        for length in sorted(lengths):
            switchDesc["cases"][str(length)] = self.charSwitch(
                list(sorted(prop for prop in instrumentedProps if len(prop) == length)),
                0,
            )

        return body + fill(
            """
            MOZ_ASSERT(StaticPrefs::${pref}() && id.isAtom());
            Maybe<UseCounter> counter;
            {
              // Scope for our no-GC section, so we don't need to rely on SetUseCounter not GCing.
              JS::AutoCheckCannotGC nogc;
              JSLinearString* str = JS::AtomToLinearString(id.toAtom());
              // Don't waste time fetching the chars until we've done the length switch.
              $*{switch}
            }
            if (counter) {
              SetUseCounter(proxy, *counter);
              return true;
            }

            return false;
            """,
            pref=prefIdentifier(MISSING_PROP_PREF),
            switch=self.gen_switch(switchDesc),
        )


class CGDOMJSProxyHandler_getOwnPropDescriptor(ClassMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("bool", "ignoreNamedProps"),
            Argument("JS::MutableHandle<Maybe<JS::PropertyDescriptor>>", "desc"),
        ]
        ClassMethod.__init__(
            self,
            "getOwnPropDescriptor",
            "bool",
            args,
            virtual=True,
            override=True,
            const=True,
        )
        self.descriptor = descriptor

    def getBody(self):
        indexedSetter = self.descriptor.operations["IndexedSetter"]

        if self.descriptor.isMaybeCrossOriginObject():
            xrayDecl = dedent(
                """
                MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy));
                MOZ_ASSERT(IsPlatformObjectSameOrigin(cx, proxy),
                           "getOwnPropertyDescriptor() and set() should have dealt");
                MOZ_ASSERT(js::IsObjectInContextCompartment(proxy, cx),
                           "getOwnPropertyDescriptor() and set() should have dealt");

                """
            )
            xrayCheck = ""
        else:
            xrayDecl = "bool isXray = xpc::WrapperFactory::IsXrayWrapper(proxy);\n"
            xrayCheck = "!isXray &&"

        if self.descriptor.supportsIndexedProperties():
            attributes = [
                "JS::PropertyAttribute::Configurable",
                "JS::PropertyAttribute::Enumerable",
            ]
            if indexedSetter is not None:
                attributes.append("JS::PropertyAttribute::Writable")
            setDescriptor = (
                "desc.set(mozilla::Some(JS::PropertyDescriptor::Data(value, { %s })));\nreturn true;\n"
                % ", ".join(attributes)
            )
            templateValues = {
                "jsvalRef": "value",
                "jsvalHandle": "&value",
                "obj": "proxy",
                "successCode": setDescriptor,
            }
            getIndexed = fill(
                """
                uint32_t index = GetArrayIndexFromId(id);
                if (IsArrayIndex(index)) {
                  JS::Rooted<JS::Value> value(cx);
                  $*{callGetter}
                }

                """,
                callGetter=CGProxyIndexedGetter(
                    self.descriptor, templateValues
                ).define(),
            )
        else:
            getIndexed = ""

        missingPropUseCounters = missingPropUseCountersForDescriptor(self.descriptor)

        if self.descriptor.supportsNamedProperties():
            operations = self.descriptor.operations
            attributes = ["JS::PropertyAttribute::Configurable"]
            if self.descriptor.namedPropertiesEnumerable:
                attributes.append("JS::PropertyAttribute::Enumerable")
            if operations["NamedSetter"] is not None:
                attributes.append("JS::PropertyAttribute::Writable")
            setDescriptor = (
                "desc.set(mozilla::Some(JS::PropertyDescriptor::Data(value, { %s })));\nreturn true;\n"
                % ", ".join(attributes)
            )
            templateValues = {
                "jsvalRef": "value",
                "jsvalHandle": "&value",
                "obj": "proxy",
                "successCode": setDescriptor,
            }

            computeCondition = dedent(
                """
                bool hasOnProto;
                if (!HasPropertyOnPrototype(cx, proxy, id, &hasOnProto)) {
                  return false;
                }
                callNamedGetter = !hasOnProto;
                """
            )
            if self.descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns"):
                computeCondition = fill(
                    """
                    if (!isXray) {
                      callNamedGetter = true;
                    } else {
                      $*{hasOnProto}
                    }
                    """,
                    hasOnProto=computeCondition,
                )

            outerCondition = "!ignoreNamedProps"
            if self.descriptor.supportsIndexedProperties():
                outerCondition = "!IsArrayIndex(index) && " + outerCondition

            namedGetCode = CGProxyNamedGetter(self.descriptor, templateValues).define()
            namedGet = fill(
                """
                bool callNamedGetter = false;
                if (${outerCondition}) {
                  $*{computeCondition}
                }
                if (callNamedGetter) {
                  JS::Rooted<JS::Value> value(cx);
                  $*{namedGetCode}
                }
                """,
                outerCondition=outerCondition,
                computeCondition=computeCondition,
                namedGetCode=namedGetCode,
            )
            namedGet += "\n"
        else:
            namedGet = ""

        return fill(
            """
            $*{xrayDecl}
            $*{getIndexed}
            $*{missingPropUseCounters}
            JS::Rooted<JSObject*> expando(cx);
            if (${xrayCheck}(expando = GetExpandoObject(proxy))) {
              if (!JS_GetOwnPropertyDescriptorById(cx, expando, id, desc)) {
                return false;
              }
              if (desc.isSome()) {
                return true;
              }
            }

            $*{namedGet}
            desc.reset();
            return true;
            """,
            xrayDecl=xrayDecl,
            xrayCheck=xrayCheck,
            getIndexed=getIndexed,
            missingPropUseCounters=missingPropUseCounters,
            namedGet=namedGet,
        )


class CGDOMJSProxyHandler_defineProperty(ClassMethod):
    def __init__(self, descriptor):
        # The usual convention is to name the ObjectOpResult out-parameter
        # `result`, but that name is a bit overloaded around here.
        args = [
            Argument("JSContext*", "cx_"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::Handle<JS::PropertyDescriptor>", "desc"),
            Argument("JS::ObjectOpResult&", "opresult"),
            Argument("bool*", "done"),
        ]
        ClassMethod.__init__(
            self,
            "defineProperty",
            "bool",
            args,
            virtual=True,
            override=True,
            const=True,
        )
        self.descriptor = descriptor

    def getBody(self):
        set = ""

        indexedSetter = self.descriptor.operations["IndexedSetter"]
        if indexedSetter:
            error_label = CGSpecializedMethod.error_reporting_label_helper(
                self.descriptor, indexedSetter, isConstructor=False
            )
            if error_label:
                cxDecl = fill(
                    """
                    BindingCallContext cx(cx_, ${error_label});
                    """,
                    error_label=error_label,
                )
            else:
                cxDecl = dedent(
                    """
                    JSContext* cx = cx_;
                    """
                )
            set += fill(
                """
                uint32_t index = GetArrayIndexFromId(id);
                if (IsArrayIndex(index)) {
                  $*{cxDecl}
                  *done = true;
                  // https://webidl.spec.whatwg.org/#legacy-platform-object-defineownproperty
                  // Step 1.1.  The no-indexed-setter case is handled by step 1.2.
                  if (!desc.isDataDescriptor()) {
                    return opresult.failNotDataDescriptor();
                  }

                  $*{callSetter}
                  return opresult.succeed();
                }
                """,
                cxDecl=cxDecl,
                callSetter=CGProxyIndexedSetter(self.descriptor).define(),
            )
        elif self.descriptor.supportsIndexedProperties():
            # We allow untrusted content to prevent Xrays from setting a
            # property if that property is an indexed property and we have no
            # indexed setter.  That's how the object would normally behave if
            # you tried to set the property on it.  That means we don't need to
            # do anything special for Xrays here.
            set += dedent(
                """
                if (IsArrayIndex(GetArrayIndexFromId(id))) {
                  *done = true;
                  return opresult.failNoIndexedSetter();
                }
                """
            )

        namedSetter = self.descriptor.operations["NamedSetter"]
        if namedSetter:
            error_label = CGSpecializedMethod.error_reporting_label_helper(
                self.descriptor, namedSetter, isConstructor=False
            )
            if error_label:
                set += fill(
                    """
                    BindingCallContext cx(cx_, ${error_label});
                    """,
                    error_label=error_label,
                )
            else:
                set += dedent(
                    """
                    JSContext* cx = cx_;
                    """
                )
            if self.descriptor.hasLegacyUnforgeableMembers:
                raise TypeError(
                    "Can't handle a named setter on an interface "
                    "that has unforgeables.  Figure out how that "
                    "should work!"
                )
            set += dedent(
                """
                // https://webidl.spec.whatwg.org/#legacy-platform-object-defineownproperty
                // Step 2.2.2.1.
                if (!desc.isDataDescriptor()) {
                  *done = true;
                  return opresult.failNotDataDescriptor();
                }
                """
            )
            tailCode = dedent(
                """
                *done = true;
                return opresult.succeed();
                """
            )
            set += CGProxyNamedSetter(self.descriptor, tailCode).define()
        else:
            # We allow untrusted content to prevent Xrays from setting a
            # property if that property is already a named property on the
            # object and we have no named setter.  That's how the object would
            # normally behave if you tried to set the property on it.  That
            # means we don't need to do anything special for Xrays here.
            if self.descriptor.supportsNamedProperties():
                set += fill(
                    """
                    JSContext* cx = cx_;
                    bool found = false;
                    $*{presenceChecker}

                    if (found) {
                      *done = true;
                      return opresult.failNoNamedSetter();
                    }
                    """,
                    presenceChecker=CGProxyNamedPresenceChecker(
                        self.descriptor, foundVar="found"
                    ).define(),
                )
            if self.descriptor.isMaybeCrossOriginObject():
                set += dedent(
                    """
                    MOZ_ASSERT(IsPlatformObjectSameOrigin(cx_, proxy),
                               "Why did the MaybeCrossOriginObject defineProperty override fail?");
                    MOZ_ASSERT(js::IsObjectInContextCompartment(proxy, cx_),
                               "Why did the MaybeCrossOriginObject defineProperty override fail?");
                    """
                )

        # In all cases we want to tail-call to our base class; we can
        # always land here for symbols.
        set += (
            "return mozilla::dom::DOMProxyHandler::defineProperty(%s);\n"
            % ", ".join(a.name for a in self.args)
        )
        return set


def getDeleterBody(descriptor, type, foundVar=None):
    """
    type should be "Named" or "Indexed"

    The possible outcomes:
    - an error happened                       (the emitted code returns false)
    - own property not found                  (foundVar=false, deleteSucceeded=true)
    - own property found and deleted          (foundVar=true,  deleteSucceeded=true)
    - own property found but can't be deleted (foundVar=true,  deleteSucceeded=false)
    """
    assert type in ("Named", "Indexed")
    deleter = descriptor.operations[type + "Deleter"]
    if deleter:
        assert type == "Named"
        assert foundVar is not None
        if descriptor.hasLegacyUnforgeableMembers:
            raise TypeError(
                "Can't handle a deleter on an interface "
                "that has unforgeables.  Figure out how "
                "that should work!"
            )
        # See if the deleter method is fallible.
        t = deleter.signatures()[0][0]
        if t.isPrimitive() and not t.nullable() and t.tag() == IDLType.Tags.bool:
            # The deleter method has a boolean return value. When a
            # property is found, the return value indicates whether it
            # was successfully deleted.
            setDS = fill(
                """
                if (!${foundVar}) {
                  deleteSucceeded = true;
                }
                """,
                foundVar=foundVar,
            )
        else:
            # No boolean return value: if a property is found,
            # deleting it always succeeds.
            setDS = "deleteSucceeded = true;\n"

        body = (
            CGProxyNamedDeleter(
                descriptor, resultVar="deleteSucceeded", foundVar=foundVar
            ).define()
            + setDS
        )
    elif getattr(descriptor, "supports%sProperties" % type)():
        presenceCheckerClass = globals()["CGProxy%sPresenceChecker" % type]
        foundDecl = ""
        if foundVar is None:
            foundVar = "found"
            foundDecl = "bool found = false;\n"
        body = fill(
            """
            $*{foundDecl}
            $*{presenceChecker}
            deleteSucceeded = !${foundVar};
            """,
            foundDecl=foundDecl,
            presenceChecker=presenceCheckerClass(
                descriptor, foundVar=foundVar
            ).define(),
            foundVar=foundVar,
        )
    else:
        body = None
    return body


class CGDeleteNamedProperty(CGAbstractStaticMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "xray"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::ObjectOpResult&", "opresult"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, "DeleteNamedProperty", "bool", args
        )

    def definition_body(self):
        return fill(
            """
            MOZ_ASSERT(xpc::WrapperFactory::IsXrayWrapper(xray));
            MOZ_ASSERT(js::IsProxy(proxy));
            MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy));
            JSAutoRealm ar(cx, proxy);
            bool deleteSucceeded = false;
            bool found = false;
            $*{namedBody}
            if (!found || deleteSucceeded) {
              return opresult.succeed();
            }
            return opresult.failCantDelete();
            """,
            namedBody=getDeleterBody(self.descriptor, "Named", foundVar="found"),
        )


class CGDOMJSProxyHandler_delete(ClassMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::ObjectOpResult&", "opresult"),
        ]
        ClassMethod.__init__(
            self, "delete_", "bool", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        delete = dedent(
            """
            MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy),
                      "Should not have a XrayWrapper here");

            """
        )

        if self.descriptor.isMaybeCrossOriginObject():
            delete += dedent(
                """
                if (!IsPlatformObjectSameOrigin(cx, proxy)) {
                  return ReportCrossOriginDenial(cx, id, "delete"_ns);
                }

                // Safe to enter the Realm of proxy now.
                JSAutoRealm ar(cx, proxy);
                JS_MarkCrossZoneId(cx, id);
                """
            )

        indexedBody = getDeleterBody(self.descriptor, "Indexed")
        if indexedBody is not None:
            # Can't handle cross-origin objects here.
            assert not self.descriptor.isMaybeCrossOriginObject()
            delete += fill(
                """
                uint32_t index = GetArrayIndexFromId(id);
                if (IsArrayIndex(index)) {
                  bool deleteSucceeded;
                  $*{indexedBody}
                  return deleteSucceeded ? opresult.succeed() : opresult.failCantDelete();
                }
                """,
                indexedBody=indexedBody,
            )

        namedBody = getDeleterBody(self.descriptor, "Named", foundVar="found")
        if namedBody is not None:
            delete += dedent(
                """
                // Try named delete only if the named property visibility
                // algorithm says the property is visible.
                bool tryNamedDelete = true;
                { // Scope for expando
                  JS::Rooted<JSObject*> expando(cx, DOMProxyHandler::GetExpandoObject(proxy));
                  if (expando) {
                    bool hasProp;
                    if (!JS_HasPropertyById(cx, expando, id, &hasProp)) {
                      return false;
                    }
                    tryNamedDelete = !hasProp;
                  }
                }
                """
            )

            if not self.descriptor.interface.getExtendedAttribute(
                "LegacyOverrideBuiltIns"
            ):
                delete += dedent(
                    """
                    if (tryNamedDelete) {
                      bool hasOnProto;
                      if (!HasPropertyOnPrototype(cx, proxy, id, &hasOnProto)) {
                        return false;
                      }
                      tryNamedDelete = !hasOnProto;
                    }
                    """
                )

            # We always return above for an index id in the case when we support
            # indexed properties, so we can just treat the id as a name
            # unconditionally here.
            delete += fill(
                """
                if (tryNamedDelete) {
                  bool found = false;
                  bool deleteSucceeded;
                  $*{namedBody}
                  if (found) {
                    return deleteSucceeded ? opresult.succeed() : opresult.failCantDelete();
                  }
                }
                """,
                namedBody=namedBody,
            )

        delete += dedent(
            """

            return dom::DOMProxyHandler::delete_(cx, proxy, id, opresult);
            """
        )

        return delete


class CGDOMJSProxyHandler_ownPropNames(ClassMethod):
    def __init__(
        self,
        descriptor,
    ):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("unsigned", "flags"),
            Argument("JS::MutableHandleVector<jsid>", "props"),
        ]
        ClassMethod.__init__(
            self, "ownPropNames", "bool", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        if self.descriptor.isMaybeCrossOriginObject():
            xrayDecl = dedent(
                """
                MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy));
                if (!IsPlatformObjectSameOrigin(cx, proxy)) {
                  if (!(flags & JSITER_HIDDEN)) {
                    // There are no enumerable cross-origin props, so we're done.
                    return true;
                  }

                  JS::Rooted<JSObject*> holder(cx);
                  if (!EnsureHolder(cx, proxy, &holder)) {
                    return false;
                  }

                  if (!js::GetPropertyKeys(cx, holder, flags, props)) {
                    return false;
                  }

                  return xpc::AppendCrossOriginWhitelistedPropNames(cx, props);
                }

                """
            )
            xrayCheck = ""
        else:
            xrayDecl = "bool isXray = xpc::WrapperFactory::IsXrayWrapper(proxy);\n"
            xrayCheck = "!isXray &&"

        # Per spec, we do indices, then named props, then everything else.
        if self.descriptor.supportsIndexedProperties():
            if self.descriptor.lengthNeedsCallerType():
                callerType = callerTypeGetterForDescriptor(self.descriptor)
            else:
                callerType = ""
            addIndices = fill(
                """

                uint32_t length = UnwrapProxy(proxy)->Length(${callerType});
                MOZ_ASSERT(int32_t(length) >= 0);
                for (int32_t i = 0; i < int32_t(length); ++i) {
                  if (!props.append(JS::PropertyKey::Int(i))) {
                    return false;
                  }
                }
                """,
                callerType=callerType,
            )
        else:
            addIndices = ""

        if self.descriptor.supportsNamedProperties():
            if self.descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns"):
                shadow = "!isXray"
            else:
                shadow = "false"

            if self.descriptor.supportedNamesNeedCallerType():
                callerType = ", " + callerTypeGetterForDescriptor(self.descriptor)
            else:
                callerType = ""

            addNames = fill(
                """
                nsTArray<nsString> names;
                UnwrapProxy(proxy)->GetSupportedNames(names${callerType});
                if (!AppendNamedPropertyIds(cx, proxy, names, ${shadow}, props)) {
                  return false;
                }
                """,
                callerType=callerType,
                shadow=shadow,
            )
            if not self.descriptor.namedPropertiesEnumerable:
                addNames = CGIfWrapper(
                    CGGeneric(addNames), "flags & JSITER_HIDDEN"
                ).define()
            addNames = "\n" + addNames
        else:
            addNames = ""

        addExpandoProps = fill(
            """
            JS::Rooted<JSObject*> expando(cx);
            if (${xrayCheck}(expando = DOMProxyHandler::GetExpandoObject(proxy)) &&
                !js::GetPropertyKeys(cx, expando, flags, props)) {
              return false;
            }
            """,
            xrayCheck=xrayCheck,
        )

        if self.descriptor.isMaybeCrossOriginObject():
            # We need to enter our compartment (which we might not be
            # in right now) to get the expando props.
            addExpandoProps = fill(
                """
                {  // Scope for accessing the expando.
                  // Safe to enter our compartment, because IsPlatformObjectSameOrigin tested true.
                  JSAutoRealm ar(cx, proxy);
                  $*{addExpandoProps}
                }
                for (auto& id : props) {
                  JS_MarkCrossZoneId(cx, id);
                }
                """,
                addExpandoProps=addExpandoProps,
            )

        return fill(
            """
            $*{xrayDecl}
            $*{addIndices}
            $*{addNames}

            $*{addExpandoProps}

            return true;
            """,
            xrayDecl=xrayDecl,
            addIndices=addIndices,
            addNames=addNames,
            addExpandoProps=addExpandoProps,
        )


class CGDOMJSProxyHandler_hasOwn(ClassMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("bool*", "bp"),
        ]
        ClassMethod.__init__(
            self, "hasOwn", "bool", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        if self.descriptor.isMaybeCrossOriginObject():
            maybeCrossOrigin = dedent(
                """
                if (!IsPlatformObjectSameOrigin(cx, proxy)) {
                  // Just hand this off to BaseProxyHandler to do the slow-path thing.
                  // The BaseProxyHandler code is OK with this happening without entering the
                  // compartment of "proxy", which is important to get the right answers.
                  return js::BaseProxyHandler::hasOwn(cx, proxy, id, bp);
                }

                // Now safe to enter the Realm of proxy and do the rest of the work there.
                JSAutoRealm ar(cx, proxy);
                JS_MarkCrossZoneId(cx, id);
                """
            )
        else:
            maybeCrossOrigin = ""

        if self.descriptor.supportsIndexedProperties():
            indexed = fill(
                """
                uint32_t index = GetArrayIndexFromId(id);
                if (IsArrayIndex(index)) {
                  bool found = false;
                  $*{presenceChecker}

                  *bp = found;
                  return true;
                }

                """,
                presenceChecker=CGProxyIndexedPresenceChecker(
                    self.descriptor, foundVar="found"
                ).define(),
            )
        else:
            indexed = ""

        if self.descriptor.supportsNamedProperties():
            # If we support indexed properties we always return above for index
            # property names, so no need to check for those here.
            named = fill(
                """
                bool found = false;
                $*{presenceChecker}

                *bp = found;
                """,
                presenceChecker=CGProxyNamedPresenceChecker(
                    self.descriptor, foundVar="found"
                ).define(),
            )
            if not self.descriptor.interface.getExtendedAttribute(
                "LegacyOverrideBuiltIns"
            ):
                named = fill(
                    """
                    bool hasOnProto;
                    if (!HasPropertyOnPrototype(cx, proxy, id, &hasOnProto)) {
                      return false;
                    }
                    if (!hasOnProto) {
                      $*{protoLacksProperty}
                      return true;
                    }
                    """,
                    protoLacksProperty=named,
                )
                named += "*bp = false;\n"
            else:
                named += "\n"
        else:
            named = "*bp = false;\n"

        missingPropUseCounters = missingPropUseCountersForDescriptor(self.descriptor)

        return fill(
            """
            MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy),
                      "Should not have a XrayWrapper here");
            $*{maybeCrossOrigin}
            $*{indexed}

            $*{missingPropUseCounters}
            JS::Rooted<JSObject*> expando(cx, GetExpandoObject(proxy));
            if (expando) {
              bool b = true;
              bool ok = JS_HasPropertyById(cx, expando, id, &b);
              *bp = !!b;
              if (!ok || *bp) {
                return ok;
              }
            }

            $*{named}
            return true;
            """,
            maybeCrossOrigin=maybeCrossOrigin,
            indexed=indexed,
            missingPropUseCounters=missingPropUseCounters,
            named=named,
        )


class CGDOMJSProxyHandler_get(ClassMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<JS::Value>", "receiver"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::MutableHandle<JS::Value>", "vp"),
        ]
        ClassMethod.__init__(
            self, "get", "bool", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        missingPropUseCounters = missingPropUseCountersForDescriptor(self.descriptor)

        getUnforgeableOrExpando = dedent(
            """
            bool expandoHasProp = false;
            { // Scope for expando
              JS::Rooted<JSObject*> expando(cx, DOMProxyHandler::GetExpandoObject(proxy));
              if (expando) {
                if (!JS_HasPropertyById(cx, expando, id, &expandoHasProp)) {
                  return false;
                }

                if (expandoHasProp) {
                  // Forward the get to the expando object, but our receiver is whatever our
                  // receiver is.
                  if (!JS_ForwardGetPropertyTo(cx, expando, id, ${receiver}, vp)) {
                    return false;
                  }
                }
              }
            }
            """
        )

        getOnPrototype = dedent(
            """
            bool foundOnPrototype;
            if (!GetPropertyOnPrototype(cx, proxy, ${receiver}, id, &foundOnPrototype, vp)) {
              return false;
            }
            """
        )

        if self.descriptor.isMaybeCrossOriginObject():
            # We can't handle these for cross-origin objects
            assert not self.descriptor.supportsIndexedProperties()
            assert not self.descriptor.supportsNamedProperties()

            return fill(
                """
                MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy),
                            "Should not have a XrayWrapper here");

                if (!IsPlatformObjectSameOrigin(cx, proxy)) {
                  return CrossOriginGet(cx, proxy, receiver, id, vp);
                }

                $*{missingPropUseCounters}
                { // Scope for the JSAutoRealm accessing expando and prototype.
                  JSAutoRealm ar(cx, proxy);
                  JS::Rooted<JS::Value> wrappedReceiver(cx, receiver);
                  if (!MaybeWrapValue(cx, &wrappedReceiver)) {
                    return false;
                  }
                  JS_MarkCrossZoneId(cx, id);

                  $*{getUnforgeableOrExpando}
                  if (!expandoHasProp) {
                    $*{getOnPrototype}
                    if (!foundOnPrototype) {
                      MOZ_ASSERT(vp.isUndefined());
                      return true;
                    }
                  }
                }

                return MaybeWrapValue(cx, vp);
                """,
                missingPropUseCounters=missingPropUseCountersForDescriptor(
                    self.descriptor
                ),
                getUnforgeableOrExpando=fill(
                    getUnforgeableOrExpando, receiver="wrappedReceiver"
                ),
                getOnPrototype=fill(getOnPrototype, receiver="wrappedReceiver"),
            )

        templateValues = {"jsvalRef": "vp", "jsvalHandle": "vp", "obj": "proxy"}

        getUnforgeableOrExpando = fill(
            getUnforgeableOrExpando, receiver="receiver"
        ) + dedent(
            """

            if (expandoHasProp) {
              return true;
            }
            """
        )
        if self.descriptor.supportsIndexedProperties():
            getIndexedOrExpando = fill(
                """
                uint32_t index = GetArrayIndexFromId(id);
                if (IsArrayIndex(index)) {
                  $*{callGetter}
                  // Even if we don't have this index, we don't forward the
                  // get on to our expando object.
                } else {
                  $*{getUnforgeableOrExpando}
                }
                """,
                callGetter=CGProxyIndexedGetter(
                    self.descriptor, templateValues
                ).define(),
                getUnforgeableOrExpando=getUnforgeableOrExpando,
            )
        else:
            getIndexedOrExpando = getUnforgeableOrExpando

        if self.descriptor.supportsNamedProperties():
            getNamed = CGProxyNamedGetter(self.descriptor, templateValues)
            if self.descriptor.supportsIndexedProperties():
                getNamed = CGIfWrapper(getNamed, "!IsArrayIndex(index)")
            getNamed = getNamed.define() + "\n"
        else:
            getNamed = ""

        getOnPrototype = fill(getOnPrototype, receiver="receiver") + dedent(
            """

            if (foundOnPrototype) {
              return true;
            }

            MOZ_ASSERT(vp.isUndefined());
            """
        )

        if self.descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns"):
            getNamedOrOnPrototype = getNamed + getOnPrototype
        else:
            getNamedOrOnPrototype = getOnPrototype + getNamed

        return fill(
            """
            MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy),
                        "Should not have a XrayWrapper here");

            $*{missingPropUseCounters}
            $*{indexedOrExpando}

            $*{namedOrOnPropotype}
            return true;
            """,
            missingPropUseCounters=missingPropUseCounters,
            indexedOrExpando=getIndexedOrExpando,
            namedOrOnPropotype=getNamedOrOnPrototype,
        )


class CGDOMJSProxyHandler_setCustom(ClassMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx_"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::Handle<JS::Value>", "v"),
            Argument("bool*", "done"),
        ]
        ClassMethod.__init__(
            self, "setCustom", "bool", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        assertion = (
            "MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy),\n"
            '           "Should not have a XrayWrapper here");\n'
        )

        # Correctness first. If we have a NamedSetter and [LegacyOverrideBuiltIns],
        # always call the NamedSetter and never do anything else.
        namedSetter = self.descriptor.operations["NamedSetter"]
        if namedSetter is not None and self.descriptor.interface.getExtendedAttribute(
            "LegacyOverrideBuiltIns"
        ):
            # Check assumptions.
            if self.descriptor.supportsIndexedProperties():
                raise ValueError(
                    "In interface "
                    + self.descriptor.name
                    + ": "
                    + "Can't cope with [LegacyOverrideBuiltIns] and an indexed getter"
                )
            if self.descriptor.hasLegacyUnforgeableMembers:
                raise ValueError(
                    "In interface "
                    + self.descriptor.name
                    + ": "
                    + "Can't cope with [LegacyOverrideBuiltIns] and unforgeable members"
                )

            tailCode = dedent(
                """
                *done = true;
                return true;
                """
            )
            callSetter = CGProxyNamedSetter(
                self.descriptor, tailCode, argumentHandleValue="v"
            )
            error_label = CGSpecializedMethod.error_reporting_label_helper(
                self.descriptor, namedSetter, isConstructor=False
            )
            if error_label:
                cxDecl = fill(
                    """
                    BindingCallContext cx(cx_, ${error_label});
                    """,
                    error_label=error_label,
                )
            else:
                cxDecl = dedent(
                    """
                    JSContext* cx = cx_;
                    """
                )
            return fill(
                """
                $*{assertion}
                $*{cxDecl}
                $*{callSetter}
                *done = false;
                return true;
                """,
                assertion=assertion,
                cxDecl=cxDecl,
                callSetter=callSetter.define(),
            )

        # As an optimization, if we are going to call an IndexedSetter, go
        # ahead and call it and have done.
        indexedSetter = self.descriptor.operations["IndexedSetter"]
        if indexedSetter is not None:
            error_label = CGSpecializedMethod.error_reporting_label_helper(
                self.descriptor, indexedSetter, isConstructor=False
            )
            if error_label:
                cxDecl = fill(
                    """
                    BindingCallContext cx(cx_, ${error_label});
                    """,
                    error_label=error_label,
                )
            else:
                cxDecl = dedent(
                    """
                    JSContext* cx = cx_;
                    """
                )
            setIndexed = fill(
                """
                uint32_t index = GetArrayIndexFromId(id);
                if (IsArrayIndex(index)) {
                  $*{cxDecl}
                  $*{callSetter}
                  *done = true;
                  return true;
                }

                """,
                cxDecl=cxDecl,
                callSetter=CGProxyIndexedSetter(
                    self.descriptor, argumentHandleValue="v"
                ).define(),
            )
        else:
            setIndexed = ""

        return assertion + setIndexed + "*done = false;\n" "return true;\n"


class CGDOMJSProxyHandler_className(ClassMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
        ]
        ClassMethod.__init__(
            self,
            "className",
            "const char*",
            args,
            virtual=True,
            override=True,
            const=True,
        )
        self.descriptor = descriptor

    def getBody(self):
        if self.descriptor.isMaybeCrossOriginObject():
            crossOrigin = dedent(
                """
                if (!IsPlatformObjectSameOrigin(cx, proxy)) {
                  return "Object";
                }

                """
            )
        else:
            crossOrigin = ""
        return fill(
            """
            $*{crossOrigin}
            return "${name}";
            """,
            crossOrigin=crossOrigin,
            name=self.descriptor.name,
        )


class CGDOMJSProxyHandler_trace(ClassMethod):
    def __init__(self, descriptor):
        args = [Argument("JSTracer*", "trc"), Argument("JSObject*", "proxy")]
        ClassMethod.__init__(
            self,
            "trace",
            "void",
            args,
            virtual=True,
            override=True,
            const=True,
        )
        self.descriptor = descriptor

    def getBody(self):
        iface = getReflectedHTMLAttributesIface(self.descriptor)
        return fill(
            """
            ${reflectedAttributesBase}::ReflectedHTMLAttributeSlots::Trace(${trc}, ${proxy});
            return Base::trace(${trc}, ${proxy});
            """,
            reflectedAttributesBase=toBindingNamespace(iface.identifier.name),
            trc=self.args[0].name,
            proxy=self.args[1].name,
        )


class CGDOMJSProxyHandler_finalizeInBackground(ClassMethod):
    def __init__(self, descriptor):
        args = [Argument("const JS::Value&", "priv")]
        ClassMethod.__init__(
            self,
            "finalizeInBackground",
            "bool",
            args,
            virtual=True,
            override=True,
            const=True,
        )
        self.descriptor = descriptor

    def getBody(self):
        return "return false;\n"


class CGDOMJSProxyHandler_finalize(ClassMethod):
    def __init__(self, descriptor):
        args = [Argument("JS::GCContext*", "gcx"), Argument("JSObject*", "proxy")]
        ClassMethod.__init__(
            self, "finalize", "void", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        return (
            "%s* self = UnwrapPossiblyNotInitializedDOMObject<%s>(proxy);\n"
            % (self.descriptor.nativeType, self.descriptor.nativeType)
        ) + finalizeHook(
            self.descriptor,
            FINALIZE_HOOK_NAME,
            self.args[0].name,
            self.args[1].name,
        ).define()


class CGDOMJSProxyHandler_objectMoved(ClassMethod):
    def __init__(self, descriptor):
        args = [Argument("JSObject*", "obj"), Argument("JSObject*", "old")]
        ClassMethod.__init__(
            self, "objectMoved", "size_t", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        return (
            "%s* self = UnwrapPossiblyNotInitializedDOMObject<%s>(obj);\n"
            % (self.descriptor.nativeType, self.descriptor.nativeType)
        ) + objectMovedHook(
            self.descriptor,
            OBJECT_MOVED_HOOK_NAME,
            self.args[0].name,
            self.args[1].name,
        )


class CGDOMJSProxyHandler_getElements(ClassMethod):
    def __init__(self, descriptor):
        assert descriptor.supportsIndexedProperties()

        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("uint32_t", "begin"),
            Argument("uint32_t", "end"),
            Argument("js::ElementAdder*", "adder"),
        ]
        ClassMethod.__init__(
            self, "getElements", "bool", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        # Just like ownPropertyKeys we'll assume that we have no holes, so
        # we have all properties from 0 to length.  If that ever changes
        # (unlikely), we'll need to do something a bit more clever with how we
        # forward on to our ancestor.

        templateValues = {
            "jsvalRef": "temp",
            "jsvalHandle": "&temp",
            "obj": "proxy",
            "successCode": (
                "if (!adder->append(cx, temp)) return false;\n" "continue;\n"
            ),
        }
        get = CGProxyIndexedGetter(
            self.descriptor, templateValues, False, False
        ).define()

        if self.descriptor.lengthNeedsCallerType():
            callerType = callerTypeGetterForDescriptor(self.descriptor)
        else:
            callerType = ""

        return fill(
            """
            JS::Rooted<JS::Value> temp(cx);
            MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy),
                       "Should not have a XrayWrapper here");

            ${nativeType}* self = UnwrapProxy(proxy);
            uint32_t length = self->Length(${callerType});
            // Compute the end of the indices we'll get ourselves
            uint32_t ourEnd = std::clamp(length, begin, end);

            for (uint32_t index = begin; index < ourEnd; ++index) {
              $*{get}
            }

            if (end > ourEnd) {
              JS::Rooted<JSObject*> proto(cx);
              if (!js::GetObjectProto(cx, proxy, &proto)) {
                return false;
              }
              return js::GetElementsWithAdder(cx, proto, proxy, ourEnd, end, adder);
            }

            return true;
            """,
            nativeType=self.descriptor.nativeType,
            callerType=callerType,
            get=get,
        )


class CGJSProxyHandler_getInstance(ClassMethod):
    def __init__(self, type):
        self.type = type
        ClassMethod.__init__(
            self, "getInstance", "const %s*" % self.type, [], static=True
        )

    def getBody(self):
        return fill(
            """
            static const ${type} instance;
            return &instance;
            """,
            type=self.type,
        )


class CGDOMJSProxyHandler_call(ClassMethod):
    def __init__(self):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("const JS::CallArgs&", "args"),
        ]

        ClassMethod.__init__(
            self, "call", "bool", args, virtual=True, override=True, const=True
        )

    def getBody(self):
        return fill(
            """
            return js::ForwardToNative(cx, ${legacyCaller}, args);
            """,
            legacyCaller=LEGACYCALLER_HOOK_NAME,
        )


class CGDOMJSProxyHandler_isCallable(ClassMethod):
    def __init__(self):
        ClassMethod.__init__(
            self,
            "isCallable",
            "bool",
            [Argument("JSObject*", "obj")],
            virtual=True,
            override=True,
            const=True,
        )

    def getBody(self):
        return dedent(
            """
            return true;
        """
        )


class CGDOMJSProxyHandler_canNurseryAllocate(ClassMethod):
    """
    Override the default canNurseryAllocate in BaseProxyHandler, for cases when
    we should be nursery-allocated.
    """

    def __init__(self):
        ClassMethod.__init__(
            self,
            "canNurseryAllocate",
            "bool",
            [],
            virtual=True,
            override=True,
            const=True,
        )

    def getBody(self):
        return dedent(
            """
            return true;
        """
        )


class CGDOMJSProxyHandler_getOwnPropertyDescriptor(ClassMethod):
    """
    Implementation of getOwnPropertyDescriptor.  We only use this for
    cross-origin objects.
    """

    def __init__(self, descriptor):
        assert descriptor.isMaybeCrossOriginObject()

        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::MutableHandle<Maybe<JS::PropertyDescriptor>>", "desc"),
        ]
        ClassMethod.__init__(
            self,
            "getOwnPropertyDescriptor",
            "bool",
            args,
            virtual=True,
            override=True,
            const=True,
        )
        self.descriptor = descriptor

    def getBody(self):
        return dedent(
            """
            // Implementation of <https://html.spec.whatwg.org/multipage/history.html#location-getownproperty>.
            MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy));

            // Step 1.
            if (IsPlatformObjectSameOrigin(cx, proxy)) {
              { // Scope so we can wrap our PropertyDescriptor back into
                // the caller compartment.
                // Enter the Realm of "proxy" so we can work with it.
                JSAutoRealm ar(cx, proxy);

                JS_MarkCrossZoneId(cx, id);

                // The spec messes around with configurability of the returned
                // descriptor here, but it's not clear what should actually happen
                // here.  See <https://github.com/whatwg/html/issues/4157>.  For
                // now, keep our old behavior and don't do any magic.
                if (!dom::DOMProxyHandler::getOwnPropertyDescriptor(cx, proxy, id, desc)) {
                  return false;
                }
              }
              return JS_WrapPropertyDescriptor(cx, desc);
            }

            // Step 2.
            if (!CrossOriginGetOwnPropertyHelper(cx, proxy, id, desc)) {
              return false;
            }

            // Step 3.
            if (desc.isSome()) {
              return true;
            }

            // And step 4.
            return CrossOriginPropertyFallback(cx, proxy, id, desc);
            """
        )


class CGDOMJSProxyHandler_getSameOriginPrototype(ClassMethod):
    """
    Implementation of getSameOriginPrototype.  We only use this for
    cross-origin objects.
    """

    def __init__(self, descriptor):
        assert descriptor.isMaybeCrossOriginObject()

        args = [Argument("JSContext*", "cx")]
        ClassMethod.__init__(
            self,
            "getSameOriginPrototype",
            "JSObject*",
            args,
            virtual=True,
            override=True,
            const=True,
        )
        self.descriptor = descriptor

    def getBody(self):
        return dedent(
            """
            return GetProtoObjectHandle(cx);
            """
        )


class CGDOMJSProxyHandler_definePropertySameOrigin(ClassMethod):
    """
    Implementation of definePropertySameOrigin.  We only use this for
    cross-origin objects.
    """

    def __init__(self, descriptor):
        assert descriptor.isMaybeCrossOriginObject()

        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::Handle<JS::PropertyDescriptor>", "desc"),
            Argument("JS::ObjectOpResult&", "result"),
        ]
        ClassMethod.__init__(
            self,
            "definePropertySameOrigin",
            "bool",
            args,
            virtual=True,
            override=True,
            const=True,
        )
        self.descriptor = descriptor

    def getBody(self):
        return dedent(
            """
            return dom::DOMProxyHandler::defineProperty(cx, proxy, id, desc, result);
            """
        )


class CGDOMJSProxyHandler_set(ClassMethod):
    """
    Implementation of set().  We only use this for cross-origin objects.
    """

    def __init__(self, descriptor):
        assert descriptor.isMaybeCrossOriginObject()

        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::Handle<JS::Value>", "v"),
            Argument("JS::Handle<JS::Value>", "receiver"),
            Argument("JS::ObjectOpResult&", "result"),
        ]
        ClassMethod.__init__(
            self, "set", "bool", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        return dedent(
            """
            if (!IsPlatformObjectSameOrigin(cx, proxy)) {
              return CrossOriginSet(cx, proxy, id, v, receiver, result);
            }

            // Safe to enter the Realm of proxy now, since it's same-origin with us.
            JSAutoRealm ar(cx, proxy);
            JS::Rooted<JS::Value> wrappedReceiver(cx, receiver);
            if (!MaybeWrapValue(cx, &wrappedReceiver)) {
              return false;
            }

            JS::Rooted<JS::Value> wrappedValue(cx, v);
            if (!MaybeWrapValue(cx, &wrappedValue)) {
              return false;
            }

            JS_MarkCrossZoneId(cx, id);

            return dom::DOMProxyHandler::set(cx, proxy, id, wrappedValue, wrappedReceiver, result);
            """
        )


class CGDOMJSProxyHandler_EnsureHolder(ClassMethod):
    """
    Implementation of EnsureHolder().  We only use this for cross-origin objects.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "proxy"),
            Argument("JS::MutableHandle<JSObject*>", "holder"),
        ]
        ClassMethod.__init__(
            self, "EnsureHolder", "bool", args, virtual=True, override=True, const=True
        )
        self.descriptor = descriptor

    def getBody(self):
        return dedent(
            """
            return EnsureHolder(cx, proxy,
                                JSCLASS_RESERVED_SLOTS(JS::GetClass(proxy)) - 1,
                                sCrossOriginProperties, holder);
            """
        )


class CGDOMJSProxyHandler(CGClass):
    def __init__(self, descriptor):
        assert (
            descriptor.supportsIndexedProperties()
            or descriptor.supportsNamedProperties()
            or descriptor.isMaybeCrossOriginObject()
        )

        if descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns"):
            assert not descriptor.isMaybeCrossOriginObject()
            parentClass = "ShadowingDOMProxyHandler"
        elif descriptor.isMaybeCrossOriginObject():
            parentClass = "MaybeCrossOriginObject<mozilla::dom::DOMProxyHandler>"
        else:
            parentClass = "mozilla::dom::DOMProxyHandler"

        typeAliases = [
            ClassUsingDeclaration("Base", parentClass),
        ]
        methods = [
            CGDOMJSProxyHandler_getOwnPropDescriptor(descriptor),
            CGDOMJSProxyHandler_defineProperty(descriptor),
            ClassUsingFromBaseDeclaration(
                "mozilla::dom::DOMProxyHandler", "defineProperty"
            ),
            CGDOMJSProxyHandler_ownPropNames(descriptor),
            CGDOMJSProxyHandler_hasOwn(descriptor),
            CGDOMJSProxyHandler_get(descriptor),
            CGDOMJSProxyHandler_className(descriptor),
            CGDOMJSProxyHandler_finalizeInBackground(descriptor),
            CGDOMJSProxyHandler_finalize(descriptor),
            CGJSProxyHandler_getInstance("DOMProxyHandler"),
            CGDOMJSProxyHandler_delete(descriptor),
        ]
        if getReflectedHTMLAttributesIface(descriptor):
            methods.append(CGDOMJSProxyHandler_trace(descriptor))
        constructors = [
            ClassConstructor([], constexpr=True, visibility="public", explicit=True)
        ]

        if descriptor.supportsIndexedProperties():
            methods.append(CGDOMJSProxyHandler_getElements(descriptor))
        if descriptor.operations["IndexedSetter"] is not None or (
            descriptor.operations["NamedSetter"] is not None
            and descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns")
        ):
            methods.append(CGDOMJSProxyHandler_setCustom(descriptor))
        if descriptor.operations["LegacyCaller"]:
            methods.append(CGDOMJSProxyHandler_call())
            methods.append(CGDOMJSProxyHandler_isCallable())
        if descriptor.interface.hasProbablyShortLivingWrapper():
            if not descriptor.wrapperCache:
                raise TypeError(
                    "Need a wrapper cache to support nursery "
                    "allocation of DOM objects"
                )
            methods.append(CGDOMJSProxyHandler_canNurseryAllocate())
        if descriptor.wrapperCache:
            methods.append(CGDOMJSProxyHandler_objectMoved(descriptor))

        if descriptor.isMaybeCrossOriginObject():
            methods.extend(
                [
                    CGDOMJSProxyHandler_getOwnPropertyDescriptor(descriptor),
                    CGDOMJSProxyHandler_getSameOriginPrototype(descriptor),
                    CGDOMJSProxyHandler_definePropertySameOrigin(descriptor),
                    CGDOMJSProxyHandler_set(descriptor),
                    CGDOMJSProxyHandler_EnsureHolder(descriptor),
                    ClassUsingFromBaseDeclaration(
                        "MaybeCrossOriginObjectMixins", "EnsureHolder"
                    ),
                ]
            )

        CGClass.__init__(
            self,
            "DOMProxyHandler",
            bases=[ClassBase(parentClass)],
            typeAliases=typeAliases,
            constructors=constructors,
            methods=methods,
        )


class CGDOMJSProxyHandlerDeclarer(CGThing):
    """
    A class for declaring a DOMProxyHandler.
    """

    def __init__(self, handlerThing):
        self.handlerThing = handlerThing

    def declare(self):
        # Our class declaration should happen when we're defining
        return ""

    def define(self):
        return self.handlerThing.declare()


class CGDOMJSProxyHandlerDefiner(CGThing):
    """
    A class for defining a DOMProxyHandler.
    """

    def __init__(self, handlerThing):
        self.handlerThing = handlerThing

    def declare(self):
        return ""

    def define(self):
        return self.handlerThing.define()


def stripTrailingWhitespace(text):
    tail = "\n" if text.endswith("\n") else ""
    lines = text.splitlines()
    return "\n".join(line.rstrip() for line in lines) + tail


class MemberProperties:
    def __init__(self):
        self.isCrossOriginMethod = False
        self.isCrossOriginGetter = False
        self.isCrossOriginSetter = False


def memberProperties(m, descriptor):
    props = MemberProperties()
    if m.isMethod():
        if not m.isIdentifierLess() or m == descriptor.operations["Stringifier"]:
            if not m.isStatic() and descriptor.interface.hasInterfacePrototypeObject():
                if m.getExtendedAttribute("CrossOriginCallable"):
                    props.isCrossOriginMethod = True
    elif m.isAttr():
        if not m.isStatic() and descriptor.interface.hasInterfacePrototypeObject():
            if m.getExtendedAttribute("CrossOriginReadable"):
                props.isCrossOriginGetter = True
        if not m.readonly:
            if not m.isStatic() and descriptor.interface.hasInterfacePrototypeObject():
                if m.getExtendedAttribute("CrossOriginWritable"):
                    props.isCrossOriginSetter = True
        elif m.getExtendedAttribute("PutForwards"):
            if m.getExtendedAttribute("CrossOriginWritable"):
                props.isCrossOriginSetter = True
        elif m.getExtendedAttribute("Replaceable") or m.getExtendedAttribute(
            "LegacyLenientSetter"
        ):
            if m.getExtendedAttribute("CrossOriginWritable"):
                props.isCrossOriginSetter = True

    return props


class CGDescriptor(CGThing):
    def __init__(self, descriptor, attributeTemplates):
        CGThing.__init__(self)

        assert (
            not descriptor.concrete
            or descriptor.interface.hasInterfacePrototypeObject()
            or descriptor.hasOrdinaryObjectPrototype()
        )

        self._deps = descriptor.interface.getDeps()

        iteratorCGThings = None
        if (
            descriptor.interface.isIterable()
            and descriptor.interface.maplikeOrSetlikeOrIterable.isPairIterator()
        ) or descriptor.interface.isAsyncIterable():
            # We need the Wrap function when using the [Async]IterableIterator type, so we want to declare it before we need it. We don't really want to expose it in the header file, so we make it static too.
            iteratorCGThings = []
            itr_iface = (
                descriptor.interface.maplikeOrSetlikeOrIterable.iteratorType.inner
            )
            iteratorDescriptor = descriptor.getDescriptor(itr_iface.identifier.name)
            iteratorCGThings.append(
                CGWrapNonWrapperCacheMethod(
                    iteratorDescriptor, static=True, signatureOnly=True
                )
            )
            iteratorCGThings = CGList(
                (CGIndenter(t, declareOnly=True) for t in iteratorCGThings), "\n"
            )
            iteratorCGThings = CGWrapper(iteratorCGThings, pre="\n", post="\n")
            iteratorCGThings = CGWrapper(
                CGNamespace(
                    toBindingNamespace(iteratorDescriptor.name), iteratorCGThings
                ),
                post="\n",
            )

        cgThings = []

        isIteratorInterface = (
            descriptor.interface.isIteratorInterface()
            or descriptor.interface.isAsyncIteratorInterface()
        )
        if not isIteratorInterface:
            cgThings.append(
                CGGeneric(declare="typedef %s NativeType;\n" % descriptor.nativeType)
            )
            parent = descriptor.interface.parent
            if parent:
                cgThings.append(
                    CGGeneric(
                        "static_assert(IsRefcounted<NativeType>::value == IsRefcounted<%s::NativeType>::value,\n"
                        '              "Can\'t inherit from an interface with a different ownership model.");\n'
                        % toBindingNamespace(descriptor.parentPrototypeName)
                    )
                )

        defaultToJSONMethod = None
        needCrossOriginPropertyArrays = False
        unscopableNames = list()

        for n in descriptor.interface.legacyFactoryFunctions:
            cgThings.append(
                CGClassConstructor(descriptor, n, LegacyFactoryFunctionName(n))
            )

        if descriptor.attributeTemplates is not None:
            for template in descriptor.attributeTemplates:
                if template.getter is not None:
                    cgThings.append(
                        CGTemplateForSpecializedGetter(descriptor, template)
                    )
                if template.setter is not None:
                    cgThings.append(
                        CGTemplateForSpecializedSetter(descriptor, template)
                    )

        if descriptor.interface.reflectedHTMLAttributesReturningFrozenArray:
            cgThings.append(CGDefineHTMLAttributeSlots(descriptor))

        for m in descriptor.interface.members:
            if m.isMethod() and m.identifier.name == "QueryInterface":
                continue

            props = memberProperties(m, descriptor)

            if m.isMethod():
                if m.getExtendedAttribute("Unscopable"):
                    assert not m.isStatic()
                    unscopableNames.append(m.identifier.name)
                if m.isDefaultToJSON():
                    defaultToJSONMethod = m
                elif (
                    not m.isIdentifierLess()
                    or m == descriptor.operations["Stringifier"]
                ):
                    if m.isStatic():
                        assert descriptor.interface.hasInterfaceObject()
                        cgThings.append(CGStaticMethod(descriptor, m))
                        if m.returnsPromise():
                            cgThings.append(CGStaticMethodJitinfo(m))
                    elif descriptor.interface.hasInterfacePrototypeObject():
                        specializedMethod = CGSpecializedMethod(descriptor, m)
                        cgThings.append(specializedMethod)
                        if m.returnsPromise():
                            cgThings.append(
                                CGMethodPromiseWrapper(descriptor, specializedMethod)
                            )
                        cgThings.append(CGMemberJITInfo(descriptor, m))
                        if props.isCrossOriginMethod:
                            needCrossOriginPropertyArrays = True
            # If we've hit the maplike/setlike member itself, go ahead and
            # generate its convenience functions.
            elif m.isMaplikeOrSetlike():
                cgThings.append(CGMaplikeOrSetlikeHelperGenerator(descriptor, m))
            elif m.isAttr():
                if m.type.isObservableArray():
                    cgThings.append(
                        CGObservableArrayProxyHandlerGenerator(descriptor, m)
                    )
                    cgThings.append(CGObservableArrayHelperGenerator(descriptor, m))
                if m.getExtendedAttribute("Unscopable"):
                    assert not m.isStatic()
                    unscopableNames.append(m.identifier.name)
                if m.isStatic():
                    assert descriptor.interface.hasInterfaceObject()
                    cgThings.append(CGStaticGetter(descriptor, m))
                elif descriptor.interface.hasInterfacePrototypeObject():
                    template = m.getExtendedAttribute("BindingTemplate")
                    if template is not None:
                        templateName = template[0][0]
                        additionalArg = template[0][1]
                        if not (m.type.isPrimitive() or m.type.isString()):
                            raise TypeError(
                                "We only support primitives or strings on templated attributes. "
                                "Attribute '%s' on interface '%s' has type '%s' but tries to "
                                "use template '%s'"
                                % (
                                    m.identifier.name,
                                    descriptor.interface.identifier.name,
                                    m.type,
                                    templateName,
                                )
                            )
                        template = attributeTemplates.get(templateName)
                        specializedGetter = CGSpecializedTemplatedGetter(
                            descriptor, m, template, additionalArg
                        )
                    else:
                        specializedGetter = CGSpecializedGetter(descriptor, m)
                    cgThings.append(specializedGetter)
                    if m.type.isPromise():
                        cgThings.append(
                            CGGetterPromiseWrapper(descriptor, specializedGetter)
                        )
                    if props.isCrossOriginGetter:
                        needCrossOriginPropertyArrays = True
                if not m.readonly:
                    if m.isStatic():
                        assert descriptor.interface.hasInterfaceObject()
                        cgThings.append(CGStaticSetter(descriptor, m))
                    elif descriptor.interface.hasInterfacePrototypeObject():
                        template = m.getExtendedAttribute("BindingTemplate")
                        if template is not None:
                            if isinstance(template[0], list):
                                templateName = template[0][0]
                                additionalArg = template[0][1]
                            else:
                                templateName = template[0]
                                additionalArg = None
                            template = attributeTemplates.get(templateName)
                            specializedSetter = CGSpecializedTemplatedSetter(
                                descriptor, m, template, additionalArg
                            )
                        else:
                            specializedSetter = CGSpecializedSetter(descriptor, m)
                        cgThings.append(specializedSetter)
                        if props.isCrossOriginSetter:
                            needCrossOriginPropertyArrays = True
                elif m.getExtendedAttribute("PutForwards"):
                    cgThings.append(CGSpecializedForwardingSetter(descriptor, m))
                    if props.isCrossOriginSetter:
                        needCrossOriginPropertyArrays = True
                elif m.getExtendedAttribute("Replaceable"):
                    cgThings.append(CGSpecializedReplaceableSetter(descriptor, m))
                elif m.getExtendedAttribute("LegacyLenientSetter"):
                    # XXX In this case, we need to add an include for mozilla/dom/Document.h to the generated cpp file.
                    cgThings.append(CGSpecializedLenientSetter(descriptor, m))
                if (
                    not m.isStatic()
                    and descriptor.interface.hasInterfacePrototypeObject()
                ):
                    cgThings.append(CGMemberJITInfo(descriptor, m))
            if m.isConst() and m.type.isPrimitive():
                cgThings.append(CGConstDefinition(m))

        if defaultToJSONMethod:
            cgThings.append(CGDefaultToJSONMethod(descriptor, defaultToJSONMethod))
            cgThings.append(CGMemberJITInfo(descriptor, defaultToJSONMethod))

        if descriptor.concrete and not descriptor.proxy:
            if wantsAddProperty(descriptor):
                cgThings.append(CGAddPropertyHook(descriptor))

            # Always have a finalize hook, regardless of whether the class
            # wants a custom hook.
            cgThings.append(CGClassFinalizeHook(descriptor))

        if wantsGetWrapperCache(descriptor):
            cgThings.append(CGGetWrapperCacheHook(descriptor))

        if descriptor.concrete and descriptor.wrapperCache and not descriptor.proxy:
            cgThings.append(CGClassObjectMovedHook(descriptor))

        properties = PropertyArrays(descriptor)
        cgThings.append(CGGeneric(define=str(properties)))
        cgThings.append(CGNativeProperties(descriptor, properties))

        if defaultToJSONMethod:
            # Now that we know about our property arrays, we can
            # output our "collect attribute values" method, which uses those.
            cgThings.append(
                CGCollectJSONAttributesMethod(descriptor, defaultToJSONMethod)
            )

        # Declare our DOMProxyHandler.
        if descriptor.concrete and descriptor.proxy:
            cgThings.append(
                CGGeneric(
                    fill(
                        """
                        static_assert(std::is_base_of_v<nsISupports, ${nativeType}>,
                                      "We don't support non-nsISupports native classes for "
                                      "proxy-based bindings yet");

                        """,
                        nativeType=descriptor.nativeType,
                    )
                )
            )
            if not descriptor.wrapperCache:
                raise TypeError(
                    "We need a wrappercache to support expandos for proxy-based "
                    "bindings (" + descriptor.name + ")"
                )
            handlerThing = CGDOMJSProxyHandler(descriptor)
            cgThings.append(CGDOMJSProxyHandlerDeclarer(handlerThing))
            cgThings.append(CGProxyIsProxy(descriptor))
            cgThings.append(CGProxyUnwrap(descriptor))

        # Set up our Xray callbacks as needed.  This needs to come
        # after we have our DOMProxyHandler defined.
        if descriptor.wantsXrays:
            if descriptor.concrete and descriptor.proxy:
                if descriptor.needsXrayNamedDeleterHook():
                    cgThings.append(CGDeleteNamedProperty(descriptor))
            elif descriptor.needsXrayResolveHooks():
                cgThings.append(CGResolveOwnPropertyViaResolve(descriptor))
                cgThings.append(
                    CGEnumerateOwnPropertiesViaGetOwnPropertyNames(descriptor)
                )
            if descriptor.wantsXrayExpandoClass:
                cgThings.append(CGXrayExpandoJSClass(descriptor))

            # Now that we have our ResolveOwnProperty/EnumerateOwnProperties stuff
            # done, set up our NativePropertyHooks.
            cgThings.append(CGNativePropertyHooks(descriptor, properties))

        if descriptor.interface.isNamespace():
            cgThings.append(CGNamespaceObjectJSClass(descriptor))
        elif descriptor.interface.hasInterfaceObject():
            cgThings.append(CGClassConstructor(descriptor, descriptor.interface.ctor()))
            cgThings.append(CGInterfaceObjectInfo(descriptor))
            cgThings.append(CGLegacyFactoryFunctions(descriptor))

        cgThings.append(CGLegacyCallHook(descriptor))
        if descriptor.interface.getExtendedAttribute("NeedResolve"):
            cgThings.append(CGResolveHook(descriptor))
            cgThings.append(CGMayResolveHook(descriptor))
            cgThings.append(CGEnumerateHook(descriptor))

        if descriptor.hasNamedPropertiesObject:
            cgThings.append(CGGetNamedPropertiesObjectMethod(descriptor))

        if descriptor.interface.hasInterfacePrototypeObject():
            cgThings.append(CGPrototypeJSClass(descriptor, properties))

        if (
            descriptor.interface.hasInterfaceObject()
            and not descriptor.interface.isExternal()
            and descriptor.isExposedConditionally()
        ):
            cgThings.append(CGConstructorEnabled(descriptor))

        if (
            descriptor.interface.hasMembersInSlots()
            and descriptor.interface.hasChildInterfaces()
        ):
            raise TypeError(
                "We don't support members in slots on "
                "non-leaf interfaces like %s" % descriptor.interface.identifier.name
            )

        if descriptor.needsMissingPropUseCounters:
            cgThings.append(CGCountMaybeMissingProperty(descriptor))

        # CGDOMProxyJSClass/CGDOMJSClass need GetProtoObjectHandle, but we don't
        # want to export it for the iterator interfaces, or if we don't need it
        # for child interfaces or for the named properties object.
        protoObjectHandleGetterIsStatic = descriptor.concrete and (
            isIteratorInterface
            or (
                descriptor.interface.hasInterfacePrototypeObject()
                and not descriptor.interface.hasChildInterfaces()
                and not descriptor.hasNamedPropertiesObject
            )
        )
        if descriptor.concrete:
            if descriptor.interface.isSerializable():
                cgThings.append(CGSerializer(descriptor))
                cgThings.append(CGDeserializer(descriptor))

            if protoObjectHandleGetterIsStatic:
                cgThings.append(
                    CGGetProtoObjectHandleMethod(
                        descriptor, static=True, signatureOnly=True
                    )
                )

            if descriptor.proxy:
                cgThings.append(CGDOMJSProxyHandlerDefiner(handlerThing))
                cgThings.append(CGDOMProxyJSClass(descriptor))
            else:
                cgThings.append(CGDOMJSClass(descriptor))

            if descriptor.interface.hasMembersInSlots():
                cgThings.append(CGUpdateMemberSlotsMethod(descriptor))

            if descriptor.isGlobal():
                assert descriptor.wrapperCache
                cgThings.append(CGWrapGlobalMethod(descriptor, properties))
            elif descriptor.wrapperCache:
                cgThings.append(CGWrapWithCacheMethod(descriptor))
                cgThings.append(CGWrapMethod(descriptor))
            else:
                cgThings.append(
                    CGWrapNonWrapperCacheMethod(descriptor, static=isIteratorInterface)
                )

        # If we're not wrappercached, we don't know how to clear our
        # cached values, since we can't get at the JSObject.
        if descriptor.wrapperCache:
            cgThings.extend(
                CGClearCachedValueMethod(descriptor, m)
                for m in clearableCachedAttrs(descriptor)
            )

        haveUnscopables = (
            len(unscopableNames) != 0
            and descriptor.interface.hasInterfacePrototypeObject()
        )
        if haveUnscopables:
            cgThings.append(
                CGList(
                    [
                        CGGeneric("static const char* const unscopableNames[] = {"),
                        CGIndenter(
                            CGList(
                                [CGGeneric('"%s"' % name) for name in unscopableNames]
                                + [CGGeneric("nullptr")],
                                ",\n",
                            )
                        ),
                        CGGeneric("};\n"),
                    ],
                    "\n",
                )
            )

        legacyWindowAliases = descriptor.interface.legacyWindowAliases
        haveLegacyWindowAliases = len(legacyWindowAliases) != 0
        if haveLegacyWindowAliases:
            cgThings.append(
                CGList(
                    [
                        CGGeneric("static const char* const legacyWindowAliases[] = {"),
                        CGIndenter(
                            CGList(
                                [
                                    CGGeneric('"%s"' % name)
                                    for name in legacyWindowAliases
                                ]
                                + [CGGeneric("nullptr")],
                                ",\n",
                            )
                        ),
                        CGGeneric("};\n"),
                    ],
                    "\n",
                )
            )

        if not descriptor.hasOrdinaryObjectPrototype():
            # CGCreateInterfaceObjectsMethod needs to come after our
            # CGDOMJSClass and unscopables, if any.
            cgThings.append(
                CGCreateInterfaceObjectsMethod(
                    descriptor,
                    properties,
                    haveUnscopables,
                    haveLegacyWindowAliases,
                    static=isIteratorInterface,
                )
            )

            # CGGetProtoObjectMethod and CGGetConstructorObjectMethod need
            # to come after CGCreateInterfaceObjectsMethod.
            if descriptor.interface.hasInterfacePrototypeObject():
                cgThings.append(
                    CGGetProtoObjectHandleMethod(
                        descriptor, static=protoObjectHandleGetterIsStatic
                    )
                )
                if descriptor.interface.hasChildInterfaces():
                    assert not isIteratorInterface
                    cgThings.append(CGGetProtoObjectMethod(descriptor))
            if descriptor.interface.hasInterfaceObject():
                cgThings.append(CGGetConstructorObjectHandleMethod(descriptor))
                cgThings.append(
                    CGCreateAndDefineOnGlobalMethod(
                        descriptor,
                    )
                )

        # See whether we need to generate cross-origin property arrays.
        if needCrossOriginPropertyArrays:
            cgThings.append(CGCrossOriginProperties(descriptor))

        cgThings = CGList((CGIndenter(t, declareOnly=True) for t in cgThings), "\n")
        cgThings = CGWrapper(cgThings, pre="\n", post="\n")
        cgThings = CGWrapper(
            CGNamespace(toBindingNamespace(descriptor.name), cgThings), post="\n"
        )
        self.cgRoot = CGList([iteratorCGThings, cgThings], "\n")

    def declare(self):
        return self.cgRoot.declare()

    def define(self):
        return self.cgRoot.define()

    def deps(self):
        return self._deps


class CGNamespacedEnum(CGThing):
    def __init__(self, namespace, enumName, names, values, comment=""):
        if not values:
            values = []

        # Account for explicit enum values.
        entries = []
        for i in range(0, len(names)):
            if len(values) > i and values[i] is not None:
                entry = "%s = %s" % (names[i], values[i])
            else:
                entry = names[i]
            entries.append(entry)

        # Append a Count.
        entries.append("_" + enumName + "_Count")

        # Indent.
        entries = ["  " + e for e in entries]

        # Build the enum body.
        enumstr = comment + "enum %s : uint16_t\n{\n%s\n};\n" % (
            enumName,
            ",\n".join(entries),
        )
        curr = CGGeneric(declare=enumstr)

        # Add some whitespace padding.
        curr = CGWrapper(curr, pre="\n", post="\n")

        # Add the namespace.
        curr = CGNamespace(namespace, curr)

        # Add the typedef
        typedef = "\ntypedef %s::%s %s;\n\n" % (namespace, enumName, enumName)
        curr = CGList([curr, CGGeneric(declare=typedef)])

        # Save the result.
        self.node = curr

    def declare(self):
        return self.node.declare()

    def define(self):
        return ""


def initIdsClassMethod(identifiers, atomCacheName):
    idinit = [
        '!atomsCache->%s.init(cx, "%s")' % (CGDictionary.makeIdName(id), id)
        for id in identifiers
    ]
    idinit.reverse()
    body = fill(
        """
        MOZ_ASSERT(reinterpret_cast<jsid*>(atomsCache)->isVoid());

        // Initialize these in reverse order so that any failure leaves the first one
        // uninitialized.
        if (${idinit}) {
          return false;
        }
        return true;
        """,
        idinit=" ||\n    ".join(idinit),
    )
    return ClassMethod(
        "InitIds",
        "bool",
        [Argument("JSContext*", "cx"), Argument("%s*" % atomCacheName, "atomsCache")],
        static=True,
        body=body,
        visibility="private",
    )


class CGDictionary(CGThing):
    def __init__(self, dictionary, descriptorProvider):
        self.dictionary = dictionary
        self.descriptorProvider = descriptorProvider
        self.needToInitIds = len(dictionary.members) > 0
        self.memberInfo = [
            (
                member,
                getJSToNativeConversionInfo(
                    member.type,
                    descriptorProvider,
                    isMember="Dictionary",
                    isOptional=member.canHaveMissingValue(),
                    isKnownMissing=not dictionary.needsConversionFromJS,
                    defaultValue=member.defaultValue,
                    sourceDescription=self.getMemberSourceDescription(member),
                ),
            )
            for member in dictionary.members
        ]

        # If we have a union member which is going to be declared in a different
        # header but contains something that will be declared in the same header
        # as us, bail: the C++ includes won't work out.
        for member in dictionary.members:
            type = member.type.unroll()
            if type.isUnion() and CGHeaders.getUnionDeclarationFilename(
                descriptorProvider.getConfig(), type
            ) != CGHeaders.getDeclarationFilename(dictionary):
                for t in type.flatMemberTypes:
                    if t.isDictionary() and CGHeaders.getDeclarationFilename(
                        t.inner
                    ) == CGHeaders.getDeclarationFilename(dictionary):
                        raise TypeError(
                            "Dictionary contains a union that will live in a different "
                            "header that contains a dictionary from the same header as "
                            "the original dictionary.  This won't compile.  Move the "
                            "inner dictionary to a different Web IDL file to move it "
                            "to a different header.\n%s\n%s"
                            % (t.location, t.inner.location)
                        )
        self.structs = self.getStructs()

    def declare(self):
        return self.structs.declare()

    def define(self):
        return self.structs.define()

    def base(self):
        if self.dictionary.parent:
            return self.makeClassName(self.dictionary.parent)
        return "DictionaryBase"

    def initMethod(self):
        """
        This function outputs the body of the Init() method for the dictionary.

        For the most part, this is some bookkeeping for our atoms so
        we can avoid atomizing strings all the time, then we just spit
        out the getMemberConversion() output for each member,
        separated by newlines.

        """
        body = dedent(
            """
            // Passing a null JSContext is OK only if we're initing from null,
            // Since in that case we will not have to do any property gets
            // Also evaluate isNullOrUndefined in order to avoid false-positive
            // checkers by static analysis tools
            MOZ_ASSERT_IF(!cx, val.isNull() && val.isNullOrUndefined());
            """
        )

        if self.needToInitIds:
            body += fill(
                """
                ${dictName}Atoms* atomsCache = nullptr;
                if (cx) {
                  atomsCache = GetAtomCache<${dictName}Atoms>(cx);
                  if (reinterpret_cast<jsid*>(atomsCache)->isVoid() &&
                      !InitIds(cx, atomsCache)) {
                    return false;
                  }
                }

                """,
                dictName=self.makeClassName(self.dictionary),
            )

        if self.dictionary.parent:
            body += fill(
                """
                // Per spec, we init the parent's members first
                if (!${dictName}::Init(cx, val)) {
                  return false;
                }

                """,
                dictName=self.makeClassName(self.dictionary.parent),
            )
        else:
            body += dedent(
                """
                if (!IsConvertibleToDictionary(val)) {
                  return cx.ThrowErrorMessage<MSG_CONVERSION_ERROR>(sourceDescription, "dictionary");
                }

                """
            )

        memberInits = [self.getMemberConversion(m).define() for m in self.memberInfo]
        if memberInits:
            body += fill(
                """
                bool isNull = val.isNullOrUndefined();
                // We only need these if !isNull, in which case we have |cx|.
                Maybe<JS::Rooted<JSObject *> > object;
                Maybe<JS::Rooted<JS::Value> > temp;
                if (!isNull) {
                  MOZ_ASSERT(cx);
                  object.emplace(cx, &val.toObject());
                  temp.emplace(cx);
                }
                $*{memberInits}
                """,
                memberInits="\n".join(memberInits),
            )

        body += "return true;\n"

        return ClassMethod(
            "Init",
            "bool",
            [
                Argument("BindingCallContext&", "cx"),
                Argument("JS::Handle<JS::Value>", "val"),
                Argument("const char*", "sourceDescription", default='"Value"'),
                Argument("bool", "passedToJSImpl", default="false"),
            ],
            body=body,
        )

    def initWithoutCallContextMethod(self):
        """
        This function outputs the body of an Init() method for the dictionary
        that takes just a JSContext*.  This is needed for non-binding consumers.
        """
        body = dedent(
            """
            // We don't want to use sourceDescription for our context here;
            // that's not really what it's formatted for.
            BindingCallContext cx(cx_, nullptr);
            return Init(cx, val, sourceDescription, passedToJSImpl);
            """
        )
        return ClassMethod(
            "Init",
            "bool",
            [
                Argument("JSContext*", "cx_"),
                Argument("JS::Handle<JS::Value>", "val"),
                Argument("const char*", "sourceDescription", default='"Value"'),
                Argument("bool", "passedToJSImpl", default="false"),
            ],
            body=body,
        )

    def simpleInitMethod(self):
        """
        This function outputs the body of the Init() method for the dictionary,
        for cases when we are just default-initializing it.

        """
        relevantMembers = [
            m
            for m in self.memberInfo
            # We only need to init the things that can have
            # default values.
            if m[0].optional and m[0].defaultValue
        ]

        # We mostly avoid outputting code that uses cx in our native-to-JS
        # conversions, but there is one exception: we may have a
        # dictionary-typed member that _does_ generally support conversion from
        # JS.  If we have such a thing, we can pass it a null JSContext and
        # JS::NullHandleValue to default-initialize it, but since the
        # native-to-JS templates hardcode `cx` as the JSContext value, we're
        # going to need to provide that.
        haveMemberThatNeedsCx = any(
            m[0].type.isDictionary() and m[0].type.unroll().inner.needsConversionFromJS
            for m in relevantMembers
        )
        if haveMemberThatNeedsCx:
            body = dedent(
                """
                JSContext* cx = nullptr;
                """
            )
        else:
            body = ""

        if self.dictionary.parent:
            if self.dictionary.parent.needsConversionFromJS:
                args = "nullptr, JS::NullHandleValue"
            else:
                args = ""
            body += fill(
                """
                // We init the parent's members first
                if (!${dictName}::Init(${args})) {
                  return false;
                }

                """,
                dictName=self.makeClassName(self.dictionary.parent),
                args=args,
            )

        memberInits = [
            self.getMemberConversion(m, isKnownMissing=True).define()
            for m in relevantMembers
        ]
        if memberInits:
            body += fill(
                """
                $*{memberInits}
                """,
                memberInits="\n".join(memberInits),
            )

        body += "return true;\n"

        return ClassMethod(
            "Init",
            "bool",
            [
                Argument("const char*", "sourceDescription", default='"Value"'),
                Argument("bool", "passedToJSImpl", default="false"),
            ],
            body=body,
        )

    def initFromJSONMethod(self):
        return ClassMethod(
            "Init",
            "bool",
            [Argument("const nsAString&", "aJSON")],
            body=dedent(
                """
                AutoJSAPI jsapi;
                JSObject* cleanGlobal = SimpleGlobalObject::Create(SimpleGlobalObject::GlobalType::BindingDetail);
                if (!cleanGlobal) {
                  return false;
                }
                if (!jsapi.Init(cleanGlobal)) {
                  return false;
                }
                JSContext* cx = jsapi.cx();
                JS::Rooted<JS::Value> json(cx);
                bool ok = ParseJSON(cx, aJSON, &json);
                NS_ENSURE_TRUE(ok, false);
                return Init(cx, json);
                """
            ),
        )

    def toJSONMethod(self):
        return ClassMethod(
            "ToJSON",
            "bool",
            [Argument("nsAString&", "aJSON")],
            body=dedent(
                """
                AutoJSAPI jsapi;
                jsapi.Init();
                JSContext *cx = jsapi.cx();
                // It's safe to use UnprivilegedJunkScopeOrWorkerGlobal here
                // because we'll only be creating objects, in ways that have no
                // side-effects, followed by a call to JS::ToJSONMaybeSafely,
                // which likewise guarantees no side-effects for the sorts of
                // things we will pass it.
                JSObject* scope = UnprivilegedJunkScopeOrWorkerGlobal(fallible);
                if (!scope) {
                  JS_ReportOutOfMemory(cx);
                  return false;
                }
                JSAutoRealm ar(cx, scope);
                JS::Rooted<JS::Value> val(cx);
                if (!ToObjectInternal(cx, &val)) {
                  return false;
                }
                JS::Rooted<JSObject*> obj(cx, &val.toObject());
                return StringifyToJSON(cx, obj, aJSON);
            """
            ),
            const=True,
        )

    def toObjectInternalMethod(self):
        body = ""
        if self.needToInitIds:
            body += fill(
                """
                ${dictName}Atoms* atomsCache = GetAtomCache<${dictName}Atoms>(cx);
                if (reinterpret_cast<jsid*>(atomsCache)->isVoid() &&
                    !InitIds(cx, atomsCache)) {
                  return false;
                }

                """,
                dictName=self.makeClassName(self.dictionary),
            )

        if self.dictionary.parent:
            body += fill(
                """
                // Per spec, we define the parent's members first
                if (!${dictName}::ToObjectInternal(cx, rval)) {
                  return false;
                }
                JS::Rooted<JSObject*> obj(cx, &rval.toObject());

                """,
                dictName=self.makeClassName(self.dictionary.parent),
            )
        else:
            body += dedent(
                """
                JS::Rooted<JSObject*> obj(cx, JS_NewPlainObject(cx));
                if (!obj) {
                  return false;
                }
                rval.set(JS::ObjectValue(*obj));

                """
            )

        if self.memberInfo:
            body += "\n".join(
                self.getMemberDefinition(m).define() for m in self.memberInfo
            )
        body += "\nreturn true;\n"

        return ClassMethod(
            "ToObjectInternal",
            "bool",
            [
                Argument("JSContext*", "cx"),
                Argument("JS::MutableHandle<JS::Value>", "rval"),
            ],
            const=True,
            body=body,
        )

    def initIdsMethod(self):
        assert self.needToInitIds
        return initIdsClassMethod(
            [m.identifier.name for m in self.dictionary.members],
            "%sAtoms" % self.makeClassName(self.dictionary),
        )

    def traceDictionaryMethod(self):
        body = ""
        if self.dictionary.parent:
            cls = self.makeClassName(self.dictionary.parent)
            body += "%s::TraceDictionary(trc);\n" % cls

        memberTraces = [
            self.getMemberTrace(m)
            for m in self.dictionary.members
            if typeNeedsRooting(m.type)
        ]

        if memberTraces:
            body += "\n".join(memberTraces)

        return ClassMethod(
            "TraceDictionary",
            "void",
            [
                Argument("JSTracer*", "trc"),
            ],
            body=body,
        )

    @staticmethod
    def dictionaryNeedsCycleCollection(dictionary):
        return any(idlTypeNeedsCycleCollection(m.type) for m in dictionary.members) or (
            dictionary.parent
            and CGDictionary.dictionaryNeedsCycleCollection(dictionary.parent)
        )

    def traverseForCCMethod(self):
        body = ""
        if self.dictionary.parent and self.dictionaryNeedsCycleCollection(
            self.dictionary.parent
        ):
            cls = self.makeClassName(self.dictionary.parent)
            body += "%s::TraverseForCC(aCallback, aFlags);\n" % cls

        for m, _ in self.memberInfo:
            if idlTypeNeedsCycleCollection(m.type):
                memberName = self.makeMemberName(m.identifier.name)
                body += (
                    'ImplCycleCollectionTraverse(aCallback, %s, "%s", aFlags);\n'
                    % (memberName, memberName)
                )

        return ClassMethod(
            "TraverseForCC",
            "void",
            [
                Argument("nsCycleCollectionTraversalCallback&", "aCallback"),
                Argument("uint32_t", "aFlags"),
            ],
            body=body,
            # Inline so we don't pay a codesize hit unless someone actually uses
            # this traverse method.
            inline=True,
            bodyInHeader=True,
        )

    def unlinkForCCMethod(self):
        body = ""
        if self.dictionary.parent and self.dictionaryNeedsCycleCollection(
            self.dictionary.parent
        ):
            cls = self.makeClassName(self.dictionary.parent)
            body += "%s::UnlinkForCC();\n" % cls

        for m, _ in self.memberInfo:
            if idlTypeNeedsCycleCollection(m.type):
                memberName = self.makeMemberName(m.identifier.name)
                body += "ImplCycleCollectionUnlink(%s);\n" % memberName

        return ClassMethod(
            "UnlinkForCC",
            "void",
            [],
            body=body,
            # Inline so we don't pay a codesize hit unless someone actually uses
            # this unlink method.
            inline=True,
            bodyInHeader=True,
        )

    def assignmentOperator(self):
        body = CGList([])
        body.append(CGGeneric("%s::operator=(aOther);\n" % self.base()))

        for m, _ in self.memberInfo:
            memberName = self.makeMemberName(m.identifier.name)
            if m.canHaveMissingValue():
                memberAssign = CGGeneric(
                    fill(
                        """
                    ${name}.Reset();
                    if (aOther.${name}.WasPassed()) {
                      ${name}.Construct(aOther.${name}.Value());
                    }
                    """,
                        name=memberName,
                    )
                )
            else:
                memberAssign = CGGeneric("%s = aOther.%s;\n" % (memberName, memberName))
            body.append(memberAssign)
        body.append(CGGeneric("return *this;\n"))
        return ClassMethod(
            "operator=",
            "%s&" % self.makeClassName(self.dictionary),
            [Argument("const %s&" % self.makeClassName(self.dictionary), "aOther")],
            body=body.define(),
        )

    def equalityOperator(self):
        # For now we only allow equality operators if our members have a string
        # type, a primitive type or an enum type.
        if not all(
            m.type.isString() or m.type.isPrimitive() or m.type.isEnum()
            for m in self.dictionary.members
        ):
            err = (
                "[GenerateEqualityOperator] set on %s, but it"
                % self.dictionary.needsEqualityOperator.identifier.name
            )
            if self.dictionary.needsEqualityOperator != self.dictionary:
                err += "s ancestor %s" % self.dictionary.identifier.name
            err += " contains types other than string, primitive or enum types."
            raise TypeError(err)

        body = CGList([])

        if self.dictionary.parent:
            # If we have a parent dictionary we have to call its equals
            # operator.
            parentTest = CGGeneric(
                fill(
                    """
                    if (!${base}::operator==(aOther)) {
                        return false;
                    }
                    """,
                    base=self.makeClassName(self.dictionary.parent),
                )
            )
            body.append(parentTest)

        for m, _ in self.memberInfo:
            memberName = self.makeMemberName(m.identifier.name)
            memberTest = CGGeneric(
                fill(
                    """
                    if (${memberName} != aOther.${memberName}) {
                        return false;
                    }
                    """,
                    memberName=memberName,
                )
            )
            body.append(memberTest)
        body.append(CGGeneric("return true;\n"))
        return ClassMethod(
            "operator==",
            "bool",
            [Argument("const %s&" % self.makeClassName(self.dictionary), "aOther")],
            const=True,
            body=body.define(),
        )

    def getStructs(self):
        d = self.dictionary
        selfName = self.makeClassName(d)
        members = [
            ClassMember(
                self.makeMemberName(m[0].identifier.name),
                self.getMemberType(m),
                visibility="public",
                body=self.getMemberInitializer(m),
                hasIgnoreInitCheckFlag=True,
            )
            for m in self.memberInfo
        ]
        if d.parent:
            # We always want to init our parent with our non-initializing
            # constructor arg, because either we're about to init ourselves (and
            # hence our parent) or we don't want any init happening.
            baseConstructors = [
                "%s(%s)"
                % (self.makeClassName(d.parent), self.getNonInitializingCtorArg())
            ]
        else:
            baseConstructors = None

        if d.needsConversionFromJS:
            initArgs = "nullptr, JS::NullHandleValue"
        else:
            initArgs = ""
        ctors = [
            ClassConstructor(
                [],
                visibility="public",
                baseConstructors=baseConstructors,
                body=(
                    "// Safe to pass a null context if we pass a null value\n"
                    "Init(%s);\n" % initArgs
                ),
            ),
            ClassConstructor(
                [Argument("const FastDictionaryInitializer&", "")],
                visibility="public",
                baseConstructors=baseConstructors,
                explicit=True,
                bodyInHeader=True,
                body='// Do nothing here; this is used by our "Fast" subclass\n',
            ),
        ]
        methods = []

        if self.needToInitIds:
            methods.append(self.initIdsMethod())

        if d.needsConversionFromJS:
            methods.append(self.initMethod())
            methods.append(self.initWithoutCallContextMethod())
        else:
            methods.append(self.simpleInitMethod())

        canBeRepresentedAsJSON = self.dictionarySafeToJSONify(d)
        if canBeRepresentedAsJSON and d.getExtendedAttribute("GenerateInitFromJSON"):
            methods.append(self.initFromJSONMethod())

        if d.needsConversionToJS:
            methods.append(self.toObjectInternalMethod())

        if canBeRepresentedAsJSON and d.getExtendedAttribute("GenerateToJSON"):
            methods.append(self.toJSONMethod())

        methods.append(self.traceDictionaryMethod())

        try:
            if self.dictionaryNeedsCycleCollection(d):
                methods.append(self.traverseForCCMethod())
                methods.append(self.unlinkForCCMethod())
        except CycleCollectionUnsupported:
            # We have some member that we don't know how to CC.  Don't output
            # our cycle collection overloads, so attempts to CC us will fail to
            # compile instead of misbehaving.
            pass

        ctors.append(
            ClassConstructor(
                [Argument("%s&&" % selfName, "aOther")],
                default=True,
                visibility="public",
                baseConstructors=baseConstructors,
            )
        )

        if CGDictionary.isDictionaryCopyConstructible(d):
            disallowCopyConstruction = False
            # Note: gcc's -Wextra has a warning against not initializng our
            # base explicitly. If we have one. Use our non-initializing base
            # constructor to get around that.
            ctors.append(
                ClassConstructor(
                    [Argument("const %s&" % selfName, "aOther")],
                    bodyInHeader=True,
                    visibility="public",
                    baseConstructors=baseConstructors,
                    explicit=True,
                    body="*this = aOther;\n",
                )
            )
            methods.append(self.assignmentOperator())
        else:
            disallowCopyConstruction = True

        if d.needsEqualityOperator:
            methods.append(self.equalityOperator())
        elif d.parent and d.parent.needsEqualityOperator:
            methods.append(
                ClassMethod(
                    "operator==",
                    "bool",
                    [
                        Argument(
                            "const %s&" % self.makeClassName(self.dictionary), "aOther"
                        )
                    ],
                    visibility="public",
                    delete=True,
                )
            )

        struct = CGClass(
            selfName,
            bases=[ClassBase(self.base())],
            members=members,
            constructors=ctors,
            methods=methods,
            isStruct=True,
            disallowCopyConstruction=disallowCopyConstruction,
        )

        fastDictionaryCtor = ClassConstructor(
            [],
            visibility="public",
            bodyInHeader=True,
            baseConstructors=["%s(%s)" % (selfName, self.getNonInitializingCtorArg())],
            body="// Doesn't matter what int we pass to the parent constructor\n",
        )

        fastStruct = CGClass(
            "Fast" + selfName,
            bases=[ClassBase(selfName)],
            constructors=[fastDictionaryCtor],
            isStruct=True,
        )

        return CGList([struct, CGNamespace("binding_detail", fastStruct)], "\n")

    def deps(self):
        return self.dictionary.getDeps()

    @staticmethod
    def makeDictionaryName(dictionary):
        return dictionary.identifier.name

    def makeClassName(self, dictionary):
        return self.makeDictionaryName(dictionary)

    @staticmethod
    def makeMemberName(name):
        return "m" + name[0].upper() + IDLToCIdentifier(name[1:])

    def getMemberType(self, memberInfo):
        member, conversionInfo = memberInfo
        # We can't handle having a holderType here
        assert conversionInfo.holderType is None

        if member.getExtendedAttribute("BinaryType"):
            return member.getExtendedAttribute("BinaryType")[0]

        declType = conversionInfo.declType
        if conversionInfo.dealWithOptional:
            declType = CGTemplatedType("Optional", declType)
        return declType.define()

    def getMemberConversion(self, memberInfo, isKnownMissing=False):
        """
        A function that outputs the initialization of a single dictionary
        member from the given dictionary value.

        We start with our conversionInfo, which tells us how to
        convert a JS::Value to whatever type this member is.  We
        substiture the template from the conversionInfo with values
        that point to our "temp" JS::Value and our member (which is
        the C++ value we want to produce).  The output is a string of
        code to do the conversion.  We store this string in
        conversionReplacements["convert"].

        Now we have three different ways we might use (or skip) this
        string of code, depending on whether the value is required,
        optional with default value, or optional without default
        value.  We set up a template in the 'conversion' variable for
        exactly how to do this, then substitute into it from the
        conversionReplacements dictionary.
        """
        member, conversionInfo = memberInfo

        # We should only be initializing things with default values if
        # we're always-missing.
        assert not isKnownMissing or (member.optional and member.defaultValue)

        replacements = {
            "declName": self.makeMemberName(member.identifier.name),
            # We need a holder name for external interfaces, but
            # it's scoped down to the conversion so we can just use
            # anything we want.
            "holderName": "holder",
            "passedToJSImpl": "passedToJSImpl",
        }

        if isKnownMissing:
            replacements["val"] = "(JS::NullHandleValue)"
        else:
            replacements["val"] = "temp.ref()"
            replacements["maybeMutableVal"] = "temp.ptr()"

        # We can't handle having a holderType here
        assert conversionInfo.holderType is None
        if conversionInfo.dealWithOptional:
            replacements["declName"] = "(" + replacements["declName"] + ".Value())"
        if member.defaultValue:
            if isKnownMissing:
                replacements["haveValue"] = "false"
            else:
                replacements["haveValue"] = "!isNull && !temp->isUndefined()"

        propId = self.makeIdName(member.identifier.name)
        propGet = "JS_GetPropertyById(cx, *object, atomsCache->%s, temp.ptr())" % propId

        conversionReplacements = {
            "prop": self.makeMemberName(member.identifier.name),
            "convert": string.Template(conversionInfo.template).substitute(
                replacements
            ),
            "propGet": propGet,
        }
        # The conversion code will only run where a default value or a value passed
        # by the author needs to get converted, so we can remember if we have any
        # members present here.
        conversionReplacements["convert"] += "mIsAnyMemberPresent = true;\n"
        if isKnownMissing:
            conversion = ""
        else:
            setTempValue = CGGeneric(
                dedent(
                    """
                if (!${propGet}) {
                  return false;
                }
                """
                )
            )
            conditions = getConditionList(member, "cx", "*object")
            if len(conditions) != 0:
                setTempValue = CGIfElseWrapper(
                    conditions.define(),
                    setTempValue,
                    CGGeneric("temp->setUndefined();\n"),
                )
            setTempValue = CGIfWrapper(setTempValue, "!isNull")
            conversion = setTempValue.define()

        if member.defaultValue:
            if member.type.isUnion() and (
                not member.type.nullable()
                or not isinstance(member.defaultValue, IDLNullValue)
            ):
                # Since this has a default value, it might have been initialized
                # already.  Go ahead and uninit it before we try to init it
                # again.
                memberName = self.makeMemberName(member.identifier.name)
                if member.type.nullable():
                    conversion += fill(
                        """
                        if (!${memberName}.IsNull()) {
                          ${memberName}.Value().Uninit();
                        }
                        """,
                        memberName=memberName,
                    )
                else:
                    conversion += "%s.Uninit();\n" % memberName
            conversion += "${convert}"
        elif not conversionInfo.dealWithOptional:
            # We're required, but have no default value.  Make sure
            # that we throw if we have no value provided.
            conversion += dedent(
                """
                if (!isNull && !temp->isUndefined()) {
                ${convert}
                } else if (cx) {
                  // Don't error out if we have no cx.  In that
                  // situation the caller is default-constructing us and we'll
                  // just assume they know what they're doing.
                  return cx.ThrowErrorMessage<MSG_MISSING_REQUIRED_DICTIONARY_MEMBER>("%s");
                }
                """
                % self.getMemberSourceDescription(member)
            )
            conversionReplacements["convert"] = indent(
                conversionReplacements["convert"]
            ).rstrip()
        else:
            conversion += (
                "if (!isNull && !temp->isUndefined()) {\n"
                "  ${prop}.Construct();\n"
                "${convert}"
                "}\n"
            )
            conversionReplacements["convert"] = indent(
                conversionReplacements["convert"]
            )

        return CGGeneric(string.Template(conversion).substitute(conversionReplacements))

    def getMemberDefinition(self, memberInfo):
        member = memberInfo[0]
        declType = memberInfo[1].declType
        memberLoc = self.makeMemberName(member.identifier.name)
        if not member.canHaveMissingValue():
            memberData = memberLoc
        else:
            # The data is inside the Optional<>
            memberData = "%s.InternalValue()" % memberLoc

        # If you have to change this list (which you shouldn't!), make sure it
        # continues to match the list in test_Object.prototype_props.html
        if member.identifier.name in [
            "constructor",
            "toString",
            "toLocaleString",
            "valueOf",
            "hasOwnProperty",
            "isPrototypeOf",
            "propertyIsEnumerable",
            "__defineGetter__",
            "__defineSetter__",
            "__lookupGetter__",
            "__lookupSetter__",
            "__proto__",
        ]:
            raise TypeError(
                "'%s' member of %s dictionary shadows "
                "a property of Object.prototype, and Xrays to "
                "Object can't handle that.\n"
                "%s"
                % (
                    member.identifier.name,
                    self.dictionary.identifier.name,
                    member.location,
                )
            )

        propDef = (
            "JS_DefinePropertyById(cx, obj, atomsCache->%s, temp, JSPROP_ENUMERATE)"
            % self.makeIdName(member.identifier.name)
        )

        innerTemplate = wrapForType(
            member.type,
            self.descriptorProvider,
            {
                "result": "currentValue",
                "successCode": (
                    "if (!%s) {\n" "  return false;\n" "}\n" "break;\n" % propDef
                ),
                "jsvalRef": "temp",
                "jsvalHandle": "&temp",
                "returnsNewObject": False,
                # 'obj' can just be allowed to be the string "obj", since that
                # will be our dictionary object, which is presumably itself in
                # the right scope.
                "spiderMonkeyInterfacesAreStructs": True,
            },
        )
        conversion = CGGeneric(innerTemplate)
        conversion = CGWrapper(
            conversion,
            pre=(
                "JS::Rooted<JS::Value> temp(cx);\n"
                "%s const & currentValue = %s;\n" % (declType.define(), memberData)
            ),
        )

        # Now make sure that our successCode can actually break out of the
        # conversion.  This incidentally gives us a scope for 'temp' and
        # 'currentValue'.
        conversion = CGWrapper(
            CGIndenter(conversion),
            pre=(
                "do {\n"
                "  // block for our 'break' successCode and scope for 'temp' and 'currentValue'\n"
            ),
            post="} while(false);\n",
        )
        if member.canHaveMissingValue():
            # Only do the conversion if we have a value
            conversion = CGIfWrapper(conversion, "%s.WasPassed()" % memberLoc)
        conditions = getConditionList(member, "cx", "obj")
        if len(conditions) != 0:
            conversion = CGIfWrapper(conversion, conditions.define())
        return conversion

    def getMemberTrace(self, member):
        type = member.type
        assert typeNeedsRooting(type)
        memberLoc = self.makeMemberName(member.identifier.name)
        if not member.canHaveMissingValue():
            memberData = memberLoc
        else:
            # The data is inside the Optional<>
            memberData = "%s.Value()" % memberLoc

        memberName = "%s.%s" % (self.makeClassName(self.dictionary), memberLoc)

        if type.isObject():
            trace = CGGeneric(
                'JS::TraceRoot(trc, %s, "%s");\n' % ("&" + memberData, memberName)
            )
            if type.nullable():
                trace = CGIfWrapper(trace, memberData)
        elif type.isAny():
            trace = CGGeneric(
                'JS::TraceRoot(trc, %s, "%s");\n' % ("&" + memberData, memberName)
            )
        elif (
            type.isSequence()
            or type.isDictionary()
            or type.isSpiderMonkeyInterface()
            or type.isUnion()
            or type.isRecord()
        ):
            if type.nullable():
                memberNullable = memberData
                memberData = "%s.Value()" % memberData
            if type.isSequence():
                trace = CGGeneric("DoTraceSequence(trc, %s);\n" % memberData)
            elif type.isDictionary():
                trace = CGGeneric("%s.TraceDictionary(trc);\n" % memberData)
            elif type.isUnion():
                trace = CGGeneric("%s.TraceUnion(trc);\n" % memberData)
            elif type.isRecord():
                trace = CGGeneric("TraceRecord(trc, %s);\n" % memberData)
            else:
                assert type.isSpiderMonkeyInterface()
                trace = CGGeneric("%s.TraceSelf(trc);\n" % memberData)
            if type.nullable():
                trace = CGIfWrapper(trace, "!%s.IsNull()" % memberNullable)
        else:
            assert False  # unknown type

        if member.canHaveMissingValue():
            trace = CGIfWrapper(trace, "%s.WasPassed()" % memberLoc)

        return trace.define()

    def getMemberInitializer(self, memberInfo):
        """
        Get the right initializer for the member.  Most members don't need one,
        but we need to pre-initialize 'object' that have a default value or are
        required (and hence are not inside Optional), so they're safe to trace
        at all times.  And we can optimize a bit for dictionary-typed members.
        """
        member, _ = memberInfo
        if member.canHaveMissingValue():
            # Allowed missing value means no need to set it up front, since it's
            # inside an Optional and won't get traced until it's actually set
            # up.
            return None
        type = member.type
        if type.isDictionary():
            # When we construct ourselves, we don't want to init our member
            # dictionaries.  Either we're being constructed-but-not-initialized
            # ourselves (and then we don't want to init them) or we're about to
            # init ourselves and then we'll init them anyway.
            return CGDictionary.getNonInitializingCtorArg()
        return initializerForType(type)

    def getMemberSourceDescription(self, member):
        return "'%s' member of %s" % (
            member.identifier.name,
            self.dictionary.identifier.name,
        )

    @staticmethod
    def makeIdName(name):
        return IDLToCIdentifier(name) + "_id"

    @staticmethod
    def getNonInitializingCtorArg():
        return "FastDictionaryInitializer()"

    @staticmethod
    def isDictionaryCopyConstructible(dictionary):
        if dictionary.parent and not CGDictionary.isDictionaryCopyConstructible(
            dictionary.parent
        ):
            return False
        return all(isTypeCopyConstructible(m.type) for m in dictionary.members)

    @staticmethod
    def typeSafeToJSONify(type):
        """
        Determine whether the given type is safe to convert to JSON.  The
        restriction is that this needs to be safe while in a global controlled
        by an adversary, and "safe" means no side-effects when the JS
        representation of this type is converted to JSON.  That means that we
        have to be pretty restrictive about what things we can allow.  For
        example, "object" is out, because it may have accessor properties on it.
        """
        if type.nullable():
            # Converting null to JSON is always OK.
            return CGDictionary.typeSafeToJSONify(type.inner)

        if type.isSequence():
            # Sequences are arrays we create ourselves, with no holes.  They
            # should be safe if their contents are safe, as long as we suppress
            # invocation of .toJSON on objects.
            return CGDictionary.typeSafeToJSONify(type.inner)

        if type.isUnion():
            # OK if everything in it is ok.
            return all(CGDictionary.typeSafeToJSONify(t) for t in type.flatMemberTypes)

        if type.isDictionary():
            # OK if the dictionary is OK
            return CGDictionary.dictionarySafeToJSONify(type.inner)

        if type.isUndefined() or type.isString() or type.isEnum():
            # Strings are always OK.
            return True

        if type.isPrimitive():
            # Primitives (numbers and booleans) are ok, as long as
            # they're not unrestricted float/double.
            return not type.isFloat() or not type.isUnrestricted()

        if type.isRecord():
            # Records are okay, as long as the value type is.
            # Per spec, only strings are allowed as keys.
            return CGDictionary.typeSafeToJSONify(type.inner)

        return False

    @staticmethod
    def dictionarySafeToJSONify(dictionary):
        # The dictionary itself is OK, so we're good if all our types are.
        return all(CGDictionary.typeSafeToJSONify(m.type) for m in dictionary.members)


def RegisterNonWindowBindings(descriptors):
    conditions = []
    for desc in descriptors:
        bindingNS = toBindingNamespace(desc.name)
        condition = "!%s::CreateAndDefineOnGlobal(aCx)" % bindingNS
        if desc.isExposedConditionally():
            condition = "%s::ConstructorEnabled(aCx, aObj) && " % bindingNS + condition
        conditions.append(condition)
    lines = [
        CGIfWrapper(CGGeneric("return false;\n"), condition) for condition in conditions
    ]
    lines.append(CGGeneric("return true;\n"))
    return CGList(lines, "\n").define()


class CGRegisterWorkerBindings(CGAbstractMethod):
    def __init__(self, config):
        CGAbstractMethod.__init__(
            self,
            None,
            "RegisterWorkerBindings",
            "bool",
            [Argument("JSContext*", "aCx"), Argument("JS::Handle<JSObject*>", "aObj")],
        )
        self.config = config

    def definition_body(self):
        return RegisterNonWindowBindings(
            self.config.getDescriptors(
                hasInterfaceObject=True, isExposedInAnyWorker=True, register=True
            )
        )


class CGRegisterWorkerDebuggerBindings(CGAbstractMethod):
    def __init__(self, config):
        CGAbstractMethod.__init__(
            self,
            None,
            "RegisterWorkerDebuggerBindings",
            "bool",
            [Argument("JSContext*", "aCx"), Argument("JS::Handle<JSObject*>", "aObj")],
        )
        self.config = config

    def definition_body(self):
        return RegisterNonWindowBindings(
            self.config.getDescriptors(
                hasInterfaceObject=True, isExposedInWorkerDebugger=True, register=True
            )
        )


class CGRegisterWorkletBindings(CGAbstractMethod):
    def __init__(self, config):
        CGAbstractMethod.__init__(
            self,
            None,
            "RegisterWorkletBindings",
            "bool",
            [Argument("JSContext*", "aCx"), Argument("JS::Handle<JSObject*>", "aObj")],
        )
        self.config = config

    def definition_body(self):
        return RegisterNonWindowBindings(
            self.config.getDescriptors(
                hasInterfaceObject=True, isExposedInAnyWorklet=True, register=True
            )
        )


class CGRegisterShadowRealmBindings(CGAbstractMethod):
    def __init__(self, config):
        CGAbstractMethod.__init__(
            self,
            None,
            "RegisterShadowRealmBindings",
            "bool",
            [Argument("JSContext*", "aCx"), Argument("JS::Handle<JSObject*>", "aObj")],
        )
        self.config = config

    def definition_body(self):
        return RegisterNonWindowBindings(
            self.config.getDescriptors(
                hasInterfaceObject=True, isExposedInShadowRealms=True, register=True
            )
        )


def BindingNamesOffsetEnum(name):
    return CppKeywords.checkMethodName(name.replace(" ", "_"))


class CGGlobalNames(CGGeneric):
    def __init__(self, names):
        """
        names is expected to be a list of tuples of the name and the descriptor it refers to.
        """

        strings = []
        entries = []
        for name, desc in names:
            # Generate the entry declaration
            # XXX(nika): mCreate & mEnabled require relocations. If we want to
            # reduce those, we could move them into separate tables.
            nativeEntry = fill(
                """
                {
                  /* mNameOffset */ BindingNamesOffset::${nameOffset},
                  /* mNameLength */ ${nameLength},
                  /* mConstructorId */ constructors::id::${realname},
                  /* mCreate */ ${realname}_Binding::CreateInterfaceObjects,
                  /* mEnabled */ ${enabled}
                }
                """,
                nameOffset=BindingNamesOffsetEnum(name),
                nameLength=len(name),
                name=name,
                realname=desc.name,
                enabled=(
                    "%s_Binding::ConstructorEnabled" % desc.name
                    if desc.isExposedConditionally()
                    else "nullptr"
                ),
            )

            entries.append((name.encode(), nativeEntry))

        # Unfortunately, when running tests, we may have no entries.
        # PerfectHash will assert if we give it an empty set of entries, so we
        # just generate a dummy value.
        if len(entries) == 0:
            CGGeneric.__init__(
                self,
                define=dedent(
                    """
                static_assert(false, "No WebIDL global name entries!");
                """
                ),
            )
            return

        # Build the perfect hash function.
        phf = PerfectHash(entries, GLOBAL_NAMES_PHF_SIZE)

        # Generate code for the PHF
        phfCodegen = phf.codegen(
            "WebIDLGlobalNameHash::sEntries", "WebIDLNameTableEntry"
        )
        entries = phfCodegen.gen_entries(lambda e: e[1])
        getter = phfCodegen.gen_jslinearstr_getter(
            name="WebIDLGlobalNameHash::GetEntry",
            return_type="const WebIDLNameTableEntry*",
            return_entry=dedent(
                """
                if (JS_LinearStringEqualsAscii(aKey, BindingName(entry.mNameOffset), entry.mNameLength)) {
                  return &entry;
                }
                return nullptr;
                """
            ),
        )

        define = fill(
            """
            const uint32_t WebIDLGlobalNameHash::sCount = ${count};

            $*{entries}

            $*{getter}
            """,
            count=len(phf.entries),
            strings="\n".join(strings) + ";\n",
            entries=entries,
            getter=getter,
        )
        CGGeneric.__init__(self, define=define)


def dependencySortObjects(objects, dependencyGetter, nameGetter):
    """
    Sort IDL objects with dependencies on each other such that if A
    depends on B then B will come before A.  This is needed for
    declaring C++ classes in the right order, for example.  Objects
    that have no dependencies are just sorted by name.

    objects should be something that can produce a set of objects
    (e.g. a set, iterator, list, etc).

    dependencyGetter is something that, given an object, should return
    the set of objects it depends on.
    """
    # XXXbz this will fail if we have two webidl files F1 and F2 such that F1
    # declares an object which depends on an object in F2, and F2 declares an
    # object (possibly a different one!) that depends on an object in F1.  The
    # good news is that I expect this to never happen.
    sortedObjects = []
    objects = set(objects)
    while len(objects) != 0:
        # Find the dictionaries that don't depend on anything else
        # anymore and move them over.
        toMove = [o for o in objects if len(dependencyGetter(o) & objects) == 0]
        if len(toMove) == 0:
            raise TypeError(
                "Loop in dependency graph\n" + "\n".join(o.location for o in objects)
            )
        objects = objects - set(toMove)
        sortedObjects.extend(sorted(toMove, key=nameGetter))
    return sortedObjects


class ForwardDeclarationBuilder:
    """
    Create a canonical representation of a set of namespaced forward
    declarations.
    """

    def __init__(self):
        """
        The set of declarations is represented as a tree of nested namespaces.
        Each tree node has a set of declarations |decls| and a dict |children|.
        Each declaration is a pair consisting of the class name and a boolean
        that is true iff the class is really a struct. |children| maps the
        names of inner namespaces to the declarations in that namespace.
        """
        self.decls = set()
        self.children = {}

    def _ensureNonTemplateType(self, type):
        if "<" in type:
            # This is a templated type.  We don't really know how to
            # forward-declare those, and trying to do it naively is not going to
            # go well (e.g. we may have :: characters inside the type we're
            # templated on!).  Just bail out.
            raise TypeError(
                "Attempt to use ForwardDeclarationBuilder on "
                "templated type %s.  We don't know how to do that "
                "yet." % type
            )

    def _listAdd(self, namespaces, name, isStruct=False):
        """
        Add a forward declaration, where |namespaces| is a list of namespaces.
        |name| should not contain any other namespaces.
        """
        if namespaces:
            child = self.children.setdefault(namespaces[0], ForwardDeclarationBuilder())
            child._listAdd(namespaces[1:], name, isStruct)
        else:
            assert "::" not in name
            self.decls.add((name, isStruct))

    def addInMozillaDom(self, name, isStruct=False):
        """
        Add a forward declaration to the mozilla::dom:: namespace. |name| should not
        contain any other namespaces.
        """
        self._ensureNonTemplateType(name)
        self._listAdd(["mozilla", "dom"], name, isStruct)

    def add(self, nativeType, isStruct=False):
        """
        Add a forward declaration, where |nativeType| is a string containing
        the type and its namespaces, in the usual C++ way.
        """
        self._ensureNonTemplateType(nativeType)
        components = nativeType.split("::")
        self._listAdd(components[:-1], components[-1], isStruct)

    def _build(self, atTopLevel):
        """
        Return a codegenerator for the forward declarations.
        """
        decls = []
        if self.decls:
            decls.append(
                CGList(
                    [
                        CGClassForwardDeclare(cname, isStruct)
                        for cname, isStruct in sorted(self.decls)
                    ]
                )
            )
        for namespace, child in sorted(self.children.items()):
            decls.append(CGNamespace(namespace, child._build(atTopLevel=False)))

        cg = CGList(decls, "\n")
        if not atTopLevel and len(decls) + len(self.decls) > 1:
            cg = CGWrapper(cg, pre="\n", post="\n")
        return cg

    def build(self):
        return self._build(atTopLevel=True)

    def forwardDeclareForType(self, t, config):
        t = t.unroll()
        if t.isGeckoInterface():
            name = t.inner.identifier.name
            try:
                desc = config.getDescriptor(name)
                self.add(desc.nativeType)
            except NoSuchDescriptorError:
                pass

        # Note: SpiderMonkey interfaces are typedefs, so can't be
        # forward-declared
        elif t.isPromise():
            self.addInMozillaDom("Promise")
        elif t.isCallback():
            self.addInMozillaDom(t.callback.identifier.name)
        elif t.isDictionary():
            self.addInMozillaDom(t.inner.identifier.name, isStruct=True)
        elif t.isCallbackInterface():
            self.addInMozillaDom(t.inner.identifier.name)
        elif t.isUnion():
            # Forward declare both the owning and non-owning version,
            # since we don't know which one we might want
            self.addInMozillaDom(CGUnionStruct.unionTypeName(t, False))
            self.addInMozillaDom(CGUnionStruct.unionTypeName(t, True))
        elif t.isRecord():
            self.forwardDeclareForType(t.inner, config)
        # Don't need to do anything for void, primitive, string, any or object.
        # There may be some other cases we are missing.


class CGForwardDeclarations(CGWrapper):
    """
    Code generate the forward declarations for a header file.
    additionalDeclarations is a list of tuples containing a classname and a
    boolean. If the boolean is true we will declare a struct, otherwise we'll
    declare a class.
    """

    def __init__(
        self,
        config,
        descriptors,
        callbacks,
        dictionaries,
        callbackInterfaces,
        additionalDeclarations=[],
    ):
        builder = ForwardDeclarationBuilder()

        # Needed for at least Wrap.
        for d in descriptors:
            # If this is a generated iterator interface, we only create these
            # in the generated bindings, and don't need to forward declare.
            if (
                d.interface.isIteratorInterface()
                or d.interface.isAsyncIteratorInterface()
            ):
                continue
            builder.add(d.nativeType)
            if d.interface.isSerializable():
                builder.add("nsIGlobalObject")
            # If we're an interface and we have a maplike/setlike declaration,
            # we'll have helper functions exposed to the native side of our
            # bindings, which will need to show up in the header. If either of
            # our key/value types are interfaces, they'll be passed as
            # arguments to helper functions, and they'll need to be forward
            # declared in the header.
            if d.interface.maplikeOrSetlikeOrIterable:
                if d.interface.maplikeOrSetlikeOrIterable.hasKeyType():
                    builder.forwardDeclareForType(
                        d.interface.maplikeOrSetlikeOrIterable.keyType, config
                    )
                if d.interface.maplikeOrSetlikeOrIterable.hasValueType():
                    builder.forwardDeclareForType(
                        d.interface.maplikeOrSetlikeOrIterable.valueType, config
                    )

            for m in d.interface.members:
                if m.isAttr() and m.type.isObservableArray():
                    builder.forwardDeclareForType(m.type, config)

        # We just about always need NativePropertyHooks
        builder.addInMozillaDom("NativePropertyHooks", isStruct=True)
        builder.addInMozillaDom("ProtoAndIfaceCache")

        for callback in callbacks:
            builder.addInMozillaDom(callback.identifier.name)
            for t in getTypesFromCallback(callback):
                builder.forwardDeclareForType(t, config)

        for d in callbackInterfaces:
            builder.add(d.nativeType)
            builder.add(d.nativeType + "Atoms", isStruct=True)
            for t in getTypesFromDescriptor(d):
                builder.forwardDeclareForType(t, config)
            if d.hasCEReactions():
                builder.addInMozillaDom("DocGroup")

        for d in dictionaries:
            if len(d.members) > 0:
                builder.addInMozillaDom(d.identifier.name + "Atoms", isStruct=True)
            for t in getTypesFromDictionary(d):
                builder.forwardDeclareForType(t, config)

        for className, isStruct in additionalDeclarations:
            builder.add(className, isStruct=isStruct)

        CGWrapper.__init__(self, builder.build())


def dependencySortDictionariesAndUnionsAndCallbacks(types):
    def getDependenciesFromType(type):
        if type.isDictionary():
            return set([type.unroll().inner])
        if type.isSequence():
            return getDependenciesFromType(type.unroll())
        if type.isUnion():
            return set([type.unroll()])
        if type.isRecord():
            return set([type.unroll().inner])
        if type.isCallback():
            return set([type.unroll()])
        return set()

    def getDependencies(unionTypeOrDictionaryOrCallback):
        if isinstance(unionTypeOrDictionaryOrCallback, IDLDictionary):
            deps = set()
            if unionTypeOrDictionaryOrCallback.parent:
                deps.add(unionTypeOrDictionaryOrCallback.parent)
            for member in unionTypeOrDictionaryOrCallback.members:
                deps |= getDependenciesFromType(member.type)
            return deps

        if (
            unionTypeOrDictionaryOrCallback.isType()
            and unionTypeOrDictionaryOrCallback.isUnion()
        ):
            deps = set()
            for member in unionTypeOrDictionaryOrCallback.flatMemberTypes:
                deps |= getDependenciesFromType(member)
            return deps

        assert unionTypeOrDictionaryOrCallback.isCallback()
        return set()

    def getName(unionTypeOrDictionaryOrCallback):
        if isinstance(unionTypeOrDictionaryOrCallback, IDLDictionary):
            return unionTypeOrDictionaryOrCallback.identifier.name

        if (
            unionTypeOrDictionaryOrCallback.isType()
            and unionTypeOrDictionaryOrCallback.isUnion()
        ):
            return unionTypeOrDictionaryOrCallback.name

        assert unionTypeOrDictionaryOrCallback.isCallback()
        return unionTypeOrDictionaryOrCallback.identifier.name

    return dependencySortObjects(types, getDependencies, getName)


class CGBindingRoot(CGThing):
    """
    Root codegen class for binding generation. Instantiate the class, and call
    declare or define to generate header or cpp code (respectively).
    """

    def __init__(self, config, prefix, webIDLFile):
        bindingHeaders = dict.fromkeys(
            ("mozilla/dom/NonRefcountedDOMObject.h", "MainThreadUtils.h"), True
        )
        bindingDeclareHeaders = dict.fromkeys(
            (
                "mozilla/dom/BindingDeclarations.h",
                "mozilla/dom/Nullable.h",
            ),
            True,
        )

        descriptors = config.getDescriptors(
            webIDLFile=webIDLFile, hasInterfaceOrInterfacePrototypeObject=True
        )
        descriptors.extend(
            config.getDescriptors(
                webIDLFile=webIDLFile, hasOrdinaryObjectPrototype=True
            )
        )

        unionTypes = UnionsForFile(config, webIDLFile)

        (
            unionHeaders,
            unionImplheaders,
            unionDeclarations,
            traverseMethods,
            unlinkMethods,
            unionStructs,
        ) = UnionTypes(unionTypes, config)

        bindingDeclareHeaders.update(dict.fromkeys(unionHeaders, True))
        bindingHeaders.update(dict.fromkeys(unionImplheaders, True))
        bindingDeclareHeaders["mozilla/dom/UnionMember.h"] = len(unionStructs) > 0
        bindingDeclareHeaders["mozilla/dom/FakeString.h"] = len(unionStructs) > 0
        # BindingUtils.h is only needed for SetToObject.
        # If it stops being inlined or stops calling CallerSubsumes
        # both this bit and the bit in UnionTypes can be removed.
        bindingDeclareHeaders["mozilla/dom/BindingUtils.h"] = any(
            d.isObject() for t in unionTypes for d in t.flatMemberTypes
        )
        bindingDeclareHeaders["mozilla/dom/JSSlots.h"] = any(
            d.interface.reflectedHTMLAttributesReturningFrozenArray for d in descriptors
        )
        bindingHeaders["mozilla/dom/IterableIterator.h"] = any(
            (
                d.interface.isIteratorInterface()
                and d.interface.maplikeOrSetlikeOrIterable.isPairIterator()
            )
            or d.interface.isAsyncIteratorInterface()
            or d.interface.isIterable()
            or d.interface.isAsyncIterable()
            for d in descriptors
        )

        def memberNeedsSubjectPrincipal(d, m):
            if m.isAttr():
                return (
                    "needsSubjectPrincipal" in d.getExtendedAttributes(m, getter=True)
                ) or (
                    not m.readonly
                    and "needsSubjectPrincipal"
                    in d.getExtendedAttributes(m, setter=True)
                )
            return m.isMethod() and "needsSubjectPrincipal" in d.getExtendedAttributes(
                m
            )

        if any(
            memberNeedsSubjectPrincipal(d, m)
            for d in descriptors
            for m in d.interface.members
        ):
            bindingHeaders["mozilla/BasePrincipal.h"] = True
            bindingHeaders["nsJSPrincipals.h"] = True

        # The conditions for which we generate profiler labels are fairly
        # complicated. The check below is a little imprecise to make it simple.
        # It includes the profiler header in all cases where it is necessary and
        # generates only a few false positives.
        bindingHeaders["mozilla/ProfilerLabels.h"] = any(
            # constructor profiler label
            d.interface.legacyFactoryFunctions
            or (d.interface.hasInterfaceObject() and d.interface.ctor())
            or any(
                # getter/setter profiler labels
                m.isAttr()
                # method profiler label
                or m.isMethod()
                for m in d.interface.members
            )
            for d in descriptors
        )

        def descriptorHasCrossOriginProperties(desc):
            def hasCrossOriginProperty(m):
                props = memberProperties(m, desc)
                return (
                    props.isCrossOriginMethod
                    or props.isCrossOriginGetter
                    or props.isCrossOriginSetter
                )

            return any(hasCrossOriginProperty(m) for m in desc.interface.members)

        def descriptorHasObservableArrayTypes(desc):
            def hasObservableArrayTypes(m):
                return m.isAttr() and m.type.isObservableArray()

            return any(hasObservableArrayTypes(m) for m in desc.interface.members)

        bindingDeclareHeaders["mozilla/dom/RemoteObjectProxy.h"] = any(
            descriptorHasCrossOriginProperties(d) for d in descriptors
        )
        bindingDeclareHeaders["jsapi.h"] = any(
            descriptorHasCrossOriginProperties(d)
            or descriptorHasObservableArrayTypes(d)
            for d in descriptors
        )
        bindingDeclareHeaders["js/TypeDecls.h"] = not bindingDeclareHeaders["jsapi.h"]
        bindingDeclareHeaders["js/RootingAPI.h"] = not bindingDeclareHeaders["jsapi.h"]

        # JS::IsCallable
        bindingDeclareHeaders["js/CallAndConstruct.h"] = True

        def descriptorHasIteratorAlias(desc):
            def hasIteratorAlias(m):
                return m.isMethod() and (
                    ("@@iterator" in m.aliases) or ("@@asyncIterator" in m.aliases)
                )

            return any(hasIteratorAlias(m) for m in desc.interface.members)

        bindingHeaders["js/Symbol.h"] = any(
            descriptorHasIteratorAlias(d) for d in descriptors
        )

        bindingHeaders["js/shadow/Object.h"] = any(
            d.interface.hasMembersInSlots() for d in descriptors
        )

        # The symbols supplied by this header are used so ubiquitously it's not
        # worth the effort delineating the exact dependency, if it can't be done
        # *at* the places where their definitions are required.
        bindingHeaders["js/experimental/JitInfo.h"] = True

        # JS::GetClass, JS::GetCompartment, JS::GetReservedSlot, and
        # JS::SetReservedSlot are also used too many places to restate
        # dependency logic.
        bindingHeaders["js/Object.h"] = True

        # JS::IsCallable, JS::Call, JS::Construct
        bindingHeaders["js/CallAndConstruct.h"] = True

        # JS_IsExceptionPending
        bindingHeaders["js/Exception.h"] = True

        # JS::Map{Clear, Delete, Has, Get, Set}
        bindingHeaders["js/MapAndSet.h"] = True

        # JS_DefineElement, JS_DefineProperty, JS_DefinePropertyById,
        # JS_DefineUCProperty, JS_ForwardGetPropertyTo, JS_GetProperty,
        # JS_GetPropertyById, JS_HasPropertyById, JS_SetProperty,
        # JS_SetPropertyById
        bindingHeaders["js/PropertyAndElement.h"] = True

        # JS_GetOwnPropertyDescriptorById
        bindingHeaders["js/PropertyDescriptor.h"] = True

        def descriptorDeprecated(desc):
            iface = desc.interface
            return any(
                m.getExtendedAttribute("Deprecated") for m in iface.members + [iface]
            )

        bindingHeaders["mozilla/dom/Document.h"] = any(
            descriptorDeprecated(d) for d in descriptors
        )

        bindingHeaders["mozilla/dom/DOMJSProxyHandler.h"] = any(
            d.concrete and d.proxy for d in descriptors
        )

        bindingHeaders["mozilla/dom/ProxyHandlerUtils.h"] = any(
            d.concrete and d.proxy for d in descriptors
        )

        bindingHeaders["js/String.h"] = any(
            d.needsMissingPropUseCounters for d in descriptors
        )

        hasCrossOriginObjects = any(
            d.concrete and d.isMaybeCrossOriginObject() for d in descriptors
        )
        bindingHeaders["mozilla/dom/MaybeCrossOriginObject.h"] = hasCrossOriginObjects
        bindingHeaders["AccessCheck.h"] = hasCrossOriginObjects
        hasCEReactions = any(d.hasCEReactions() for d in descriptors)
        bindingHeaders["mozilla/dom/CustomElementRegistry.h"] = hasCEReactions
        bindingHeaders["mozilla/dom/DocGroup.h"] = hasCEReactions

        def descriptorHasChromeOnly(desc):
            ctor = desc.interface.ctor()

            return (
                any(
                    isChromeOnly(a) or needsCallerType(a)
                    for a in desc.interface.members
                )
                or desc.interface.getExtendedAttribute("ChromeOnly") is not None
                or
                # JS-implemented interfaces with an interface object get a
                # chromeonly _create method.  And interfaces with an
                # interface object might have a ChromeOnly constructor.
                (
                    desc.interface.hasInterfaceObject()
                    and (
                        desc.interface.isJSImplemented()
                        or (ctor and isChromeOnly(ctor))
                    )
                )
            )

        # XXXkhuey ugly hack but this is going away soon.
        bindingHeaders["xpcprivate.h"] = webIDLFile.endswith("EventTarget.webidl")

        hasThreadChecks = any(d.hasThreadChecks() for d in descriptors)
        bindingHeaders["nsThreadUtils.h"] = hasThreadChecks

        dictionaries = config.getDictionaries(webIDLFile)

        def dictionaryHasChromeOnly(dictionary):
            while dictionary:
                if any(isChromeOnly(m) for m in dictionary.members):
                    return True
                dictionary = dictionary.parent
            return False

        def needsNonSystemPrincipal(member):
            return (
                member.getExtendedAttribute("NeedsSubjectPrincipal") == ["NonSystem"]
                or member.getExtendedAttribute("SetterNeedsSubjectPrincipal")
                == ["NonSystem"]
                or member.getExtendedAttribute("GetterNeedsSubjectPrincipal")
                == ["NonSystem"]
            )

        def descriptorNeedsNonSystemPrincipal(d):
            return any(needsNonSystemPrincipal(m) for m in d.interface.members)

        def descriptorHasPrefDisabler(desc):
            iface = desc.interface
            return any(
                PropertyDefiner.getControllingCondition(m, desc).hasDisablers()
                for m in iface.members
                if (m.isMethod() or m.isAttr() or m.isConst())
            )

        def addPrefHeaderForObject(bindingHeaders, obj):
            """
            obj might be a dictionary member or an interface.
            """
            if obj is not None:
                pref = PropertyDefiner.getStringAttr(obj, "Pref")
                if pref:
                    bindingHeaders[prefHeader(pref)] = True

        def addPrefHeadersForDictionary(bindingHeaders, dictionary):
            while dictionary:
                for m in dictionary.members:
                    addPrefHeaderForObject(bindingHeaders, m)
                dictionary = dictionary.parent

        for d in dictionaries:
            addPrefHeadersForDictionary(bindingHeaders, d)
        for d in descriptors:
            interface = d.interface
            addPrefHeaderForObject(bindingHeaders, interface)
            addPrefHeaderForObject(bindingHeaders, interface.ctor())

        bindingHeaders["mozilla/dom/WebIDLPrefs.h"] = any(
            descriptorHasPrefDisabler(d) for d in descriptors
        )
        bindingHeaders["nsContentUtils.h"] = (
            any(descriptorHasChromeOnly(d) for d in descriptors)
            or any(descriptorNeedsNonSystemPrincipal(d) for d in descriptors)
            or any(dictionaryHasChromeOnly(d) for d in dictionaries)
        )
        hasNonEmptyDictionaries = any(len(dict.members) > 0 for dict in dictionaries)
        callbacks = config.getCallbacks(webIDLFile)
        callbackDescriptors = config.getDescriptors(
            webIDLFile=webIDLFile, isCallback=True
        )
        jsImplemented = config.getDescriptors(
            webIDLFile=webIDLFile, isJSImplemented=True
        )
        bindingDeclareHeaders["nsWeakReference.h"] = jsImplemented
        bindingDeclareHeaders["mozilla/dom/PrototypeList.h"] = descriptors
        bindingHeaders["nsIGlobalObject.h"] = jsImplemented
        bindingHeaders["AtomList.h"] = (
            hasNonEmptyDictionaries or jsImplemented or callbackDescriptors
        )

        if callbackDescriptors:
            bindingDeclareHeaders["mozilla/ErrorResult.h"] = True

        def descriptorClearsPropsInSlots(descriptor):
            if not descriptor.wrapperCache:
                return False
            return any(
                m.isAttr() and m.getExtendedAttribute("StoreInSlot")
                for m in descriptor.interface.members
            )

        bindingHeaders["nsJSUtils.h"] = any(
            descriptorClearsPropsInSlots(d) for d in descriptors
        )

        # Make sure we can sanely use binding_detail in generated code.
        cgthings = [
            CGGeneric(
                dedent(
                    """
            namespace binding_detail {}; // Just to make sure it's known as a namespace
            using namespace mozilla::dom::binding_detail;
            """
                )
            )
        ]

        # Do codegen for all the enums
        enums = config.getEnums(webIDLFile)
        cgthings.extend(CGEnum(e) for e in enums)
        maxEnumValues = CGList([CGMaxContiguousEnumValue(e) for e in enums], "\n")

        bindingDeclareHeaders["mozilla/Span.h"] = enums
        bindingDeclareHeaders["mozilla/ArrayUtils.h"] = enums
        bindingDeclareHeaders["mozilla/EnumTypeTraits.h"] = enums

        hasCode = descriptors or callbackDescriptors or dictionaries or callbacks
        bindingHeaders["mozilla/dom/BindingUtils.h"] = hasCode
        bindingHeaders["mozilla/OwningNonNull.h"] = hasCode
        bindingHeaders["<type_traits>"] = hasCode
        bindingHeaders["mozilla/dom/BindingDeclarations.h"] = not hasCode and enums

        bindingHeaders["WrapperFactory.h"] = descriptors
        bindingHeaders["mozilla/dom/DOMJSClass.h"] = descriptors
        bindingHeaders["mozilla/dom/ScriptSettings.h"] = dictionaries  # AutoJSAPI
        # Ensure we see our enums in the generated .cpp file, for the ToJSValue
        # method body.  Also ensure that we see jsapi.h.
        if enums:
            bindingHeaders[CGHeaders.getDeclarationFilename(enums[0])] = True
            bindingHeaders["jsapi.h"] = True

        # For things that have [UseCounter] or [InstrumentedProps] or [Trial]
        for d in descriptors:
            if d.concrete:
                if d.instrumentedProps:
                    bindingHeaders["mozilla/UseCounter.h"] = True
                if d.needsMissingPropUseCounters:
                    bindingHeaders[prefHeader(MISSING_PROP_PREF)] = True
            if d.interface.isSerializable():
                bindingHeaders["mozilla/dom/StructuredCloneTags.h"] = True
            if d.wantsXrays:
                bindingHeaders["mozilla/Atomics.h"] = True
                bindingHeaders["mozilla/dom/XrayExpandoClass.h"] = True
                if d.wantsXrayExpandoClass:
                    bindingHeaders["XrayWrapper.h"] = True
            for m in d.interface.members:
                if m.getExtendedAttribute("UseCounter"):
                    bindingHeaders["mozilla/UseCounter.h"] = True
                if m.getExtendedAttribute("Trial"):
                    bindingHeaders["mozilla/OriginTrials.h"] = True

        bindingHeaders["mozilla/dom/SimpleGlobalObject.h"] = any(
            CGDictionary.dictionarySafeToJSONify(d) for d in dictionaries
        )

        for ancestor in (findAncestorWithInstrumentedProps(d) for d in descriptors):
            if not ancestor:
                continue
            bindingHeaders[CGHeaders.getDeclarationFilename(ancestor)] = True

        for d in descriptors:
            ancestor = d.interface.parent
            while ancestor:
                if ancestor.reflectedHTMLAttributesReturningFrozenArray:
                    bindingHeaders[CGHeaders.getDeclarationFilename(ancestor)] = True
                    break
                ancestor = ancestor.parent

        cgthings.extend(traverseMethods)
        cgthings.extend(unlinkMethods)

        # Do codegen for all the dictionaries.  We have to be a bit careful
        # here, because we have to generate these in order from least derived
        # to most derived so that class inheritance works out.  We also have to
        # generate members before the dictionary that contains them.

        for t in dependencySortDictionariesAndUnionsAndCallbacks(
            dictionaries + unionStructs + callbacks
        ):
            if t.isDictionary():
                cgthings.append(CGDictionary(t, config))
            elif t.isUnion():
                cgthings.append(CGUnionStruct(t, config))
                cgthings.append(CGUnionStruct(t, config, True))
            else:
                assert t.isCallback()
                cgthings.append(CGCallbackFunction(t, config))
                cgthings.append(CGNamespace("binding_detail", CGFastCallback(t)))

        # Do codegen for all the descriptors
        cgthings.extend(
            [CGDescriptor(x, config.attributeTemplates) for x in descriptors]
        )

        # Do codegen for all the callback interfaces.
        cgthings.extend([CGCallbackInterface(x) for x in callbackDescriptors])

        cgthings.extend(
            [
                CGNamespace("binding_detail", CGFastCallback(x.interface))
                for x in callbackDescriptors
            ]
        )

        # Do codegen for JS implemented classes
        def getParentDescriptor(desc):
            if not desc.interface.parent:
                return set()
            return {desc.getDescriptor(desc.interface.parent.identifier.name)}

        for x in dependencySortObjects(
            jsImplemented, getParentDescriptor, lambda d: d.interface.identifier.name
        ):
            cgthings.append(
                CGCallbackInterface(x, spiderMonkeyInterfacesAreStructs=True)
            )
            cgthings.append(CGJSImplClass(x))

        # And make sure we have the right number of newlines at the end
        curr = CGWrapper(CGList(cgthings, "\n\n"), post="\n\n")

        # Wrap all of that in our namespaces.

        if len(maxEnumValues) > 0:
            curr = CGNamespace("dom", CGWrapper(curr, pre="\n"))
            curr = CGWrapper(CGList([curr, maxEnumValues], "\n\n"), post="\n\n")
            curr = CGNamespace("mozilla", CGWrapper(curr, pre="\n"))
        else:
            curr = CGNamespace.build(["mozilla", "dom"], CGWrapper(curr, pre="\n"))

        curr = CGList(
            [
                CGForwardDeclarations(
                    config,
                    descriptors,
                    callbacks,
                    dictionaries,
                    callbackDescriptors + jsImplemented,
                    additionalDeclarations=unionDeclarations,
                ),
                curr,
            ],
            "\n",
        )

        # Add header includes.
        bindingHeaders = [
            header for header, include in bindingHeaders.items() if include
        ]
        bindingDeclareHeaders = [
            header for header, include in bindingDeclareHeaders.items() if include
        ]

        curr = CGHeaders(
            descriptors,
            dictionaries,
            callbacks,
            callbackDescriptors,
            bindingDeclareHeaders,
            bindingHeaders,
            prefix,
            curr,
            config,
            jsImplemented,
        )

        # Add include guards.
        curr = CGIncludeGuard(prefix, curr)

        # Add the auto-generated comment.
        curr = CGWrapper(
            curr,
            pre=(
                AUTOGENERATED_WITH_SOURCE_WARNING_COMMENT % os.path.basename(webIDLFile)
            ),
        )

        # Store the final result.
        self.root = curr

    def declare(self):
        return stripTrailingWhitespace(self.root.declare())

    def define(self):
        return stripTrailingWhitespace(self.root.define())

    def deps(self):
        return self.root.deps()


class CGNativeMember(ClassMethod):
    def __init__(
        self,
        descriptorProvider,
        member,
        name,
        signature,
        extendedAttrs,
        breakAfter=True,
        passJSBitsAsNeeded=True,
        visibility="public",
        spiderMonkeyInterfacesAreStructs=True,
        variadicIsSequence=False,
        resultNotAddRefed=False,
        virtual=False,
        override=False,
        canRunScript=False,
    ):
        """
        If spiderMonkeyInterfacesAreStructs is false, SpiderMonkey interfaces
        will be passed as JS::Handle<JSObject*>.  If it's true they will be
        passed as one of the dom::SpiderMonkeyInterfaceObjectStorage subclasses.

        If passJSBitsAsNeeded is false, we don't automatically pass in a
        JSContext* or a JSObject* based on the return and argument types.  We
        can still pass it based on 'implicitJSContext' annotations.
        """
        self.descriptorProvider = descriptorProvider
        self.member = member
        self.extendedAttrs = extendedAttrs
        self.resultAlreadyAddRefed = not resultNotAddRefed
        self.passJSBitsAsNeeded = passJSBitsAsNeeded
        self.spiderMonkeyInterfacesAreStructs = spiderMonkeyInterfacesAreStructs
        self.variadicIsSequence = variadicIsSequence
        breakAfterSelf = "\n" if breakAfter else ""
        ClassMethod.__init__(
            self,
            name,
            self.getReturnType(signature[0], False),
            self.getArgs(signature[0], signature[1]),
            static=member.isStatic(),
            # Mark our getters, which are attrs that
            # have a non-void return type, as const.
            const=(
                not member.isStatic()
                and member.isAttr()
                and not signature[0].isUndefined()
            ),
            breakAfterReturnDecl=" ",
            breakAfterSelf=breakAfterSelf,
            visibility=visibility,
            virtual=virtual,
            override=override,
            canRunScript=canRunScript,
        )

    def getReturnType(self, type, isMember):
        return self.getRetvalInfo(type, isMember)[0]

    def getRetvalInfo(self, type, isMember):
        """
        Returns a tuple:

        The first element is the type declaration for the retval

        The second element is a default value that can be used on error returns.
        For cases whose behavior depends on isMember, the second element will be
        None if isMember is true.

        The third element is a template for actually returning a value stored in
        "${declName}" and "${holderName}".  This means actually returning it if
        we're not outparam, else assigning to the "retval" outparam.  If
        isMember is true, this can be None, since in that case the caller will
        never examine this value.
        """
        if type.isUndefined():
            return "void", "", ""
        if type.isPrimitive() and type.tag() in builtinNames:
            result = CGGeneric(builtinNames[type.tag()])
            defaultReturnArg = "0"
            if type.nullable():
                result = CGTemplatedType("Nullable", result)
                defaultReturnArg = ""
            return (
                result.define(),
                "%s(%s)" % (result.define(), defaultReturnArg),
                "return ${declName};\n",
            )
        if type.isJSString():
            if isMember:
                raise TypeError("JSString not supported as return type member")
            # Outparam
            return "void", "", "aRetVal.set(${declName});\n"
        if type.isDOMString() or type.isUSVString():
            if isMember:
                # No need for a third element in the isMember case
                return "nsString", None, None
            # Outparam
            return "void", "", "aRetVal = ${declName};\n"
        if type.isByteString() or type.isUTF8String():
            if isMember:
                # No need for a third element in the isMember case
                return "nsCString", None, None
            # Outparam
            return "void", "", "aRetVal = ${declName};\n"
        if type.isEnum():
            enumName = type.unroll().inner.identifier.name
            if type.nullable():
                enumName = CGTemplatedType("Nullable", CGGeneric(enumName)).define()
                defaultValue = "%s()" % enumName
            else:
                defaultValue = "%s(0)" % enumName
            return enumName, defaultValue, "return ${declName};\n"
        if type.isGeckoInterface() or type.isPromise():
            if type.isGeckoInterface():
                iface = type.unroll().inner
                result = CGGeneric(
                    self.descriptorProvider.getDescriptor(
                        iface.identifier.name
                    ).prettyNativeType
                )
            else:
                result = CGGeneric("Promise")
            if self.resultAlreadyAddRefed:
                if isMember:
                    holder = "RefPtr"
                else:
                    holder = "already_AddRefed"
                if memberReturnsNewObject(self.member) or isMember:
                    warning = ""
                else:
                    warning = "// Return a raw pointer here to avoid refcounting, but make sure it's safe (the object should be kept alive by the callee).\n"
                result = CGWrapper(result, pre=("%s%s<" % (warning, holder)), post=">")
            else:
                result = CGWrapper(result, post="*")
            # Since we always force an owning type for callback return values,
            # our ${declName} is an OwningNonNull or RefPtr.  So we can just
            # .forget() to get our already_AddRefed.
            return result.define(), "nullptr", "return ${declName}.forget();\n"
        if type.isCallback():
            return (
                "already_AddRefed<%s>" % type.unroll().callback.identifier.name,
                "nullptr",
                "return ${declName}.forget();\n",
            )
        if type.isAny():
            if isMember:
                # No need for a third element in the isMember case
                return "JS::Value", None, None
            # Outparam
            return "void", "", "aRetVal.set(${declName});\n"

        if type.isObject():
            if isMember:
                # No need for a third element in the isMember case
                return "JSObject*", None, None
            return "void", "", "aRetVal.set(${declName});\n"
        if type.isSpiderMonkeyInterface():
            if isMember:
                # No need for a third element in the isMember case
                return "JSObject*", None, None
            if type.nullable():
                returnCode = (
                    "${declName}.IsNull() ? nullptr : ${declName}.Value().Obj()"
                )
            else:
                returnCode = "${declName}.Obj()"
            return "void", "", "aRetVal.set(%s);\n" % returnCode
        if type.isSequence():
            # If we want to handle sequence-of-sequences return values, we're
            # going to need to fix example codegen to not produce nsTArray<void>
            # for the relevant argument...
            assert not isMember
            # Outparam.
            if type.nullable():
                returnCode = dedent(
                    """
                    if (${declName}.IsNull()) {
                      aRetVal.SetNull();
                    } else {
                      aRetVal.SetValue() = std::move(${declName}.Value());
                    }
                    """
                )
            else:
                returnCode = "aRetVal = std::move(${declName});\n"
            return "void", "", returnCode
        if type.isRecord():
            # If we want to handle record-of-record return values, we're
            # going to need to fix example codegen to not produce record<void>
            # for the relevant argument...
            assert not isMember
            # In this case we convert directly into our outparam to start with
            return "void", "", ""
        if type.isDictionary():
            if isMember:
                # Only the first member of the tuple matters here, but return
                # bogus values for the others in case someone decides to use
                # them.
                return CGDictionary.makeDictionaryName(type.inner), None, None
            # In this case we convert directly into our outparam to start with
            return "void", "", ""
        if type.isUnion():
            if isMember:
                # Only the first member of the tuple matters here, but return
                # bogus values for the others in case someone decides to use
                # them.
                return CGUnionStruct.unionTypeDecl(type, True), None, None
            # In this case we convert directly into our outparam to start with
            return "void", "", ""

        raise TypeError("Don't know how to declare return value for %s" % type)

    def getArgs(self, returnType, argList):
        args = [self.getArg(arg) for arg in argList]
        # Now the outparams
        if returnType.isJSString():
            args.append(Argument("JS::MutableHandle<JSString*>", "aRetVal"))
        elif returnType.isDOMString() or returnType.isUSVString():
            args.append(Argument("nsString&", "aRetVal"))
        elif returnType.isByteString() or returnType.isUTF8String():
            args.append(Argument("nsCString&", "aRetVal"))
        elif returnType.isSequence():
            nullable = returnType.nullable()
            if nullable:
                returnType = returnType.inner
            # And now the actual underlying type
            elementDecl = self.getReturnType(returnType.inner, True)
            type = CGTemplatedType("nsTArray", CGGeneric(elementDecl))
            if nullable:
                type = CGTemplatedType("Nullable", type)
            args.append(Argument("%s&" % type.define(), "aRetVal"))
        elif returnType.isRecord():
            nullable = returnType.nullable()
            if nullable:
                returnType = returnType.inner
            # And now the actual underlying type
            elementDecl = self.getReturnType(returnType.inner, True)
            type = CGTemplatedType(
                "Record", [recordKeyDeclType(returnType), CGGeneric(elementDecl)]
            )
            if nullable:
                type = CGTemplatedType("Nullable", type)
            args.append(Argument("%s&" % type.define(), "aRetVal"))
        elif returnType.isDictionary():
            nullable = returnType.nullable()
            if nullable:
                returnType = returnType.inner
            dictType = CGGeneric(CGDictionary.makeDictionaryName(returnType.inner))
            if nullable:
                dictType = CGTemplatedType("Nullable", dictType)
            args.append(Argument("%s&" % dictType.define(), "aRetVal"))
        elif returnType.isUnion():
            args.append(
                Argument(
                    "%s&" % CGUnionStruct.unionTypeDecl(returnType, True), "aRetVal"
                )
            )
        elif returnType.isAny():
            args.append(Argument("JS::MutableHandle<JS::Value>", "aRetVal"))
        elif returnType.isObject() or returnType.isSpiderMonkeyInterface():
            args.append(Argument("JS::MutableHandle<JSObject*>", "aRetVal"))

        # And the nsIPrincipal
        if "needsSubjectPrincipal" in self.extendedAttrs:
            if "needsNonSystemSubjectPrincipal" in self.extendedAttrs:
                args.append(Argument("nsIPrincipal*", "aPrincipal"))
            else:
                args.append(Argument("nsIPrincipal&", "aPrincipal"))
        # And the caller type, if desired.
        if needsCallerType(self.member):
            args.append(Argument("CallerType", "aCallerType"))
        # And the ErrorResult or OOMReporter
        if "needsErrorResult" in self.extendedAttrs:
            # Use aRv so it won't conflict with local vars named "rv"
            args.append(Argument("ErrorResult&", "aRv"))
        elif "canOOM" in self.extendedAttrs:
            args.append(Argument("OOMReporter&", "aRv"))

        # The legacycaller thisval
        if self.member.isMethod() and self.member.isLegacycaller():
            # If it has an identifier, we can't deal with it yet
            assert self.member.isIdentifierLess()
            args.insert(0, Argument("const JS::Value&", "aThisVal"))
        # And jscontext bits.
        if needCx(
            returnType,
            argList,
            self.extendedAttrs,
            self.passJSBitsAsNeeded,
            self.member.isStatic(),
        ):
            args.insert(0, Argument("JSContext*", "cx"))
            if needScopeObject(
                returnType,
                argList,
                self.extendedAttrs,
                self.descriptorProvider.wrapperCache,
                self.passJSBitsAsNeeded,
                self.member.getExtendedAttribute("StoreInSlot"),
            ):
                args.insert(1, Argument("JS::Handle<JSObject*>", "obj"))
        # And if we're static, a global
        if self.member.isStatic():
            args.insert(0, Argument("const GlobalObject&", "global"))
        return args

    def doGetArgType(self, type, optional, isMember):
        """
        The main work of getArgType.  Returns a string type decl, whether this
        is a const ref, as well as whether the type should be wrapped in
        Nullable as needed.

        isMember can be false or one of the strings "Sequence", "Variadic",
                 "Record"
        """
        if type.isSequence():
            nullable = type.nullable()
            if nullable:
                type = type.inner
            elementType = type.inner
            argType = self.getArgType(elementType, False, "Sequence")[0]
            decl = CGTemplatedType("Sequence", argType)
            return decl.define(), True, True

        if type.isRecord():
            nullable = type.nullable()
            if nullable:
                type = type.inner
            elementType = type.inner
            argType = self.getArgType(elementType, False, "Record")[0]
            decl = CGTemplatedType("Record", [recordKeyDeclType(type), argType])
            return decl.define(), True, True

        if type.isUnion():
            # unionTypeDecl will handle nullable types, so return False for
            # auto-wrapping in Nullable
            return CGUnionStruct.unionTypeDecl(type, isMember), True, False

        if type.isPromise():
            assert not type.nullable()
            if optional or isMember:
                typeDecl = "OwningNonNull<Promise>"
            else:
                typeDecl = "Promise&"
            return (typeDecl, False, False)

        if type.isGeckoInterface() and not type.isCallbackInterface():
            iface = type.unroll().inner
            if iface.identifier.name == "WindowProxy":
                return "WindowProxyHolder", True, False

            argIsPointer = type.nullable() or iface.isExternal()
            forceOwningType = iface.isCallback() or isMember
            if argIsPointer:
                if (optional or isMember) and forceOwningType:
                    typeDecl = "RefPtr<%s>"
                else:
                    typeDecl = "%s*"
            else:
                if optional or isMember:
                    if forceOwningType:
                        typeDecl = "OwningNonNull<%s>"
                    else:
                        typeDecl = "NonNull<%s>"
                else:
                    typeDecl = "%s&"
            return (
                (
                    typeDecl
                    % self.descriptorProvider.getDescriptor(
                        iface.identifier.name
                    ).prettyNativeType
                ),
                False,
                False,
            )

        if type.isSpiderMonkeyInterface():
            if not self.spiderMonkeyInterfacesAreStructs:
                return "JS::Handle<JSObject*>", False, False

            # Unroll for the name, in case we're nullable.
            return type.unroll().name, True, True

        if type.isJSString():
            if isMember:
                raise TypeError("JSString not supported as member")
            return "JS::Handle<JSString*>", False, False

        if type.isDOMString() or type.isUSVString():
            if isMember:
                declType = "nsString"
            else:
                declType = "nsAString"
            return declType, True, False

        if type.isByteString() or type.isUTF8String():
            # TODO(emilio): Maybe bytestrings could benefit from nsAutoCString
            # or such too.
            if type.isUTF8String() and not isMember:
                declType = "nsACString"
            else:
                declType = "nsCString"
            return declType, True, False

        if type.isEnum():
            return type.unroll().inner.identifier.name, False, True

        if type.isCallback() or type.isCallbackInterface():
            forceOwningType = optional or isMember
            if type.nullable():
                if forceOwningType:
                    declType = "RefPtr<%s>"
                else:
                    declType = "%s*"
            else:
                if forceOwningType:
                    declType = "OwningNonNull<%s>"
                else:
                    declType = "%s&"
            if type.isCallback():
                name = type.unroll().callback.identifier.name
            else:
                name = type.unroll().inner.identifier.name
            return declType % name, False, False

        if type.isAny():
            # Don't do the rooting stuff for variadics for now
            if isMember:
                declType = "JS::Value"
            else:
                declType = "JS::Handle<JS::Value>"
            return declType, False, False

        if type.isObject():
            if isMember:
                declType = "JSObject*"
            else:
                declType = "JS::Handle<JSObject*>"
            return declType, False, False

        if type.isDictionary():
            typeName = CGDictionary.makeDictionaryName(type.inner)
            return typeName, True, True

        assert type.isPrimitive()

        return builtinNames[type.tag()], False, True

    def getArgType(self, type, optional, isMember):
        """
        Get the type of an argument declaration.  Returns the type CGThing, and
        whether this should be a const ref.

        isMember can be False, "Sequence", or "Variadic"
        """
        decl, ref, handleNullable = self.doGetArgType(type, optional, isMember)
        decl = CGGeneric(decl)
        if handleNullable and type.nullable():
            decl = CGTemplatedType("Nullable", decl)
            ref = True
        if isMember == "Variadic":
            arrayType = "Sequence" if self.variadicIsSequence else "nsTArray"
            decl = CGTemplatedType(arrayType, decl)
            ref = True
        elif optional:
            # Note: All variadic args claim to be optional, but we can just use
            # empty arrays to represent them not being present.
            decl = CGTemplatedType("Optional", decl)
            ref = True
        return (decl, ref)

    def getArg(self, arg):
        """
        Get the full argument declaration for an argument
        """
        decl, ref = self.getArgType(
            arg.type, arg.canHaveMissingValue(), "Variadic" if arg.variadic else False
        )
        if ref:
            decl = CGWrapper(decl, pre="const ", post="&")

        return Argument(decl.define(), arg.identifier.name)

    def arguments(self):
        return self.member.signatures()[0][1]


class CGExampleMethod(CGNativeMember):
    def __init__(self, descriptor, method, signature, isConstructor, breakAfter=True):
        CGNativeMember.__init__(
            self,
            descriptor,
            method,
            CGSpecializedMethod.makeNativeName(descriptor, method),
            signature,
            descriptor.getExtendedAttributes(method),
            breakAfter=breakAfter,
            variadicIsSequence=True,
        )

    def declare(self, cgClass):
        assert self.member.isMethod()
        # We skip declaring ourselves if this is a maplike/setlike/iterable
        # method, because those get implemented automatically by the binding
        # machinery, so the implementor of the interface doesn't have to worry
        # about it.
        if self.member.isMaplikeOrSetlikeOrIterableMethod():
            return ""
        return CGNativeMember.declare(self, cgClass)

    def define(self, cgClass):
        return ""


class CGExampleGetter(CGNativeMember):
    def __init__(self, descriptor, attr):
        CGNativeMember.__init__(
            self,
            descriptor,
            attr,
            CGSpecializedGetterCommon.makeNativeName(descriptor, attr),
            (attr.type, []),
            descriptor.getExtendedAttributes(attr, getter=True),
        )

    def getArgs(self, returnType, argList):
        args = CGNativeMember.getArgs(self, returnType, argList)
        if self.member.getExtendedAttribute(
            "ReflectedHTMLAttributeReturningFrozenArray"
        ):
            args.insert(0, Argument("bool*", "aUseCachedValue"))
        return args

    def declare(self, cgClass):
        assert self.member.isAttr()
        # We skip declaring ourselves if this is a maplike/setlike attr (in
        # practice, "size"), because those get implemented automatically by the
        # binding machinery, so the implementor of the interface doesn't have to
        # worry about it.
        if self.member.isMaplikeOrSetlikeAttr():
            return ""
        return CGNativeMember.declare(self, cgClass)

    def define(self, cgClass):
        return ""


class CGExampleSetter(CGNativeMember):
    def __init__(self, descriptor, attr):
        CGNativeMember.__init__(
            self,
            descriptor,
            attr,
            CGSpecializedSetterCommon.makeNativeName(descriptor, attr),
            (
                BuiltinTypes[IDLBuiltinType.Types.undefined],
                [FakeArgument(attr.type)],
            ),
            descriptor.getExtendedAttributes(attr, setter=True),
        )

    def define(self, cgClass):
        return ""


class CGBindingImplClass(CGClass):
    """
    Common codegen for generating a C++ implementation of a WebIDL interface
    """

    def __init__(
        self,
        descriptor,
        cgMethod,
        cgGetter,
        cgSetter,
        wantGetParent=True,
        wrapMethodName="WrapObject",
        skipStaticMethods=False,
    ):
        """
        cgMethod, cgGetter and cgSetter are classes used to codegen methods,
        getters and setters.
        """
        self.descriptor = descriptor
        self._deps = descriptor.interface.getDeps()

        iface = descriptor.interface

        self.methodDecls = []

        def appendMethod(m, isConstructor=False):
            sigs = m.signatures()
            for s in sigs[:-1]:
                # Don't put a blank line after overloads, until we
                # get to the last one.
                self.methodDecls.append(
                    cgMethod(descriptor, m, s, isConstructor, breakAfter=False)
                )
            self.methodDecls.append(cgMethod(descriptor, m, sigs[-1], isConstructor))

        if iface.ctor():
            appendMethod(iface.ctor(), isConstructor=True)
        for n in iface.legacyFactoryFunctions:
            appendMethod(n, isConstructor=True)
        for m in iface.members:
            if m.isMethod():
                if m.isIdentifierLess():
                    continue
                if m.isMaplikeOrSetlikeOrIterableMethod():
                    # Handled by generated code already
                    continue
                if not m.isStatic() or not skipStaticMethods:
                    appendMethod(m)
            elif m.isAttr():
                if m.isMaplikeOrSetlikeAttr() or m.type.isObservableArray():
                    # Handled by generated code already
                    continue
                self.methodDecls.append(cgGetter(descriptor, m))
                if not m.readonly:
                    self.methodDecls.append(cgSetter(descriptor, m))

        # Now do the special operations
        def appendSpecialOperation(name, op):
            if op is None:
                return
            assert len(op.signatures()) == 1
            returnType, args = op.signatures()[0]
            # Make a copy of the args, since we plan to modify them.
            args = list(args)
            if op.isGetter() or op.isDeleter():
                # This is a total hack.  The '&' belongs with the
                # type, not the name!  But it works, and is simpler
                # than trying to somehow make this pretty.
                args.append(
                    FakeArgument(
                        BuiltinTypes[IDLBuiltinType.Types.boolean], name="&found"
                    )
                )
            if name == "Stringifier":
                if op.isIdentifierLess():
                    # XXXbz I wish we were consistent about our renaming here.
                    name = "Stringify"
                else:
                    # We already added this method
                    return
            if name == "LegacyCaller":
                if op.isIdentifierLess():
                    # XXXbz I wish we were consistent about our renaming here.
                    name = "LegacyCall"
                else:
                    # We already added this method
                    return
            self.methodDecls.append(
                CGNativeMember(
                    descriptor,
                    op,
                    name,
                    (returnType, args),
                    descriptor.getExtendedAttributes(op),
                )
            )

        # Sort things by name so we get stable ordering in the output.
        ops = sorted(descriptor.operations.items(), key=lambda x: x[0])
        for name, op in ops:
            appendSpecialOperation(name, op)
        # If we support indexed properties, then we need a Length()
        # method so we know which indices are supported.
        if descriptor.supportsIndexedProperties():
            # But we don't need it if we already have an infallible
            # "length" attribute, which we often do.
            haveLengthAttr = any(
                m
                for m in iface.members
                if m.isAttr()
                and CGSpecializedGetterCommon.makeNativeName(descriptor, m) == "Length"
            )
            if not haveLengthAttr:
                self.methodDecls.append(
                    CGNativeMember(
                        descriptor,
                        FakeMember(),
                        "Length",
                        (BuiltinTypes[IDLBuiltinType.Types.unsigned_long], []),
                        [],
                    ),
                )
        # And if we support named properties we need to be able to
        # enumerate the supported names.
        if descriptor.supportsNamedProperties():
            self.methodDecls.append(
                CGNativeMember(
                    descriptor,
                    FakeMember(),
                    "GetSupportedNames",
                    (
                        IDLSequenceType(
                            None, BuiltinTypes[IDLBuiltinType.Types.domstring]
                        ),
                        [],
                    ),
                    [],
                )
            )

        if descriptor.concrete:
            wrapArgs = [
                Argument("JSContext*", "aCx"),
                Argument("JS::Handle<JSObject*>", "aGivenProto"),
            ]
            if not descriptor.wrapperCache:
                wrapReturnType = "bool"
                wrapArgs.append(Argument("JS::MutableHandle<JSObject*>", "aReflector"))
            else:
                wrapReturnType = "JSObject*"
            self.methodDecls.insert(
                0,
                ClassMethod(
                    wrapMethodName,
                    wrapReturnType,
                    wrapArgs,
                    virtual=descriptor.wrapperCache,
                    breakAfterReturnDecl=" ",
                    override=descriptor.wrapperCache,
                    body=self.getWrapObjectBody(),
                ),
            )
        if descriptor.hasCEReactions():
            self.methodDecls.insert(
                0,
                ClassMethod(
                    "GetDocGroup",
                    "DocGroup*",
                    [],
                    const=True,
                    breakAfterReturnDecl=" ",
                    body=self.getGetDocGroupBody(),
                ),
            )
        if wantGetParent:
            self.methodDecls.insert(
                0,
                ClassMethod(
                    "GetParentObject",
                    self.getGetParentObjectReturnType(),
                    [],
                    const=True,
                    breakAfterReturnDecl=" ",
                    body=self.getGetParentObjectBody(),
                ),
            )

        # Invoke  CGClass.__init__ in any subclasses afterwards to do the actual codegen.

    def getWrapObjectBody(self):
        return None

    def getGetParentObjectReturnType(self):
        # The lack of newline before the end of the string is on purpose.
        return dedent(
            """
            // This should return something that eventually allows finding a
            // path to the global this object is associated with.  Most simply,
            // returning an actual global works.
            nsIGlobalObject*"""
        )

    def getGetParentObjectBody(self):
        return None

    def getGetDocGroupBody(self):
        return None

    def deps(self):
        return self._deps


class CGExampleObservableArrayCallback(CGNativeMember):
    def __init__(self, descriptor, attr, callbackName):
        assert attr.isAttr()
        assert attr.type.isObservableArray()
        CGNativeMember.__init__(
            self,
            descriptor,
            attr,
            self.makeNativeName(attr, callbackName),
            (
                BuiltinTypes[IDLBuiltinType.Types.undefined],
                [
                    FakeArgument(attr.type.inner, "aValue"),
                    FakeArgument(
                        BuiltinTypes[IDLBuiltinType.Types.unsigned_long], "aIndex"
                    ),
                ],
            ),
            ["needsErrorResult"],
        )

    def declare(self, cgClass):
        assert self.member.isAttr()
        assert self.member.type.isObservableArray()
        return CGNativeMember.declare(self, cgClass)

    def define(self, cgClass):
        return ""

    @staticmethod
    def makeNativeName(attr, callbackName):
        assert attr.isAttr()
        nativeName = MakeNativeName(attr.identifier.name)
        return "On" + callbackName + nativeName


class CGExampleClass(CGBindingImplClass):
    """
    Codegen for the actual example class implementation for this descriptor
    """

    def __init__(self, descriptor):
        CGBindingImplClass.__init__(
            self,
            descriptor,
            CGExampleMethod,
            CGExampleGetter,
            CGExampleSetter,
            wantGetParent=descriptor.wrapperCache,
        )

        self.parentIface = descriptor.interface.parent
        if self.parentIface:
            self.parentDesc = descriptor.getDescriptor(self.parentIface.identifier.name)
            bases = [ClassBase(self.nativeLeafName(self.parentDesc))]
        else:
            bases = [
                ClassBase(
                    "nsISupports /* or NonRefcountedDOMObject if this is a non-refcounted object */"
                )
            ]
            if descriptor.wrapperCache:
                bases.append(
                    ClassBase(
                        "nsWrapperCache /* Change wrapperCache in the binding configuration if you don't want this */"
                    )
                )

        destructorVisibility = "protected"
        if self.parentIface:
            extradeclarations = (
                "public:\n"
                "  NS_DECL_ISUPPORTS_INHERITED\n"
                "  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(%s, %s)\n"
                "\n"
                % (
                    self.nativeLeafName(descriptor),
                    self.nativeLeafName(self.parentDesc),
                )
            )
        else:
            extradeclarations = (
                "public:\n"
                "  NS_DECL_CYCLE_COLLECTING_ISUPPORTS\n"
                "  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(%s)\n"
                "\n" % self.nativeLeafName(descriptor)
            )

        if descriptor.interface.hasChildInterfaces():
            decorators = ""
        else:
            decorators = "final"

        for m in descriptor.interface.members:
            if m.isAttr() and m.type.isObservableArray():
                self.methodDecls.append(
                    CGExampleObservableArrayCallback(descriptor, m, "Set")
                )
                self.methodDecls.append(
                    CGExampleObservableArrayCallback(descriptor, m, "Delete")
                )

        CGClass.__init__(
            self,
            self.nativeLeafName(descriptor),
            bases=bases,
            constructors=[ClassConstructor([], visibility="public")],
            destructor=ClassDestructor(visibility=destructorVisibility),
            methods=self.methodDecls,
            decorators=decorators,
            extradeclarations=extradeclarations,
        )

    def define(self):
        # Just override CGClass and do our own thing
        nativeType = self.nativeLeafName(self.descriptor)

        ctordtor = fill(
            """
            ${nativeType}::${nativeType}()
            {
                // Add |MOZ_COUNT_CTOR(${nativeType});| for a non-refcounted object.
            }

            ${nativeType}::~${nativeType}()
            {
                // Add |MOZ_COUNT_DTOR(${nativeType});| for a non-refcounted object.
            }
            """,
            nativeType=nativeType,
        )

        if self.parentIface:
            ccImpl = fill(
                """

                // Only needed for refcounted objects.
                # error "If you don't have members that need cycle collection,
                # then remove all the cycle collection bits from this
                # implementation and the corresponding header.  If you do, you
                # want NS_IMPL_CYCLE_COLLECTION_INHERITED(${nativeType},
                # ${parentType}, your, members, here)"
                NS_IMPL_ADDREF_INHERITED(${nativeType}, ${parentType})
                NS_IMPL_RELEASE_INHERITED(${nativeType}, ${parentType})
                NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(${nativeType})
                NS_INTERFACE_MAP_END_INHERITING(${parentType})

                """,
                nativeType=nativeType,
                parentType=self.nativeLeafName(self.parentDesc),
            )
        else:
            ccImpl = fill(
                """

                // Only needed for refcounted objects.
                NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_0(${nativeType})
                NS_IMPL_CYCLE_COLLECTING_ADDREF(${nativeType})
                NS_IMPL_CYCLE_COLLECTING_RELEASE(${nativeType})
                NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(${nativeType})
                  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
                  NS_INTERFACE_MAP_ENTRY(nsISupports)
                NS_INTERFACE_MAP_END

                """,
                nativeType=nativeType,
            )

        classImpl = ccImpl + ctordtor + "\n"
        if self.descriptor.concrete:
            if self.descriptor.wrapperCache:
                reflectorArg = ""
                reflectorPassArg = ""
                returnType = "JSObject*"
            else:
                reflectorArg = ", JS::MutableHandle<JSObject*> aReflector"
                reflectorPassArg = ", aReflector"
                returnType = "bool"
            classImpl += fill(
                """
                ${returnType}
                ${nativeType}::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto${reflectorArg})
                {
                  return ${ifaceName}_Binding::Wrap(aCx, this, aGivenProto${reflectorPassArg});
                }

                """,
                returnType=returnType,
                nativeType=nativeType,
                reflectorArg=reflectorArg,
                ifaceName=self.descriptor.name,
                reflectorPassArg=reflectorPassArg,
            )

        return classImpl

    @staticmethod
    def nativeLeafName(descriptor):
        return descriptor.nativeType.split("::")[-1]


class CGExampleRoot(CGThing):
    """
    Root codegen class for example implementation generation.  Instantiate the
    class and call declare or define to generate header or cpp code,
    respectively.
    """

    def __init__(self, config, interfaceName):
        descriptor = config.getDescriptor(interfaceName)

        self.root = CGWrapper(CGExampleClass(descriptor), pre="\n", post="\n")

        self.root = CGNamespace.build(["mozilla", "dom"], self.root)

        builder = ForwardDeclarationBuilder()
        if descriptor.hasCEReactions():
            builder.addInMozillaDom("DocGroup")
        for member in descriptor.interface.members:
            if not member.isAttr() and not member.isMethod():
                continue
            if member.isStatic():
                builder.addInMozillaDom("GlobalObject")
            if member.isAttr():
                if not member.isMaplikeOrSetlikeAttr():
                    builder.forwardDeclareForType(member.type, config)
            else:
                assert member.isMethod()
                if not member.isMaplikeOrSetlikeOrIterableMethod():
                    for sig in member.signatures():
                        builder.forwardDeclareForType(sig[0], config)
                        for arg in sig[1]:
                            builder.forwardDeclareForType(arg.type, config)

        self.root = CGList([builder.build(), self.root], "\n")

        # Throw in our #includes
        self.root = CGHeaders(
            [],
            [],
            [],
            [],
            [
                "nsWrapperCache.h",
                "nsCycleCollectionParticipant.h",
                "mozilla/Attributes.h",
                "mozilla/ErrorResult.h",
                "mozilla/dom/BindingDeclarations.h",
                "js/TypeDecls.h",
            ],
            [
                "mozilla/dom/%s.h" % interfaceName,
                (
                    "mozilla/dom/%s"
                    % CGHeaders.getDeclarationFilename(descriptor.interface)
                ),
            ],
            "",
            self.root,
        )

        # And now some include guards
        self.root = CGIncludeGuard(interfaceName, self.root)

        # And our license block comes before everything else
        self.root = CGWrapper(
            self.root,
            pre=dedent(
                """
            /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
            /* vim:set ts=2 sw=2 sts=2 et cindent: */
            /* This Source Code Form is subject to the terms of the Mozilla Public
             * License, v. 2.0. If a copy of the MPL was not distributed with this
             * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

            """
            ),
        )

    def declare(self):
        return self.root.declare()

    def define(self):
        return self.root.define()


def jsImplName(name):
    return name + "JSImpl"


class CGJSImplMember(CGNativeMember):
    """
    Base class for generating code for the members of the implementation class
    for a JS-implemented WebIDL interface.
    """

    def __init__(
        self,
        descriptorProvider,
        member,
        name,
        signature,
        extendedAttrs,
        breakAfter=True,
        passJSBitsAsNeeded=True,
        visibility="public",
        variadicIsSequence=False,
        virtual=False,
        override=False,
    ):
        CGNativeMember.__init__(
            self,
            descriptorProvider,
            member,
            name,
            signature,
            extendedAttrs,
            breakAfter=breakAfter,
            passJSBitsAsNeeded=passJSBitsAsNeeded,
            visibility=visibility,
            variadicIsSequence=variadicIsSequence,
            virtual=virtual,
            override=override,
        )
        self.body = self.getImpl()

    def getArgs(self, returnType, argList):
        args = CGNativeMember.getArgs(self, returnType, argList)
        args.append(Argument("JS::Realm*", "aRealm", "nullptr"))
        return args


class CGJSImplMethod(CGJSImplMember):
    """
    Class for generating code for the methods for a JS-implemented WebIDL
    interface.
    """

    def __init__(self, descriptor, method, signature, isConstructor, breakAfter=True):
        self.signature = signature
        self.descriptor = descriptor
        self.isConstructor = isConstructor
        CGJSImplMember.__init__(
            self,
            descriptor,
            method,
            CGSpecializedMethod.makeNativeName(descriptor, method),
            signature,
            descriptor.getExtendedAttributes(method),
            breakAfter=breakAfter,
            variadicIsSequence=True,
            passJSBitsAsNeeded=False,
        )

    def getArgs(self, returnType, argList):
        if self.isConstructor:
            # Skip the JS::Compartment bits for constructors; it's handled
            # manually in getImpl.  But we do need our aGivenProto argument.  We
            # allow it to be omitted if the default proto is desired.
            return CGNativeMember.getArgs(self, returnType, argList) + [
                Argument("JS::Handle<JSObject*>", "aGivenProto", "nullptr")
            ]
        return CGJSImplMember.getArgs(self, returnType, argList)

    def getImpl(self):
        args = self.getArgs(self.signature[0], self.signature[1])
        if not self.isConstructor:
            return "return mImpl->%s(%s);\n" % (
                self.name,
                ", ".join(arg.name for arg in args),
            )

        assert self.descriptor.interface.isJSImplemented()
        if self.name != "Constructor":
            raise TypeError(
                "Legacy factory functions are not supported for JS implemented WebIDL."
            )
        if len(self.signature[1]) != 0:
            # The first two arguments to the constructor implementation are not
            # arguments to the WebIDL constructor, so don't pass them to
            # __Init().  The last argument is the prototype we're supposed to
            # use, and shouldn't get passed to __Init() either.
            assert args[0].argType == "const GlobalObject&"
            assert args[1].argType == "JSContext*"
            assert args[-1].argType == "JS::Handle<JSObject*>"
            assert args[-1].name == "aGivenProto"
            constructorArgs = [arg.name for arg in args[2:-1]]
            constructorArgs.append("js::GetNonCCWObjectRealm(scopeObj)")
            initCall = fill(
                """
                // Wrap the object before calling __Init so that __DOM_IMPL__ is available.
                JS::Rooted<JSObject*> scopeObj(cx, global.Get());
                MOZ_ASSERT(js::IsObjectInContextCompartment(scopeObj, cx));
                JS::Rooted<JS::Value> wrappedVal(cx);
                if (!GetOrCreateDOMReflector(cx, impl, &wrappedVal, aGivenProto)) {
                  MOZ_ASSERT(JS_IsExceptionPending(cx));
                  aRv.Throw(NS_ERROR_UNEXPECTED);
                  return nullptr;
                }
                // Initialize the object with the constructor arguments.
                impl->mImpl->__Init(${args});
                if (aRv.Failed()) {
                  return nullptr;
                }
                """,
                args=", ".join(constructorArgs),
            )
        else:
            initCall = ""
        return fill(
            """
            RefPtr<${implClass}> impl =
              ConstructJSImplementation<${implClass}>("${contractId}", global, aRv);
            if (aRv.Failed()) {
              return nullptr;
            }
            $*{initCall}
            return impl.forget();
            """,
            contractId=self.descriptor.interface.getJSImplementation(),
            implClass=self.descriptor.name,
            initCall=initCall,
        )


# We're always fallible
def callbackGetterName(attr, descriptor):
    return "Get" + MakeNativeName(
        descriptor.binaryNameFor(attr.identifier.name, attr.isStatic())
    )


def callbackSetterName(attr, descriptor):
    return "Set" + MakeNativeName(
        descriptor.binaryNameFor(attr.identifier.name, attr.isStatic())
    )


class CGJSImplGetter(CGJSImplMember):
    """
    Class for generating code for the getters of attributes for a JS-implemented
    WebIDL interface.
    """

    def __init__(self, descriptor, attr):
        CGJSImplMember.__init__(
            self,
            descriptor,
            attr,
            CGSpecializedGetterCommon.makeNativeName(descriptor, attr),
            (attr.type, []),
            descriptor.getExtendedAttributes(attr, getter=True),
            passJSBitsAsNeeded=False,
        )

    def getImpl(self):
        callbackArgs = [arg.name for arg in self.getArgs(self.member.type, [])]
        return "return mImpl->%s(%s);\n" % (
            callbackGetterName(self.member, self.descriptorProvider),
            ", ".join(callbackArgs),
        )


class CGJSImplSetter(CGJSImplMember):
    """
    Class for generating code for the setters of attributes for a JS-implemented
    WebIDL interface.
    """

    def __init__(self, descriptor, attr):
        CGJSImplMember.__init__(
            self,
            descriptor,
            attr,
            CGSpecializedSetterCommon.makeNativeName(descriptor, attr),
            (
                BuiltinTypes[IDLBuiltinType.Types.undefined],
                [FakeArgument(attr.type)],
            ),
            descriptor.getExtendedAttributes(attr, setter=True),
            passJSBitsAsNeeded=False,
        )

    def getImpl(self):
        callbackArgs = [
            arg.name
            for arg in self.getArgs(
                BuiltinTypes[IDLBuiltinType.Types.undefined],
                [FakeArgument(self.member.type)],
            )
        ]
        return "mImpl->%s(%s);\n" % (
            callbackSetterName(self.member, self.descriptorProvider),
            ", ".join(callbackArgs),
        )


class CGJSImplClass(CGBindingImplClass):
    def __init__(self, descriptor):
        CGBindingImplClass.__init__(
            self,
            descriptor,
            CGJSImplMethod,
            CGJSImplGetter,
            CGJSImplSetter,
            skipStaticMethods=True,
        )

        if descriptor.interface.parent:
            parentClass = descriptor.getDescriptor(
                descriptor.interface.parent.identifier.name
            ).jsImplParent
            baseClasses = [ClassBase(parentClass)]
            isupportsDecl = "NS_DECL_ISUPPORTS_INHERITED\n"
            ccDecl = "NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(%s, %s)\n" % (
                descriptor.name,
                parentClass,
            )
            extradefinitions = fill(
                """
                NS_IMPL_CYCLE_COLLECTION_INHERITED(${ifaceName}, ${parentClass}, mImpl, mParent)
                NS_IMPL_ADDREF_INHERITED(${ifaceName}, ${parentClass})
                NS_IMPL_RELEASE_INHERITED(${ifaceName}, ${parentClass})
                NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(${ifaceName})
                NS_INTERFACE_MAP_END_INHERITING(${parentClass})
                """,
                ifaceName=self.descriptor.name,
                parentClass=parentClass,
            )
        else:
            baseClasses = [
                ClassBase("nsSupportsWeakReference"),
                ClassBase("nsWrapperCache"),
            ]
            isupportsDecl = "NS_DECL_CYCLE_COLLECTING_ISUPPORTS\n"
            ccDecl = (
                "NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(%s)\n" % descriptor.name
            )
            extradefinitions = fill(
                """
                NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(${ifaceName})
                NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(${ifaceName})
                  NS_IMPL_CYCLE_COLLECTION_UNLINK(mImpl)
                  NS_IMPL_CYCLE_COLLECTION_UNLINK(mParent)
                  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
                  tmp->ClearWeakReferences();
                NS_IMPL_CYCLE_COLLECTION_UNLINK_END
                NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(${ifaceName})
                  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mImpl)
                  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mParent)
                NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
                NS_IMPL_CYCLE_COLLECTING_ADDREF(${ifaceName})
                NS_IMPL_CYCLE_COLLECTING_RELEASE(${ifaceName})
                NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(${ifaceName})
                  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
                  NS_INTERFACE_MAP_ENTRY(nsISupports)
                  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
                NS_INTERFACE_MAP_END
                """,
                ifaceName=self.descriptor.name,
            )

        extradeclarations = fill(
            """
            public:
              $*{isupportsDecl}
              $*{ccDecl}

            private:
              RefPtr<${jsImplName}> mImpl;
              nsCOMPtr<nsIGlobalObject> mParent;

            """,
            isupportsDecl=isupportsDecl,
            ccDecl=ccDecl,
            jsImplName=jsImplName(descriptor.name),
        )

        if descriptor.interface.getExtendedAttribute("WantsEventListenerHooks"):
            # No need to do too much sanity checking here; the
            # generated code will fail to compile if the methods we
            # try to overrid aren't on a superclass.
            self.methodDecls.extend(
                self.getEventHookMethod(parentClass, "EventListenerAdded")
            )
            self.methodDecls.extend(
                self.getEventHookMethod(parentClass, "EventListenerRemoved")
            )

        if descriptor.interface.hasChildInterfaces():
            decorators = ""
            # We need a protected virtual destructor our subclasses can use
            destructor = ClassDestructor(virtual=True, visibility="protected")
        else:
            decorators = "final"
            destructor = ClassDestructor(virtual=False, visibility="private")

        baseConstructors = [
            (
                "mImpl(new %s(nullptr, aJSImplObject, aJSImplGlobal, /* aIncumbentGlobal = */ nullptr))"
                % jsImplName(descriptor.name)
            ),
            "mParent(aParent)",
        ]
        parentInterface = descriptor.interface.parent
        while parentInterface:
            if parentInterface.isJSImplemented():
                baseConstructors.insert(
                    0, "%s(aJSImplObject, aJSImplGlobal, aParent)" % parentClass
                )
                break
            parentInterface = parentInterface.parent
        if not parentInterface and descriptor.interface.parent:
            # We only have C++ ancestors, so only pass along the window
            baseConstructors.insert(0, "%s(aParent)" % parentClass)

        constructor = ClassConstructor(
            [
                Argument("JS::Handle<JSObject*>", "aJSImplObject"),
                Argument("JS::Handle<JSObject*>", "aJSImplGlobal"),
                Argument("nsIGlobalObject*", "aParent"),
            ],
            visibility="public",
            baseConstructors=baseConstructors,
        )

        self.methodDecls.append(
            ClassMethod(
                "_Create",
                "bool",
                JSNativeArguments(),
                static=True,
                body=self.getCreateFromExistingBody(),
            )
        )

        CGClass.__init__(
            self,
            descriptor.name,
            bases=baseClasses,
            constructors=[constructor],
            destructor=destructor,
            methods=self.methodDecls,
            decorators=decorators,
            extradeclarations=extradeclarations,
            extradefinitions=extradefinitions,
        )

    def getWrapObjectBody(self):
        return fill(
            """
            JS::Rooted<JSObject*> obj(aCx, ${name}_Binding::Wrap(aCx, this, aGivenProto));
            if (!obj) {
              return nullptr;
            }

            // Now define it on our chrome object
            JSAutoRealm ar(aCx, mImpl->CallbackGlobalOrNull());
            if (!JS_WrapObject(aCx, &obj)) {
              return nullptr;
            }
            JS::Rooted<JSObject*> callback(aCx, mImpl->CallbackOrNull());
            if (!JS_DefineProperty(aCx, callback, "__DOM_IMPL__", obj, 0)) {
              return nullptr;
            }
            return obj;
            """,
            name=self.descriptor.name,
        )

    def getGetParentObjectReturnType(self):
        return "nsISupports*"

    def getGetParentObjectBody(self):
        return "return mParent;\n"

    def getGetDocGroupBody(self):
        return dedent(
            """
            nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(mParent);
            if (!window) {
              return nullptr;
            }
            return window->GetDocGroup();
            """
        )

    def getCreateFromExistingBody(self):
        # XXXbz we could try to get parts of this (e.g. the argument
        # conversions) auto-generated by somehow creating an IDLMethod and
        # adding it to our interface, but we'd still need to special-case the
        # implementation slightly to have it not try to forward to the JS
        # object...
        return fill(
            """
            JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
            if (!args.requireAtLeast(cx, "${ifaceName}._create", 2)) {
              return false;
            }
            BindingCallContext callCx(cx, "${ifaceName}._create");
            if (!args[0].isObject()) {
              return callCx.ThrowErrorMessage<MSG_NOT_OBJECT>("Argument 1");
            }
            if (!args[1].isObject()) {
              return callCx.ThrowErrorMessage<MSG_NOT_OBJECT>("Argument 2");
            }

            // GlobalObject will go through wrappers as needed for us, and
            // is simpler than the right UnwrapArg incantation.
            GlobalObject global(cx, &args[0].toObject());
            if (global.Failed()) {
              return false;
            }
            nsCOMPtr<nsIGlobalObject> globalHolder = do_QueryInterface(global.GetAsSupports());
            MOZ_ASSERT(globalHolder);
            JS::Rooted<JSObject*> arg(cx, &args[1].toObject());
            JS::Rooted<JSObject*> argGlobal(cx, JS::CurrentGlobalOrNull(cx));
            RefPtr<${implName}> impl = new ${implName}(arg, argGlobal, globalHolder);
            MOZ_ASSERT(js::IsObjectInContextCompartment(arg, cx));
            return GetOrCreateDOMReflector(cx, impl, args.rval());
            """,
            ifaceName=self.descriptor.interface.identifier.name,
            implName=self.descriptor.name,
        )

    def getEventHookMethod(self, parentClass, methodName):
        body = fill(
            """
            ${parentClass}::${methodName}(aType);
            mImpl->${methodName}(Substring(nsDependentAtomString(aType), 2), IgnoreErrors());
            """,
            parentClass=parentClass,
            methodName=methodName,
        )
        return [
            ClassMethod(
                methodName,
                "void",
                [Argument("nsAtom*", "aType")],
                virtual=True,
                override=True,
                body=body,
            ),
            ClassUsingFromBaseDeclaration(parentClass, methodName),
        ]


def isJSImplementedDescriptor(descriptorProvider):
    return (
        isinstance(descriptorProvider, Descriptor)
        and descriptorProvider.interface.isJSImplemented()
    )


class CGCallback(CGClass):
    def __init__(
        self, idlObject, descriptorProvider, baseName, methods, getters=[], setters=[]
    ):
        self.baseName = baseName
        self._deps = idlObject.getDeps()
        self.idlObject = idlObject
        self.name = idlObject.identifier.name
        if isJSImplementedDescriptor(descriptorProvider):
            self.name = jsImplName(self.name)
        # For our public methods that needThisHandling we want most of the
        # same args and the same return type as what CallbackMember
        # generates.  So we want to take advantage of all its
        # CGNativeMember infrastructure, but that infrastructure can't deal
        # with templates and most especially template arguments.  So just
        # cheat and have CallbackMember compute all those things for us.
        realMethods = []
        for method in methods:
            if not isinstance(method, CallbackMember) or not method.needThisHandling:
                realMethods.append(method)
            else:
                realMethods.extend(self.getMethodImpls(method))
        realMethods.append(
            ClassMethod(
                "operator==",
                "bool",
                [Argument("const %s&" % self.name, "aOther")],
                inline=True,
                bodyInHeader=True,
                const=True,
                body=("return %s::operator==(aOther);\n" % baseName),
            )
        )
        CGClass.__init__(
            self,
            self.name,
            bases=[ClassBase(baseName)],
            constructors=self.getConstructors(),
            methods=realMethods + getters + setters,
        )

    def getConstructors(self):
        if (
            not self.idlObject.isInterface()
            and not self.idlObject._treatNonObjectAsNull
        ):
            body = "MOZ_ASSERT(JS::IsCallable(mCallback));\n"
        else:
            # Not much we can assert about it, other than not being null, and
            # CallbackObject does that already.
            body = ""
        return [
            ClassConstructor(
                [
                    Argument("JSContext*", "aCx"),
                    Argument("JS::Handle<JSObject*>", "aCallback"),
                    Argument("JS::Handle<JSObject*>", "aCallbackGlobal"),
                    Argument("nsIGlobalObject*", "aIncumbentGlobal"),
                ],
                bodyInHeader=True,
                visibility="public",
                explicit=True,
                baseConstructors=[
                    "%s(aCx, aCallback, aCallbackGlobal, aIncumbentGlobal)"
                    % self.baseName,
                ],
                body=body,
            ),
            ClassConstructor(
                [
                    Argument("JSObject*", "aCallback"),
                    Argument("JSObject*", "aCallbackGlobal"),
                    Argument("const FastCallbackConstructor&", ""),
                ],
                bodyInHeader=True,
                visibility="public",
                explicit=True,
                baseConstructors=[
                    "%s(aCallback, aCallbackGlobal, FastCallbackConstructor())"
                    % self.baseName,
                ],
                body=body,
            ),
            ClassConstructor(
                [
                    Argument("JSObject*", "aCallback"),
                    Argument("JSObject*", "aCallbackGlobal"),
                    Argument("JSObject*", "aAsyncStack"),
                    Argument("nsIGlobalObject*", "aIncumbentGlobal"),
                ],
                bodyInHeader=True,
                visibility="public",
                explicit=True,
                baseConstructors=[
                    "%s(aCallback, aCallbackGlobal, aAsyncStack, aIncumbentGlobal)"
                    % self.baseName,
                ],
                body=body,
            ),
        ]

    def getMethodImpls(self, method):
        assert method.needThisHandling
        args = list(method.args)
        # Strip out the BindingCallContext&/JSObject* args
        # that got added.
        assert args[0].name == "cx" and args[0].argType == "BindingCallContext&"
        assert args[1].name == "aThisVal" and args[1].argType == "JS::Handle<JS::Value>"
        args = args[2:]

        # Now remember which index the ErrorResult argument is at;
        # we'll need this below.
        assert args[-1].name == "aRv" and args[-1].argType == "ErrorResult&"
        rvIndex = len(args) - 1
        assert rvIndex >= 0

        # Record the names of all the arguments, so we can use them when we call
        # the private method.
        argnames = [arg.name for arg in args]
        argnamesWithThis = ["s.GetCallContext()", "thisValJS"] + argnames
        argnamesWithoutThis = [
            "s.GetCallContext()",
            "JS::UndefinedHandleValue",
        ] + argnames
        # Now that we've recorded the argnames for our call to our private
        # method, insert our optional argument for the execution reason.
        args.append(Argument("const char*", "aExecutionReason", "nullptr"))

        # Make copies of the arg list for the two "without rv" overloads.  Note
        # that those don't need aExceptionHandling or aRealm arguments because
        # those would make not sense anyway: the only sane thing to do with
        # exceptions in the "without rv" cases is to report them.
        argsWithoutRv = list(args)
        argsWithoutRv.pop(rvIndex)
        argsWithoutThisAndRv = list(argsWithoutRv)

        # Add the potional argument for deciding whether the CallSetup should
        # re-throw exceptions on aRv.
        args.append(
            Argument("ExceptionHandling", "aExceptionHandling", "eReportExceptions")
        )
        # And the argument for communicating when exceptions should really be
        # rethrown.  In particular, even when aExceptionHandling is
        # eRethrowExceptions they won't get rethrown if aRealm is provided
        # and its principal doesn't subsume either the callback or the
        # exception.
        args.append(Argument("JS::Realm*", "aRealm", "nullptr"))
        # And now insert our template argument.
        argsWithoutThis = list(args)
        args.insert(0, Argument("const T&", "thisVal"))
        argsWithoutRv.insert(0, Argument("const T&", "thisVal"))

        argnamesWithoutThisAndRv = [arg.name for arg in argsWithoutThisAndRv]
        argnamesWithoutThisAndRv.insert(rvIndex, "IgnoreErrors()")
        # If we just leave things like that, and have no actual arguments in the
        # IDL, we will end up trying to call the templated "without rv" overload
        # with "rv" as the thisVal.  That's no good.  So explicitly append the
        # aExceptionHandling and aRealm values we need to end up matching the
        # signature of our non-templated "with rv" overload.
        argnamesWithoutThisAndRv.extend(["eReportExceptions", "nullptr"])

        argnamesWithoutRv = [arg.name for arg in argsWithoutRv]
        # Note that we need to insert at rvIndex + 1, since we inserted a
        # thisVal arg at the start.
        argnamesWithoutRv.insert(rvIndex + 1, "IgnoreErrors()")

        errorReturn = method.getDefaultRetval()

        setupCall = fill(
            """
            MOZ_ASSERT(!aRv.Failed(), "Don't pass an already-failed ErrorResult to a callback!");
            if (!aExecutionReason) {
              aExecutionReason = "${executionReason}";
            }
            CallSetup s(this, aRv, aExecutionReason, aExceptionHandling, aRealm);
            if (!s.GetContext()) {
              MOZ_ASSERT(aRv.Failed());
              return${errorReturn};
            }
            """,
            errorReturn=errorReturn,
            executionReason=method.getPrettyName(),
        )

        bodyWithThis = fill(
            """
            $*{setupCall}
            JS::Rooted<JS::Value> thisValJS(s.GetContext());
            if (!ToJSValue(s.GetContext(), thisVal, &thisValJS)) {
              aRv.Throw(NS_ERROR_FAILURE);
              return${errorReturn};
            }
            return ${methodName}(${callArgs});
            """,
            setupCall=setupCall,
            errorReturn=errorReturn,
            methodName=method.name,
            callArgs=", ".join(argnamesWithThis),
        )
        bodyWithoutThis = fill(
            """
            $*{setupCall}
            return ${methodName}(${callArgs});
            """,
            setupCall=setupCall,
            errorReturn=errorReturn,
            methodName=method.name,
            callArgs=", ".join(argnamesWithoutThis),
        )
        bodyWithThisWithoutRv = fill(
            """
            return ${methodName}(${callArgs});
            """,
            methodName=method.name,
            callArgs=", ".join(argnamesWithoutRv),
        )
        bodyWithoutThisAndRv = fill(
            """
            return ${methodName}(${callArgs});
            """,
            methodName=method.name,
            callArgs=", ".join(argnamesWithoutThisAndRv),
        )

        return [
            ClassMethod(
                method.name,
                method.returnType,
                args,
                bodyInHeader=True,
                templateArgs=["typename T"],
                body=bodyWithThis,
                canRunScript=method.canRunScript,
            ),
            ClassMethod(
                method.name,
                method.returnType,
                argsWithoutThis,
                bodyInHeader=True,
                body=bodyWithoutThis,
                canRunScript=method.canRunScript,
            ),
            ClassMethod(
                method.name,
                method.returnType,
                argsWithoutRv,
                bodyInHeader=True,
                templateArgs=["typename T"],
                body=bodyWithThisWithoutRv,
                canRunScript=method.canRunScript,
            ),
            ClassMethod(
                method.name,
                method.returnType,
                argsWithoutThisAndRv,
                bodyInHeader=True,
                body=bodyWithoutThisAndRv,
                canRunScript=method.canRunScript,
            ),
            method,
        ]

    def deps(self):
        return self._deps


class CGCallbackFunction(CGCallback):
    def __init__(self, callback, descriptorProvider):
        self.callback = callback
        if callback.isConstructor():
            methods = [ConstructCallback(callback, descriptorProvider)]
        else:
            methods = [CallCallback(callback, descriptorProvider)]
        CGCallback.__init__(
            self, callback, descriptorProvider, "CallbackFunction", methods
        )

    def getConstructors(self):
        return CGCallback.getConstructors(self) + [
            ClassConstructor(
                [Argument("CallbackFunction*", "aOther")],
                bodyInHeader=True,
                visibility="public",
                explicit=True,
                baseConstructors=["CallbackFunction(aOther)"],
            )
        ]


class CGFastCallback(CGClass):
    def __init__(self, idlObject):
        self._deps = idlObject.getDeps()
        baseName = idlObject.identifier.name
        constructor = ClassConstructor(
            [
                Argument("JSObject*", "aCallback"),
                Argument("JSObject*", "aCallbackGlobal"),
            ],
            bodyInHeader=True,
            visibility="public",
            explicit=True,
            baseConstructors=[
                "%s(aCallback, aCallbackGlobal, FastCallbackConstructor())" % baseName,
            ],
            body="",
        )

        traceMethod = ClassMethod(
            "Trace",
            "void",
            [Argument("JSTracer*", "aTracer")],
            inline=True,
            bodyInHeader=True,
            visibility="public",
            body="%s::Trace(aTracer);\n" % baseName,
        )
        holdMethod = ClassMethod(
            "FinishSlowJSInitIfMoreThanOneOwner",
            "void",
            [Argument("JSContext*", "aCx")],
            inline=True,
            bodyInHeader=True,
            visibility="public",
            body=("%s::FinishSlowJSInitIfMoreThanOneOwner(aCx);\n" % baseName),
        )

        CGClass.__init__(
            self,
            "Fast%s" % baseName,
            bases=[ClassBase(baseName)],
            constructors=[constructor],
            methods=[traceMethod, holdMethod],
        )

    def deps(self):
        return self._deps


class CGCallbackInterface(CGCallback):
    def __init__(self, descriptor, spiderMonkeyInterfacesAreStructs=False):
        iface = descriptor.interface
        attrs = [
            m
            for m in iface.members
            if (
                m.isAttr()
                and not m.isStatic()
                and (not m.isMaplikeOrSetlikeAttr() or not iface.isJSImplemented())
            )
        ]
        getters = [
            CallbackGetter(a, descriptor, spiderMonkeyInterfacesAreStructs)
            for a in attrs
        ]
        setters = [
            CallbackSetter(a, descriptor, spiderMonkeyInterfacesAreStructs)
            for a in attrs
            if not a.readonly
        ]
        methods = [
            m
            for m in iface.members
            if (
                m.isMethod()
                and not m.isStatic()
                and not m.isIdentifierLess()
                and (
                    not m.isMaplikeOrSetlikeOrIterableMethod()
                    or not iface.isJSImplemented()
                )
            )
        ]
        methods = [
            CallbackOperation(m, sig, descriptor, spiderMonkeyInterfacesAreStructs)
            for m in methods
            for sig in m.signatures()
        ]

        needInitId = False
        if iface.isJSImplemented() and iface.ctor():
            sigs = descriptor.interface.ctor().signatures()
            if len(sigs) != 1:
                raise TypeError("We only handle one constructor.  See bug 869268.")
            methods.append(CGJSImplInitOperation(sigs[0], descriptor))
            needInitId = True

        idlist = [
            descriptor.binaryNameFor(m.identifier.name, m.isStatic())
            for m in iface.members
            if m.isAttr() or m.isMethod()
        ]
        if needInitId:
            idlist.append("__init")

        if iface.isJSImplemented() and iface.getExtendedAttribute(
            "WantsEventListenerHooks"
        ):
            methods.append(CGJSImplEventHookOperation(descriptor, "eventListenerAdded"))
            methods.append(
                CGJSImplEventHookOperation(descriptor, "eventListenerRemoved")
            )
            idlist.append("eventListenerAdded")
            idlist.append("eventListenerRemoved")

        if len(idlist) != 0:
            methods.append(initIdsClassMethod(idlist, iface.identifier.name + "Atoms"))
        CGCallback.__init__(
            self,
            iface,
            descriptor,
            "CallbackInterface",
            methods,
            getters=getters,
            setters=setters,
        )


class FakeMember:
    def __init__(self, name=None):
        if name is not None:
            self.identifier = FakeIdentifier(name)

    def isStatic(self):
        return False

    def isAttr(self):
        return False

    def isMethod(self):
        return False

    def getExtendedAttribute(self, name):
        # Claim to be a [NewObject] so we can avoid the "return a raw pointer"
        # comments CGNativeMember codegen would otherwise stick in.
        if name == "NewObject":
            return True
        return None


class CallbackMember(CGNativeMember):
    # XXXbz It's OK to use CallbackKnownNotGray for wrapScope because
    # CallSetup already handled the unmark-gray bits for us. we don't have
    # anything better to use for 'obj', really...
    def __init__(
        self,
        sig,
        name,
        descriptorProvider,
        needThisHandling,
        rethrowContentException=False,
        spiderMonkeyInterfacesAreStructs=False,
        wrapScope=None,
        canRunScript=False,
        passJSBitsAsNeeded=False,
    ):
        """
        needThisHandling is True if we need to be able to accept a specified
        thisObj, False otherwise.
        """
        assert not rethrowContentException or not needThisHandling

        self.retvalType = sig[0]
        self.originalSig = sig
        args = sig[1]
        self.argCount = len(args)
        if self.argCount > 0:
            # Check for variadic arguments
            lastArg = args[self.argCount - 1]
            if lastArg.variadic:
                self.argCountStr = "(%d - 1) + %s.Length()" % (
                    self.argCount,
                    lastArg.identifier.name,
                )
            else:
                self.argCountStr = "%d" % self.argCount
        self.needThisHandling = needThisHandling
        # If needThisHandling, we generate ourselves as private and the caller
        # will handle generating public versions that handle the "this" stuff.
        visibility = "private" if needThisHandling else "public"
        self.rethrowContentException = rethrowContentException

        self.wrapScope = wrapScope
        # We don't care, for callback codegen, whether our original member was
        # a method or attribute or whatnot.  Just always pass FakeMember()
        # here.
        CGNativeMember.__init__(
            self,
            descriptorProvider,
            FakeMember(),
            name,
            (self.retvalType, args),
            extendedAttrs=["needsErrorResult"],
            passJSBitsAsNeeded=passJSBitsAsNeeded,
            visibility=visibility,
            spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs,
            canRunScript=canRunScript,
        )
        # We have to do all the generation of our body now, because
        # the caller relies on us throwing if we can't manage it.
        self.body = self.getImpl()

    def getImpl(self):
        setupCall = self.getCallSetup()
        declRval = self.getRvalDecl()
        if self.argCount > 0:
            argvDecl = fill(
                """
                JS::RootedVector<JS::Value> argv(cx);
                if (!argv.resize(${argCount})) {
                  $*{failureCode}
                  return${errorReturn};
                }
                """,
                argCount=self.argCountStr,
                failureCode=self.getArgvDeclFailureCode(),
                errorReturn=self.getDefaultRetval(),
            )
        else:
            # Avoid weird 0-sized arrays
            argvDecl = ""
        convertArgs = self.getArgConversions()
        doCall = self.getCall()
        returnResult = self.getResultConversion()

        body = declRval + argvDecl + convertArgs + doCall
        if self.needsScopeBody():
            body = "{\n" + indent(body) + "}\n"
        return setupCall + body + returnResult

    def needsScopeBody(self):
        return False

    def getArgvDeclFailureCode(self):
        return dedent(
            """
            // That threw an exception on the JSContext, and our CallSetup will do
            // the right thing with that.
            """
        )

    def getExceptionCode(self, forResult):
        return fill(
            """
            aRv.Throw(NS_ERROR_UNEXPECTED);
            return${defaultRetval};
            """,
            defaultRetval=self.getDefaultRetval(),
        )

    def getResultConversion(
        self, val="rval", failureCode=None, isDefinitelyObject=False, exceptionCode=None
    ):
        replacements = {
            "val": val,
            "holderName": "rvalHolder",
            "declName": "rvalDecl",
            # We actually want to pass in a null scope object here, because
            # wrapping things into our current compartment (that of mCallback)
            # is what we want.
            "obj": "nullptr",
            "passedToJSImpl": "false",
        }

        if isJSImplementedDescriptor(self.descriptorProvider):
            isCallbackReturnValue = "JSImpl"
        else:
            isCallbackReturnValue = "Callback"
        sourceDescription = "return value of %s" % self.getPrettyName()
        convertType = instantiateJSToNativeConversion(
            getJSToNativeConversionInfo(
                self.retvalType,
                self.descriptorProvider,
                failureCode=failureCode,
                isDefinitelyObject=isDefinitelyObject,
                exceptionCode=exceptionCode or self.getExceptionCode(forResult=True),
                isCallbackReturnValue=isCallbackReturnValue,
                # Allow returning a callback type that
                # allows non-callable objects.
                allowTreatNonCallableAsNull=True,
                sourceDescription=sourceDescription,
            ),
            replacements,
        )
        assignRetval = string.Template(
            self.getRetvalInfo(self.retvalType, False)[2]
        ).substitute(replacements)
        type = convertType.define()
        return type + assignRetval

    def getArgConversions(self):
        # Just reget the arglist from self.originalSig, because our superclasses
        # just have way to many members they like to clobber, so I can't find a
        # safe member name to store it in.
        argConversions = [
            self.getArgConversion(i, arg) for i, arg in enumerate(self.originalSig[1])
        ]
        if not argConversions:
            return "\n"

        # Do them back to front, so our argc modifications will work
        # correctly, because we examine trailing arguments first.
        argConversions.reverse()
        # Wrap each one in a scope so that any locals it has don't leak out, and
        # also so that we can just "break;" for our successCode.
        argConversions = [
            CGWrapper(CGIndenter(CGGeneric(c)), pre="do {\n", post="} while (false);\n")
            for c in argConversions
        ]
        if self.argCount > 0:
            argConversions.insert(0, self.getArgcDecl())
        # And slap them together.
        return CGList(argConversions, "\n").define() + "\n"

    def getArgConversion(self, i, arg):
        argval = arg.identifier.name

        if arg.variadic:
            argval = argval + "[idx]"
            jsvalIndex = "%d + idx" % i
        else:
            jsvalIndex = "%d" % i
            if arg.canHaveMissingValue():
                argval += ".Value()"

        prepend = ""

        wrapScope = self.wrapScope
        if arg.type.isUnion() and wrapScope is None:
            prepend += (
                "JS::Rooted<JSObject*> callbackObj(cx, CallbackKnownNotGray());\n"
            )
            wrapScope = "callbackObj"

        conversion = prepend + wrapForType(
            arg.type,
            self.descriptorProvider,
            {
                "result": argval,
                "successCode": "continue;\n" if arg.variadic else "break;\n",
                "jsvalRef": "argv[%s]" % jsvalIndex,
                "jsvalHandle": "argv[%s]" % jsvalIndex,
                "obj": wrapScope,
                "returnsNewObject": False,
                "exceptionCode": self.getExceptionCode(forResult=False),
                "spiderMonkeyInterfacesAreStructs": self.spiderMonkeyInterfacesAreStructs,
            },
        )

        if arg.variadic:
            conversion = fill(
                """
                for (uint32_t idx = 0; idx < ${arg}.Length(); ++idx) {
                  $*{conversion}
                }
                break;
                """,
                arg=arg.identifier.name,
                conversion=conversion,
            )
        elif arg.canHaveMissingValue():
            conversion = fill(
                """
                if (${argName}.WasPassed()) {
                  $*{conversion}
                } else if (argc == ${iPlus1}) {
                  // This is our current trailing argument; reduce argc
                  --argc;
                } else {
                  argv[${i}].setUndefined();
                }
                """,
                argName=arg.identifier.name,
                conversion=conversion,
                iPlus1=i + 1,
                i=i,
            )
        return conversion

    def getDefaultRetval(self):
        default = self.getRetvalInfo(self.retvalType, False)[1]
        if len(default) != 0:
            default = " " + default
        return default

    def getArgs(self, returnType, argList):
        args = CGNativeMember.getArgs(self, returnType, argList)
        if not self.needThisHandling:
            # Since we don't need this handling, we're the actual method that
            # will be called, so we need an aRethrowExceptions argument.
            if not self.rethrowContentException:
                args.append(Argument("const char*", "aExecutionReason", "nullptr"))
                args.append(
                    Argument(
                        "ExceptionHandling", "aExceptionHandling", "eReportExceptions"
                    )
                )
            args.append(Argument("JS::Realm*", "aRealm", "nullptr"))
            return args
        # We want to allow the caller to pass in a "this" value, as
        # well as a BindingCallContext.
        return [
            Argument("BindingCallContext&", "cx"),
            Argument("JS::Handle<JS::Value>", "aThisVal"),
        ] + args

    def getCallSetup(self):
        if self.needThisHandling:
            # It's been done for us already
            return ""
        callSetup = "CallSetup s(this, aRv"
        if self.rethrowContentException:
            # getArgs doesn't add the aExceptionHandling argument but does add
            # aRealm for us.
            callSetup += (
                ', "%s", eRethrowContentExceptions, aRealm, /* aIsJSImplementedWebIDL = */ '
                % self.getPrettyName()
            )
            callSetup += toStringBool(
                isJSImplementedDescriptor(self.descriptorProvider)
            )
        else:
            callSetup += ', "%s", aExceptionHandling, aRealm' % self.getPrettyName()
        callSetup += ");\n"
        return fill(
            """
            $*{callSetup}
            if (aRv.Failed()) {
              return${errorReturn};
            }
            MOZ_ASSERT(s.GetContext());
            BindingCallContext& cx = s.GetCallContext();

            """,
            callSetup=callSetup,
            errorReturn=self.getDefaultRetval(),
        )

    def getArgcDecl(self):
        return CGGeneric("unsigned argc = %s;\n" % self.argCountStr)

    @staticmethod
    def ensureASCIIName(idlObject):
        type = "attribute" if idlObject.isAttr() else "operation"
        if re.match("[^\x20-\x7E]", idlObject.identifier.name):
            raise SyntaxError(
                'Callback %s name "%s" contains non-ASCII '
                "characters.  We can't handle that.  %s"
                % (type, idlObject.identifier.name, idlObject.location)
            )
        if re.match('"', idlObject.identifier.name):
            raise SyntaxError(
                "Callback %s name '%s' contains "
                "double-quote character.  We can't handle "
                "that.  %s" % (type, idlObject.identifier.name, idlObject.location)
            )


class ConstructCallback(CallbackMember):
    def __init__(self, callback, descriptorProvider):
        self.callback = callback
        CallbackMember.__init__(
            self,
            callback.signatures()[0],
            "Construct",
            descriptorProvider,
            needThisHandling=False,
            canRunScript=True,
        )

    def getRvalDecl(self):
        # Box constructedObj for getJSToNativeConversionInfo().
        return "JS::Rooted<JS::Value> rval(cx);\n"

    def getCall(self):
        if self.argCount > 0:
            args = "JS::HandleValueArray::subarray(argv, 0, argc)"
        else:
            args = "JS::HandleValueArray::empty()"

        return fill(
            """
            JS::Rooted<JS::Value> constructor(cx, JS::ObjectValue(*mCallback));
            JS::Rooted<JSObject*> constructedObj(cx);
            if (!JS::Construct(cx, constructor,
                          ${args}, &constructedObj)) {
              aRv.NoteJSContextException(cx);
              return${errorReturn};
            }
            rval.setObject(*constructedObj);
            """,
            args=args,
            errorReturn=self.getDefaultRetval(),
        )

    def getResultConversion(self):
        return CallbackMember.getResultConversion(self, isDefinitelyObject=True)

    def getPrettyName(self):
        return self.callback.identifier.name


class CallbackMethod(CallbackMember):
    def __init__(
        self,
        sig,
        name,
        descriptorProvider,
        needThisHandling,
        rethrowContentException=False,
        spiderMonkeyInterfacesAreStructs=False,
        canRunScript=False,
    ):
        CallbackMember.__init__(
            self,
            sig,
            name,
            descriptorProvider,
            needThisHandling,
            rethrowContentException,
            spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs,
            canRunScript=canRunScript,
        )

    def getRvalDecl(self):
        return "JS::Rooted<JS::Value> rval(cx);\n"

    def getNoteCallFailed(self):
        return fill(
            """
                aRv.NoteJSContextException(cx);
                return${errorReturn};
                """,
            errorReturn=self.getDefaultRetval(),
        )

    def getCall(self):
        if self.argCount > 0:
            args = "JS::HandleValueArray::subarray(argv, 0, argc)"
        else:
            args = "JS::HandleValueArray::empty()"

        return fill(
            """
            $*{declCallable}
            $*{declThis}
            if (${callGuard}!JS::Call(cx, ${thisVal}, callable,
                          ${args}, &rval)) {
              $*{noteError}
            }
            """,
            declCallable=self.getCallableDecl(),
            declThis=self.getThisDecl(),
            callGuard=self.getCallGuard(),
            thisVal=self.getThisVal(),
            args=args,
            noteError=self.getNoteCallFailed(),
        )


class CallCallback(CallbackMethod):
    def __init__(self, callback, descriptorProvider):
        self.callback = callback
        CallbackMethod.__init__(
            self,
            callback.signatures()[0],
            "Call",
            descriptorProvider,
            needThisHandling=True,
            canRunScript=not callback.isRunScriptBoundary(),
        )

    def getNoteCallFailed(self):
        if self.retvalType.isPromise():
            return dedent(
                """
                // Convert exception to a rejected promise.
                // See https://heycam.github.io/webidl/#call-a-user-objects-operation
                // step 12 and step 15.5.
                return CreateRejectedPromiseFromThrownException(cx, aRv);
                """
            )
        return CallbackMethod.getNoteCallFailed(self)

    def getExceptionCode(self, forResult):
        # If the result value is a promise, and conversion
        # to the promise throws an exception we shouldn't
        # try to convert that exception to a promise again.
        if self.retvalType.isPromise() and not forResult:
            return dedent(
                """
                // Convert exception to a rejected promise.
                // See https://heycam.github.io/webidl/#call-a-user-objects-operation
                // step 10 and step 15.5.
                return CreateRejectedPromiseFromThrownException(cx, aRv);
                """
            )
        return CallbackMethod.getExceptionCode(self, forResult)

    def getThisDecl(self):
        return ""

    def getThisVal(self):
        return "aThisVal"

    def getCallableDecl(self):
        return "JS::Rooted<JS::Value> callable(cx, JS::ObjectValue(*mCallback));\n"

    def getPrettyName(self):
        return self.callback.identifier.name

    def getCallGuard(self):
        if self.callback._treatNonObjectAsNull:
            return "JS::IsCallable(mCallback) && "
        return ""


class CallbackOperationBase(CallbackMethod):
    """
    Common class for implementing various callback operations.
    """

    def __init__(
        self,
        signature,
        jsName,
        nativeName,
        descriptor,
        singleOperation,
        rethrowContentException=False,
        spiderMonkeyInterfacesAreStructs=False,
    ):
        self.singleOperation = singleOperation
        self.methodName = descriptor.binaryNameFor(jsName, False)
        CallbackMethod.__init__(
            self,
            signature,
            nativeName,
            descriptor,
            singleOperation,
            rethrowContentException,
            spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs,
        )

    def getThisDecl(self):
        if not self.singleOperation:
            return "JS::Rooted<JS::Value> thisValue(cx, JS::ObjectValue(*mCallback));\n"
        # This relies on getCallableDecl declaring a boolean
        # isCallable in the case when we're a single-operation
        # interface.
        return dedent(
            """
            JS::Rooted<JS::Value> thisValue(cx, isCallable ? aThisVal.get()
                                                           : JS::ObjectValue(*mCallback));
            """
        )

    def getThisVal(self):
        return "thisValue"

    def getCallableDecl(self):
        getCallableFromProp = fill(
            """
            ${atomCacheName}* atomsCache = GetAtomCache<${atomCacheName}>(cx);
            if ((reinterpret_cast<jsid*>(atomsCache)->isVoid() &&
                 !InitIds(cx, atomsCache)) ||
                !GetCallableProperty(cx, atomsCache->${methodAtomName}, &callable)) {
              aRv.Throw(NS_ERROR_UNEXPECTED);
              return${errorReturn};
            }
            """,
            methodAtomName=CGDictionary.makeIdName(self.methodName),
            atomCacheName=self.descriptorProvider.interface.identifier.name + "Atoms",
            errorReturn=self.getDefaultRetval(),
        )
        if not self.singleOperation:
            return "JS::Rooted<JS::Value> callable(cx);\n" + getCallableFromProp
        return fill(
            """
            bool isCallable = JS::IsCallable(mCallback);
            JS::Rooted<JS::Value> callable(cx);
            if (isCallable) {
              callable = JS::ObjectValue(*mCallback);
            } else {
              $*{getCallableFromProp}
            }
            """,
            getCallableFromProp=getCallableFromProp,
        )

    def getCallGuard(self):
        return ""


class CallbackOperation(CallbackOperationBase):
    """
    Codegen actual WebIDL operations on callback interfaces.
    """

    def __init__(self, method, signature, descriptor, spiderMonkeyInterfacesAreStructs):
        self.ensureASCIIName(method)
        self.method = method
        jsName = method.identifier.name
        CallbackOperationBase.__init__(
            self,
            signature,
            jsName,
            MakeNativeName(descriptor.binaryNameFor(jsName, False)),
            descriptor,
            descriptor.interface.isSingleOperationInterface(),
            rethrowContentException=descriptor.interface.isJSImplemented(),
            spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs,
        )

    def getPrettyName(self):
        return "%s.%s" % (
            self.descriptorProvider.interface.identifier.name,
            self.method.identifier.name,
        )


class CallbackAccessor(CallbackMember):
    """
    Shared superclass for CallbackGetter and CallbackSetter.
    """

    def __init__(self, attr, sig, name, descriptor, spiderMonkeyInterfacesAreStructs):
        self.ensureASCIIName(attr)
        self.attrName = attr.identifier.name
        CallbackMember.__init__(
            self,
            sig,
            name,
            descriptor,
            needThisHandling=False,
            rethrowContentException=descriptor.interface.isJSImplemented(),
            spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs,
        )

    def getPrettyName(self):
        return "%s.%s" % (
            self.descriptorProvider.interface.identifier.name,
            self.attrName,
        )


class CallbackGetter(CallbackAccessor):
    def __init__(self, attr, descriptor, spiderMonkeyInterfacesAreStructs):
        CallbackAccessor.__init__(
            self,
            attr,
            (attr.type, []),
            callbackGetterName(attr, descriptor),
            descriptor,
            spiderMonkeyInterfacesAreStructs,
        )

    def getRvalDecl(self):
        return "JS::Rooted<JS::Value> rval(cx);\n"

    def getCall(self):
        return fill(
            """
            JS::Rooted<JSObject *> callback(cx, mCallback);
            ${atomCacheName}* atomsCache = GetAtomCache<${atomCacheName}>(cx);
            if ((reinterpret_cast<jsid*>(atomsCache)->isVoid()
                 && !InitIds(cx, atomsCache)) ||
                !JS_GetPropertyById(cx, callback, atomsCache->${attrAtomName}, &rval)) {
              aRv.Throw(NS_ERROR_UNEXPECTED);
              return${errorReturn};
            }
            """,
            atomCacheName=self.descriptorProvider.interface.identifier.name + "Atoms",
            attrAtomName=CGDictionary.makeIdName(
                self.descriptorProvider.binaryNameFor(self.attrName, False)
            ),
            errorReturn=self.getDefaultRetval(),
        )


class CallbackSetter(CallbackAccessor):
    def __init__(self, attr, descriptor, spiderMonkeyInterfacesAreStructs):
        CallbackAccessor.__init__(
            self,
            attr,
            (
                BuiltinTypes[IDLBuiltinType.Types.undefined],
                [FakeArgument(attr.type)],
            ),
            callbackSetterName(attr, descriptor),
            descriptor,
            spiderMonkeyInterfacesAreStructs,
        )

    def getRvalDecl(self):
        # We don't need an rval
        return ""

    def getCall(self):
        return fill(
            """
            MOZ_ASSERT(argv.length() == 1);
            JS::Rooted<JSObject*> callback(cx, CallbackKnownNotGray());
            ${atomCacheName}* atomsCache = GetAtomCache<${atomCacheName}>(cx);
            if ((reinterpret_cast<jsid*>(atomsCache)->isVoid() &&
                 !InitIds(cx, atomsCache)) ||
                !JS_SetPropertyById(cx, callback, atomsCache->${attrAtomName}, argv[0])) {
              aRv.Throw(NS_ERROR_UNEXPECTED);
              return${errorReturn};
            }
            """,
            atomCacheName=self.descriptorProvider.interface.identifier.name + "Atoms",
            attrAtomName=CGDictionary.makeIdName(
                self.descriptorProvider.binaryNameFor(self.attrName, False)
            ),
            errorReturn=self.getDefaultRetval(),
        )

    def getArgcDecl(self):
        return None


class CGJSImplInitOperation(CallbackOperationBase):
    """
    Codegen the __Init() method used to pass along constructor arguments for JS-implemented WebIDL.
    """

    def __init__(self, sig, descriptor):
        assert sig in descriptor.interface.ctor().signatures()
        CallbackOperationBase.__init__(
            self,
            (BuiltinTypes[IDLBuiltinType.Types.undefined], sig[1]),
            "__init",
            "__Init",
            descriptor,
            singleOperation=False,
            rethrowContentException=True,
            spiderMonkeyInterfacesAreStructs=True,
        )

    def getPrettyName(self):
        return "__init"


class CGJSImplEventHookOperation(CallbackOperationBase):
    """
    Codegen the hooks on a JS impl for adding/removing event listeners.
    """

    def __init__(self, descriptor, name):
        self.name = name

        CallbackOperationBase.__init__(
            self,
            (
                BuiltinTypes[IDLBuiltinType.Types.undefined],
                [FakeArgument(BuiltinTypes[IDLBuiltinType.Types.domstring], "aType")],
            ),
            name,
            MakeNativeName(name),
            descriptor,
            singleOperation=False,
            rethrowContentException=False,
            spiderMonkeyInterfacesAreStructs=True,
        )

    def getPrettyName(self):
        return self.name


def getMaplikeOrSetlikeErrorReturn(helperImpl):
    """
    Generate return values based on whether a maplike or setlike generated
    method is an interface method (which returns bool) or a helper function
    (which uses ErrorResult).
    """
    if helperImpl:
        return dedent(
            """
            aRv.Throw(NS_ERROR_UNEXPECTED);
            return%s;
            """
            % helperImpl.getDefaultRetval()
        )
    return "return false;\n"


def getMaplikeOrSetlikeBackingObject(descriptor, maplikeOrSetlike, helperImpl=None):
    """
    Generate code to get/create a JS backing object for a maplike/setlike
    declaration from the declaration slot.
    """
    func_prefix = maplikeOrSetlike.maplikeOrSetlikeOrIterableType.title()
    ret = fill(
        """
        JS::Rooted<JSObject*> backingObj(cx);
        bool created = false;
        if (!Get${func_prefix}BackingObject(cx, obj, ${slot}, &backingObj, &created)) {
          $*{errorReturn}
        }
        if (created) {
          PreserveWrapper<${selfType}>(self);
        }
        """,
        slot=memberReservedSlot(maplikeOrSetlike, descriptor),
        func_prefix=func_prefix,
        errorReturn=getMaplikeOrSetlikeErrorReturn(helperImpl),
        selfType=descriptor.nativeType,
    )
    return ret


def getMaplikeOrSetlikeSizeGetterBody(descriptor, attr):
    """
    Creates the body for the size getter method of maplike/setlike interfaces.
    """
    # We should only have one declaration attribute currently
    assert attr.identifier.name == "size"
    assert attr.isMaplikeOrSetlikeAttr()
    return fill(
        """
        $*{getBackingObj}
        uint32_t result = JS::${funcPrefix}Size(cx, backingObj);
        MOZ_ASSERT(!JS_IsExceptionPending(cx));
        args.rval().setNumber(result);
        return true;
        """,
        getBackingObj=getMaplikeOrSetlikeBackingObject(
            descriptor, attr.maplikeOrSetlike
        ),
        funcPrefix=attr.maplikeOrSetlike.prefix,
    )


class CGMaplikeOrSetlikeMethodGenerator(CGThing):
    """
    Creates methods for maplike/setlike interfaces. It is expected that all
    methods will be have a maplike/setlike object attached. Unwrapping/wrapping
    will be taken care of by the usual method generation machinery in
    CGMethodCall/CGPerSignatureCall. Functionality is filled in here instead of
    using CGCallGenerator.
    """

    def __init__(
        self,
        descriptor,
        maplikeOrSetlike,
        methodName,
        needsValueTypeReturn=False,
        helperImpl=None,
    ):
        CGThing.__init__(self)
        # True if this will be the body of a C++ helper function.
        self.helperImpl = helperImpl
        self.descriptor = descriptor
        self.maplikeOrSetlike = maplikeOrSetlike
        self.cgRoot = CGList([])
        impl_method_name = methodName
        if impl_method_name[0] == "_":
            # double underscore means this is a js-implemented chrome only rw
            # function. Truncate the double underscore so calling the right
            # underlying JSAPI function still works.
            impl_method_name = impl_method_name[2:]
        self.cgRoot.append(
            CGGeneric(
                getMaplikeOrSetlikeBackingObject(
                    self.descriptor, self.maplikeOrSetlike, self.helperImpl
                )
            )
        )
        self.returnStmt = getMaplikeOrSetlikeErrorReturn(self.helperImpl)

        # Generates required code for the method. Method descriptions included
        # in definitions below. Throw if we don't have a method to fill in what
        # we're looking for.
        try:
            methodGenerator = getattr(self, impl_method_name)
        except AttributeError:
            raise TypeError(
                "Missing %s method definition '%s'"
                % (self.maplikeOrSetlike.maplikeOrSetlikeType, methodName)
            )
        # Method generator returns tuple, containing:
        #
        # - a list of CGThings representing setup code for preparing to call
        #   the JS API function
        # - a list of arguments needed for the JS API function we're calling
        # - list of code CGThings needed for return value conversion.
        (setupCode, arguments, setResult) = methodGenerator()

        # Create the actual method call, and then wrap it with the code to
        # return the value if needed.
        funcName = self.maplikeOrSetlike.prefix + MakeNativeName(impl_method_name)
        # Append the list of setup code CGThings
        self.cgRoot.append(CGList(setupCode))
        # Create the JS API call
        code = dedent(
            """
            if (!JS::${funcName}(${args})) {
              $*{errorReturn}
            }
            """
        )

        if needsValueTypeReturn:
            assert self.helperImpl and impl_method_name == "get"
            code += fill(
                """
                if (result.isUndefined()) {
                  aRv.Throw(NS_ERROR_NOT_AVAILABLE);
                  return${retval};
                }
                """,
                retval=self.helperImpl.getDefaultRetval(),
            )

        self.cgRoot.append(
            CGWrapper(
                CGGeneric(
                    fill(
                        code,
                        funcName=funcName,
                        args=", ".join(["cx", "backingObj"] + arguments),
                        errorReturn=self.returnStmt,
                    )
                )
            )
        )
        # Append result conversion
        self.cgRoot.append(CGList(setResult))

    def mergeTuples(self, a, b):
        """
        Expecting to take 2 tuples were all elements are lists, append the lists in
        the second tuple to the lists in the first.
        """
        return tuple([x + y for x, y in zip(a, b)])

    def appendArgConversion(self, name):
        """
        Generate code to convert arguments to JS::Values, so they can be
        passed into JSAPI functions.
        """
        return CGGeneric(
            fill(
                """
            JS::Rooted<JS::Value> ${name}Val(cx);
            if (!ToJSValue(cx, ${name}, &${name}Val)) {
              $*{errorReturn}
            }
            """,
                name=name,
                errorReturn=self.returnStmt,
            )
        )

    def appendKeyArgConversion(self):
        """
        Generates the key argument for methods. Helper functions will use
        a RootedVector<JS::Value>, while interface methods have separate JS::Values.
        """
        if self.helperImpl:
            return ([], ["argv[0]"], [])
        return ([self.appendArgConversion("arg0")], ["arg0Val"], [])

    def appendKeyAndValueArgConversion(self):
        """
        Generates arguments for methods that require a key and value. Helper
        functions will use a RootedVector<JS::Value>, while interface methods have
        separate JS::Values.
        """
        r = self.appendKeyArgConversion()
        if self.helperImpl:
            return self.mergeTuples(r, ([], ["argv[1]"], []))
        return self.mergeTuples(
            r, ([self.appendArgConversion("arg1")], ["arg1Val"], [])
        )

    def appendIteratorResult(self):
        """
        Generate code to output JSObject* return values, needed for functions that
        return iterators. Iterators cannot currently be wrapped via Xrays. If
        something that would return an iterator is called via Xray, fail early.
        """
        # TODO: Bug 1173651 - Remove check once bug 1023984 is fixed.
        code = CGGeneric(
            dedent(
                """
            // TODO (Bug 1173651): Xrays currently cannot wrap iterators. Change
            // after bug 1023984 is fixed.
            if (xpc::WrapperFactory::IsXrayWrapper(obj)) {
              JS_ReportErrorASCII(cx, "Xray wrapping of iterators not supported.");
              return false;
            }
            JS::Rooted<JSObject*> result(cx);
            JS::Rooted<JS::Value> v(cx);
            """
            )
        )
        arguments = "&v"
        setResult = CGGeneric(
            dedent(
                """
            result = &v.toObject();
            """
            )
        )
        return ([code], [arguments], [setResult])

    def appendSelfResult(self):
        """
        Generate code to return the interface object itself.
        """
        code = CGGeneric(
            dedent(
                """
            JS::Rooted<JSObject*> result(cx);
            """
            )
        )
        setResult = CGGeneric(
            dedent(
                """
            result = obj;
            """
            )
        )
        return ([code], [], [setResult])

    def appendBoolResult(self):
        if self.helperImpl:
            return ([CGGeneric("bool retVal;\n")], ["&retVal"], [])
        return ([CGGeneric("bool result;\n")], ["&result"], [])

    def forEach(self):
        """
        void forEach(callback c, any thisval);

        ForEach takes a callback, and a possible value to use as 'this'. The
        callback needs to take value, key, and the interface object
        implementing maplike/setlike. In order to make sure that the third arg
        is our interface object instead of the map/set backing object, we
        create a js function with the callback and original object in its
        storage slots, then use a helper function in BindingUtils to make sure
        the callback is called correctly.
        """
        assert not self.helperImpl
        code = [
            CGGeneric(
                dedent(
                    """
            // Create a wrapper function.
            JSFunction* func = js::NewFunctionWithReserved(cx, ForEachHandler, 3, 0, nullptr);
            if (!func) {
              return false;
            }
            JS::Rooted<JSObject*> funcObj(cx, JS_GetFunctionObject(func));
            JS::Rooted<JS::Value> funcVal(cx, JS::ObjectValue(*funcObj));
            js::SetFunctionNativeReserved(funcObj, FOREACH_CALLBACK_SLOT,
                                          JS::ObjectValue(*arg0));
            js::SetFunctionNativeReserved(funcObj, FOREACH_MAPLIKEORSETLIKEOBJ_SLOT,
                                          JS::ObjectValue(*obj));
            """
                )
            )
        ]
        arguments = ["funcVal", "arg1"]
        return (code, arguments, [])

    def set(self):
        """
        object set(key, value);

        Maplike only function, takes key and sets value to it, returns
        interface object unless being called from a C++ helper.
        """
        assert self.maplikeOrSetlike.isMaplike()
        r = self.appendKeyAndValueArgConversion()
        if self.helperImpl:
            return r
        return self.mergeTuples(r, self.appendSelfResult())

    def add(self):
        """
        object add(value);

        Setlike only function, adds value to set, returns interface object
        unless being called from a C++ helper
        """
        assert self.maplikeOrSetlike.isSetlike()
        r = self.appendKeyArgConversion()
        if self.helperImpl:
            return r
        return self.mergeTuples(r, self.appendSelfResult())

    def get(self):
        """
        type? get(key);

        Retrieves a value from a backing object based on the key. Returns value
        if key is in backing object, undefined otherwise.
        """
        assert self.maplikeOrSetlike.isMaplike()
        r = self.appendKeyArgConversion()

        code = []
        # We don't need to create the result variable because it'll be created elsewhere
        # for JSObject Get method
        if not self.helperImpl or not self.helperImpl.needsScopeBody():
            code = [
                CGGeneric(
                    dedent(
                        """
                        JS::Rooted<JS::Value> result(cx);
                        """
                    )
                )
            ]

        arguments = ["&result"]
        return self.mergeTuples(r, (code, arguments, []))

    def has(self):
        """
        bool has(key);

        Check if an entry exists in the backing object. Returns true if value
        exists in backing object, false otherwise.
        """
        return self.mergeTuples(self.appendKeyArgConversion(), self.appendBoolResult())

    def keys(self):
        """
        object keys();

        Returns new object iterator with all keys from backing object.
        """
        return self.appendIteratorResult()

    def values(self):
        """
        object values();

        Returns new object iterator with all values from backing object.
        """
        return self.appendIteratorResult()

    def entries(self):
        """
        object entries();

        Returns new object iterator with all keys and values from backing
        object. Keys will be null for set.
        """
        return self.appendIteratorResult()

    def clear(self):
        """
        void clear();

        Removes all entries from map/set.
        """
        return ([], [], [])

    def delete(self):
        """
        bool delete(key);

        Deletes an entry from the backing object. Returns true if value existed
        in backing object, false otherwise.
        """
        return self.mergeTuples(self.appendKeyArgConversion(), self.appendBoolResult())

    def define(self):
        return self.cgRoot.define()


class CGHelperFunctionGenerator(CallbackMember):
    """
    Generates code to allow C++ to perform operations. Gets a context from the
    binding wrapper, turns arguments into JS::Values (via
    CallbackMember/CGNativeMember argument conversion), then uses
    getCall to generate the body for getting result, and maybe convert the
    result into return type (via CallbackMember/CGNativeMember result
    conversion)
    """

    class HelperFunction(CGAbstractMethod):
        """
        Generates context retrieval code and rooted JSObject for interface for
        method generator to use
        """

        def __init__(self, descriptor, name, args, code, returnType):
            self.code = code
            CGAbstractMethod.__init__(self, descriptor, name, returnType, args)

        def definition_body(self):
            return self.code

    def __init__(
        self,
        descriptor,
        name,
        args,
        returnType=BuiltinTypes[IDLBuiltinType.Types.undefined],
        needsResultConversion=True,
    ):
        assert returnType.isType()
        self.needsResultConversion = needsResultConversion

        # Run CallbackMember init function to generate argument conversion code.
        # wrapScope is set to 'obj' when generating maplike or setlike helper
        # functions, as we don't have access to the CallbackPreserveColor
        # method.
        CallbackMember.__init__(
            self,
            [returnType, args],
            name,
            descriptor,
            False,
            wrapScope="obj",
            passJSBitsAsNeeded=typeNeedsCx(returnType),
        )

        # Wrap CallbackMember body code into a CGAbstractMethod to make
        # generation easier.
        self.implMethod = CGHelperFunctionGenerator.HelperFunction(
            descriptor, name, self.args, self.body, self.returnType
        )

    def getCallSetup(self):
        # If passJSBitsAsNeeded is true, it means the caller will provide a
        # JSContext, so we don't need to create JSContext and enter
        # UnprivilegedJunkScopeOrWorkerGlobal here.
        code = "MOZ_ASSERT(self);\n"
        if not self.passJSBitsAsNeeded:
            code += dedent(
                """
                AutoJSAPI jsapi;
                jsapi.Init();
                JSContext* cx = jsapi.cx();
                // It's safe to use UnprivilegedJunkScopeOrWorkerGlobal here because
                // all we want is to wrap into _some_ scope and then unwrap to find
                // the reflector, and wrapping has no side-effects.
                JSObject* scope = UnprivilegedJunkScopeOrWorkerGlobal(fallible);
                if (!scope) {
                  aRv.Throw(NS_ERROR_UNEXPECTED);
                  return%s;
                }
                JSAutoRealm tempRealm(cx, scope);
                """
                % self.getDefaultRetval()
            )

        code += dedent(
            """
            JS::Rooted<JS::Value> v(cx);
            if(!ToJSValue(cx, self, &v)) {
              aRv.Throw(NS_ERROR_UNEXPECTED);
              return%s;
            }
            // This is a reflector, but due to trying to name things
            // similarly across method generators, it's called obj here.
            JS::Rooted<JSObject*> obj(cx);
            obj = js::UncheckedUnwrap(&v.toObject(), /* stopAtWindowProxy = */ false);
            """
            % self.getDefaultRetval()
        )

        # We'd like wrap the inner code in a scope such that the code can use the
        # same realm. So here we are creating the result variable outside of the
        # scope.
        if self.needsScopeBody():
            code += "JS::Rooted<JS::Value> result(cx);\n"

        return code

    def getArgs(self, returnType, argList):
        # We don't need the context or the value. We'll generate those instead.
        args = CGNativeMember.getArgs(self, returnType, argList)
        # Prepend a pointer to the binding object onto the arguments
        return [Argument(self.descriptorProvider.nativeType + "*", "self")] + args

    def needsScopeBody(self):
        return self.passJSBitsAsNeeded

    def getArgvDeclFailureCode(self):
        return "aRv.Throw(NS_ERROR_UNEXPECTED);\n"

    def getResultConversion(self):
        if self.needsResultConversion:
            code = ""
            if self.needsScopeBody():
                code = dedent(
                    """
                    if (!JS_WrapValue(cx, &result)) {
                      aRv.NoteJSContextException(cx);
                      return;
                    }
                    """
                )

            failureCode = dedent("aRv.Throw(NS_ERROR_UNEXPECTED);\nreturn nullptr;\n")

            exceptionCode = None
            if self.retvalType.isPrimitive():
                exceptionCode = dedent(
                    "aRv.NoteJSContextException(cx);\nreturn%s;\n"
                    % self.getDefaultRetval()
                )

            return code + CallbackMember.getResultConversion(
                self,
                "result",
                failureCode=failureCode,
                isDefinitelyObject=True,
                exceptionCode=exceptionCode,
            )

        assignRetval = string.Template(
            self.getRetvalInfo(self.retvalType, False)[2]
        ).substitute(
            {
                "declName": "retVal",
            }
        )
        return assignRetval

    def getRvalDecl(self):
        # hack to make sure we put JSAutoRealm inside the body scope
        return "JSAutoRealm reflectorRealm(cx, obj);\n"

    def getArgcDecl(self):
        # Don't need argc for anything.
        return None

    def getCall(self):
        assert False  # Override me!

    def getPrettyName(self):
        return self.name

    def declare(self):
        return self.implMethod.declare()

    def define(self):
        return self.implMethod.define()


class CGMaplikeOrSetlikeHelperFunctionGenerator(CGHelperFunctionGenerator):
    """
    Generates code to allow C++ to perform operations on backing objects. Gets
    a context from the binding wrapper, turns arguments into JS::Values (via
    CallbackMember/CGNativeMember argument conversion), then uses
    CGMaplikeOrSetlikeMethodGenerator to generate the body.
    """

    def __init__(
        self,
        descriptor,
        maplikeOrSetlike,
        name,
        needsKeyArg=False,
        needsValueArg=False,
        needsValueTypeReturn=False,
        needsBoolReturn=False,
        needsResultConversion=True,
    ):
        self.maplikeOrSetlike = maplikeOrSetlike
        self.needsValueTypeReturn = needsValueTypeReturn

        args = []
        if needsKeyArg:
            args.append(FakeArgument(maplikeOrSetlike.keyType, "aKey"))
        if needsValueArg:
            assert needsKeyArg
            assert not needsValueTypeReturn
            args.append(FakeArgument(maplikeOrSetlike.valueType, "aValue"))

        returnType = BuiltinTypes[IDLBuiltinType.Types.undefined]
        if needsBoolReturn:
            returnType = BuiltinTypes[IDLBuiltinType.Types.boolean]
        elif needsValueTypeReturn:
            returnType = maplikeOrSetlike.valueType

        CGHelperFunctionGenerator.__init__(
            self,
            descriptor,
            name,
            args,
            returnType,
            needsResultConversion,
        )

    def getCall(self):
        return CGMaplikeOrSetlikeMethodGenerator(
            self.descriptorProvider,
            self.maplikeOrSetlike,
            self.name.lower(),
            self.needsValueTypeReturn,
            helperImpl=self,
        ).define()


class CGMaplikeOrSetlikeHelperGenerator(CGNamespace):
    """
    Declares and defines convenience methods for accessing backing objects on
    setlike/maplike interface. Generates function signatures, un/packs
    backing objects from slot, etc.
    """

    def __init__(self, descriptor, maplikeOrSetlike):
        self.descriptor = descriptor
        # Since iterables are folded in with maplike/setlike, make sure we've
        # got the right type here.
        assert maplikeOrSetlike.isMaplike() or maplikeOrSetlike.isSetlike()
        self.maplikeOrSetlike = maplikeOrSetlike
        self.namespace = "%sHelpers" % (
            self.maplikeOrSetlike.maplikeOrSetlikeOrIterableType.title()
        )
        self.helpers = [
            CGMaplikeOrSetlikeHelperFunctionGenerator(
                descriptor, maplikeOrSetlike, "Clear"
            ),
            CGMaplikeOrSetlikeHelperFunctionGenerator(
                descriptor,
                maplikeOrSetlike,
                "Delete",
                needsKeyArg=True,
                needsBoolReturn=True,
                needsResultConversion=False,
            ),
            CGMaplikeOrSetlikeHelperFunctionGenerator(
                descriptor,
                maplikeOrSetlike,
                "Has",
                needsKeyArg=True,
                needsBoolReturn=True,
                needsResultConversion=False,
            ),
        ]
        if self.maplikeOrSetlike.isMaplike():
            self.helpers.append(
                CGMaplikeOrSetlikeHelperFunctionGenerator(
                    descriptor,
                    maplikeOrSetlike,
                    "Set",
                    needsKeyArg=True,
                    needsValueArg=True,
                )
            )
            self.helpers.append(
                CGMaplikeOrSetlikeHelperFunctionGenerator(
                    descriptor,
                    maplikeOrSetlike,
                    "Get",
                    needsKeyArg=True,
                    needsValueTypeReturn=True,
                )
            )
        else:
            assert self.maplikeOrSetlike.isSetlike()
            self.helpers.append(
                CGMaplikeOrSetlikeHelperFunctionGenerator(
                    descriptor, maplikeOrSetlike, "Add", needsKeyArg=True
                )
            )
        CGNamespace.__init__(self, self.namespace, CGList(self.helpers))


class CGIterableMethodGenerator(CGGeneric):
    """
    Creates methods for iterable interfaces. Unwrapping/wrapping
    will be taken care of by the usual method generation machinery in
    CGMethodCall/CGPerSignatureCall. Functionality is filled in here instead of
    using CGCallGenerator.
    """

    def __init__(self, descriptor, methodName, args):
        if methodName == "forEach":
            assert len(args) == 2

            CGGeneric.__init__(
                self,
                fill(
                    """
                if (!JS::IsCallable(arg0)) {
                  cx.ThrowErrorMessage<MSG_NOT_CALLABLE>("Argument 1");
                  return false;
                }
                JS::RootedValueArray<3> callArgs(cx);
                callArgs[2].setObject(*obj);
                JS::Rooted<JS::Value> ignoredReturnVal(cx);
                auto GetKeyAtIndex = &${selfType}::GetKeyAtIndex;
                auto GetValueAtIndex = &${selfType}::GetValueAtIndex;
                for (size_t i = 0; i < self->GetIterableLength(); ++i) {
                  if (!CallIterableGetter(cx, GetValueAtIndex, self, i,
                                          callArgs[0])) {
                    return false;
                  }
                  if (!CallIterableGetter(cx, GetKeyAtIndex, self, i,
                                          callArgs[1])) {
                    return false;
                  }
                  if (!JS::Call(cx, arg1, arg0, JS::HandleValueArray(callArgs),
                                &ignoredReturnVal)) {
                    return false;
                  }
                }
                """,
                    ifaceName=descriptor.interface.identifier.name,
                    selfType=descriptor.nativeType,
                ),
            )
            return

        if descriptor.interface.isIterable():
            assert descriptor.interface.maplikeOrSetlikeOrIterable.isPairIterator()
            assert len(args) == 0

            wrap = f"{descriptor.interface.identifier.name}Iterator_Binding::Wrap"
            iterClass = f"mozilla::dom::binding_detail::WrappableIterableIterator<{descriptor.nativeType}, &{wrap}>"
        else:
            needReturnMethod = toStringBool(
                descriptor.interface.maplikeOrSetlikeOrIterable.getExtendedAttribute(
                    "GenerateReturnMethod"
                )
                is not None
            )
            wrap = f"{descriptor.interface.identifier.name}AsyncIterator_Binding::Wrap"
            iterClass = f"mozilla::dom::binding_detail::WrappableAsyncIterableIterator<{descriptor.nativeType}, {needReturnMethod}, &{wrap}>"

        createIterator = fill(
            """
            typedef ${iterClass} itrType;
            RefPtr<itrType> result(new itrType(self,
                                               itrType::IteratorType::${itrMethod}));
            """,
            iterClass=iterClass,
            itrMethod=methodName.title(),
        )

        if descriptor.interface.isAsyncIterable():
            args.append("initError")
            createIterator = fill(
                """
                $*{createIterator}
                {
                  ErrorResult initError;
                  self->InitAsyncIteratorData(result->Data(), itrType::IteratorType::${itrMethod}, ${args});
                  if (initError.MaybeSetPendingException(cx, "Asynchronous iterator initialization steps for ${ifaceName} failed")) {
                    return false;
                  }
                }
                """,
                createIterator=createIterator,
                itrMethod=methodName.title(),
                args=", ".join(args),
                ifaceName=descriptor.interface.identifier.name,
            )

        CGGeneric.__init__(self, createIterator)


def getObservableArrayBackingObject(descriptor, attr, errorReturn="return false;\n"):
    """
    Generate code to get/create a JS backing list for an observableArray attribute
    from the declaration slot.
    """
    assert attr.isAttr()
    assert attr.type.isObservableArray()

    # GetObservableArrayBackingObject may return a wrapped object for Xrays, so
    # when we create it we need to unwrap it to store the interface in the
    # reserved slot.
    return fill(
        """
        JS::Rooted<JSObject*> backingObj(cx);
        bool created = false;
        if (!GetObservableArrayBackingObject(cx, obj, ${slot},
                &backingObj, &created, ${namespace}::ObservableArrayProxyHandler::getInstance(),
                self)) {
          $*{errorReturn}
        }
        if (created) {
          PreserveWrapper(self);
        }
        """,
        namespace=toBindingNamespace(MakeNativeName(attr.identifier.name)),
        slot=memberReservedSlot(attr, descriptor),
        errorReturn=errorReturn,
        selfType=descriptor.nativeType,
    )


def getObservableArrayGetterBody(descriptor, attr):
    """
    Creates the body for the getter method of an observableArray attribute.
    """
    assert attr.type.isObservableArray()
    return fill(
        """
        $*{getBackingObj}
        MOZ_ASSERT(!JS_IsExceptionPending(cx));
        args.rval().setObject(*backingObj);
        return true;
        """,
        getBackingObj=getObservableArrayBackingObject(descriptor, attr),
    )


class CGObservableArrayProxyHandler_callback(ClassMethod):
    """
    Base class for declaring and defining the hook methods for ObservableArrayProxyHandler
    subclasses to get the interface native object from backing object and calls
    its On{Set|Delete}* callback.

     * 'callbackType': "Set" or "Delete".
     * 'invalidTypeFatal' (optional): If True, we don't expect the type
                                      conversion would fail, so generate the
                                      assertion code if type conversion fails.
    """

    def __init__(
        self, descriptor, attr, name, args, callbackType, invalidTypeFatal=False
    ):
        assert attr.isAttr()
        assert attr.type.isObservableArray()
        assert callbackType in ["Set", "Delete"]
        self.descriptor = descriptor
        self.attr = attr
        self.innertype = attr.type.inner
        self.callbackType = callbackType
        self.invalidTypeFatal = invalidTypeFatal
        ClassMethod.__init__(
            self,
            name,
            "bool",
            args,
            visibility="protected",
            virtual=True,
            override=True,
            const=True,
        )

    def preConversion(self):
        """
        The code to run before the conversion steps.
        """
        return ""

    def preCallback(self):
        """
        The code to run before calling the callback.
        """
        return ""

    def postCallback(self):
        """
        The code to run after calling the callback, all subclasses should override
        this to generate the return values.
        """
        assert False  # Override me!

    def getBody(self):
        exceptionCode = (
            fill(
                """
                MOZ_ASSERT_UNREACHABLE("The item in ObservableArray backing list is not ${innertype}?");
                return false;
                """,
                innertype=self.innertype,
            )
            if self.invalidTypeFatal
            else None
        )
        convertType = instantiateJSToNativeConversion(
            getJSToNativeConversionInfo(
                self.innertype,
                self.descriptor,
                sourceDescription="Element in ObservableArray backing list",
                exceptionCode=exceptionCode,
            ),
            {
                "declName": "decl",
                "holderName": "holder",
                "val": "aValue",
            },
        )
        callbackArgs = ["decl", "aIndex", "rv"]
        if typeNeedsCx(self.innertype):
            callbackArgs.insert(0, "cx")
        return fill(
            """
            MOZ_ASSERT(IsObservableArrayProxy(aProxy));
            $*{preConversion}

            BindingCallContext cx(aCx, "ObservableArray ${name}");
            $*{convertType}

            $*{preCallback}
            JS::Value val = js::GetProxyReservedSlot(aProxy, OBSERVABLE_ARRAY_DOM_INTERFACE_SLOT);
            auto* interface = static_cast<${ifaceType}*>(val.toPrivate());
            MOZ_ASSERT(interface);

            ErrorResult rv;
            MOZ_KnownLive(interface)->${methodName}(${callbackArgs});
            $*{postCallback}
            """,
            preConversion=self.preConversion(),
            name=self.name,
            convertType=convertType.define(),
            preCallback=self.preCallback(),
            ifaceType=self.descriptor.nativeType,
            methodName="On%s%s"
            % (self.callbackType, MakeNativeName(self.attr.identifier.name)),
            callbackArgs=", ".join(callbackArgs),
            postCallback=self.postCallback(),
        )


class CGObservableArrayProxyHandler_OnDeleteItem(
    CGObservableArrayProxyHandler_callback
):
    """
    Declares and defines the hook methods for ObservableArrayProxyHandler
    subclasses to get the interface native object from backing object and calls
    its OnDelete* callback.
    """

    def __init__(self, descriptor, attr):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("JS::Handle<JSObject*>", "aProxy"),
            Argument("JS::Handle<JS::Value>", "aValue"),
            Argument("uint32_t", "aIndex"),
        ]
        CGObservableArrayProxyHandler_callback.__init__(
            self,
            descriptor,
            attr,
            "OnDeleteItem",
            args,
            "Delete",
            True,
        )

    def postCallback(self):
        return dedent(
            """
            return !rv.MaybeSetPendingException(cx);
            """
        )


class CGObservableArrayProxyHandler_SetIndexedValue(
    CGObservableArrayProxyHandler_callback
):
    """
    Declares and defines the hook methods for ObservableArrayProxyHandler
    subclasses to run the setting the indexed value steps.
    """

    def __init__(self, descriptor, attr):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("JS::Handle<JSObject*>", "aProxy"),
            Argument("JS::Handle<JSObject*>", "aBackingList"),
            Argument("uint32_t", "aIndex"),
            Argument("JS::Handle<JS::Value>", "aValue"),
            Argument("JS::ObjectOpResult&", "aResult"),
        ]
        CGObservableArrayProxyHandler_callback.__init__(
            self,
            descriptor,
            attr,
            "SetIndexedValue",
            args,
            "Set",
        )

    def preConversion(self):
        return dedent(
            """
            uint32_t oldLen;
            if (!JS::GetArrayLength(aCx, aBackingList, &oldLen)) {
              return false;
            }

            if (aIndex > oldLen) {
              return aResult.failBadIndex();
            }
            """
        )

    def preCallback(self):
        return dedent(
            """
            if (aIndex < oldLen) {
              JS::Rooted<JS::Value> value(aCx);
              if (!JS_GetElement(aCx, aBackingList, aIndex, &value)) {
                return false;
              }

              if (!OnDeleteItem(aCx, aProxy, value, aIndex)) {
                return false;
              }
            }

            """
        )

    def postCallback(self):
        return dedent(
            """
            if (rv.MaybeSetPendingException(cx)) {
              return false;
            }

            if (!JS_SetElement(aCx, aBackingList, aIndex, aValue)) {
              return false;
            }

            return aResult.succeed();
            """
        )


class CGObservableArrayProxyHandler(CGThing):
    """
    A class for declaring a ObservableArrayProxyHandler.
    """

    def __init__(self, descriptor, attr):
        assert attr.isAttr()
        assert attr.type.isObservableArray()
        methods = [
            # The item stored in backing object should always be converted successfully.
            CGObservableArrayProxyHandler_OnDeleteItem(descriptor, attr),
            CGObservableArrayProxyHandler_SetIndexedValue(descriptor, attr),
            CGJSProxyHandler_getInstance("ObservableArrayProxyHandler"),
        ]
        parentClass = "mozilla::dom::ObservableArrayProxyHandler"
        self.proxyHandler = CGClass(
            "ObservableArrayProxyHandler",
            bases=[ClassBase(parentClass)],
            constructors=[],
            methods=methods,
        )

    def declare(self):
        # Our class declaration should happen when we're defining
        return ""

    def define(self):
        return self.proxyHandler.declare() + "\n" + self.proxyHandler.define()


class CGObservableArrayProxyHandlerGenerator(CGNamespace):
    """
    Declares and defines convenience methods for accessing backing list objects
    for observable array attribute. Generates function signatures, un/packs
    backing list objects from slot, etc.
    """

    def __init__(self, descriptor, attr):
        assert attr.isAttr()
        assert attr.type.isObservableArray()
        namespace = toBindingNamespace(MakeNativeName(attr.identifier.name))
        proxyHandler = CGObservableArrayProxyHandler(descriptor, attr)
        CGNamespace.__init__(self, namespace, proxyHandler)


class CGObservableArraySetterGenerator(CGGeneric):
    """
    Creates setter for an observableArray attributes.
    """

    def __init__(self, descriptor, attr):
        assert attr.isAttr()
        assert attr.type.isObservableArray()
        getBackingObject = getObservableArrayBackingObject(descriptor, attr)
        setElement = dedent(
            """
            if (!JS_SetElement(cx, backingObj, i, val)) {
              return false;
            }
            """
        )
        conversion = wrapForType(
            attr.type.inner,
            descriptor,
            {
                "result": "arg0.ElementAt(i)",
                "successCode": setElement,
                "jsvalRef": "val",
                "jsvalHandle": "&val",
            },
        )
        CGGeneric.__init__(
            self,
            fill(
                """
                if (xpc::WrapperFactory::IsXrayWrapper(obj)) {
                  JS_ReportErrorASCII(cx, "Accessing from Xray wrapper is not supported.");
                  return false;
                }

                ${getBackingObject}
                const ObservableArrayProxyHandler* handler = GetObservableArrayProxyHandler(backingObj);
                if (!handler->SetLength(cx, backingObj, 0)) {
                  return false;
                }

                JS::Rooted<JS::Value> val(cx);
                for (size_t i = 0; i < arg0.Length(); i++) {
                  $*{conversion}
                }
                """,
                conversion=conversion,
                getBackingObject=getBackingObject,
            ),
        )


class CGObservableArrayHelperFunctionGenerator(CGHelperFunctionGenerator):
    """
    Generates code to allow C++ to perform operations on backing objects. Gets
    a context from the binding wrapper, turns arguments into JS::Values (via
    CallbackMember/CGNativeMember argument conversion), then uses
    MethodBodyGenerator to generate the body.
    """

    class MethodBodyGenerator(CGThing):
        """
        Creates methods body for observable array attribute. It is expected that all
        methods will be have a maplike/setlike object attached. Unwrapping/wrapping
        will be taken care of by the usual method generation machinery in
        CGMethodCall/CGPerSignatureCall. Functionality is filled in here instead of
        using CGCallGenerator.
        """

        def __init__(
            self,
            descriptor,
            attr,
            methodName,
            helperGenerator,
            needsIndexArg,
        ):
            assert attr.isAttr()
            assert attr.type.isObservableArray()

            CGThing.__init__(self)
            self.helperGenerator = helperGenerator
            self.cgRoot = CGList([])

            self.cgRoot.append(
                CGGeneric(
                    getObservableArrayBackingObject(
                        descriptor,
                        attr,
                        dedent(
                            """
                            aRv.Throw(NS_ERROR_UNEXPECTED);
                            return%s;
                            """
                            % helperGenerator.getDefaultRetval()
                        ),
                    )
                )
            )

            # Generates required code for the method. Method descriptions included
            # in definitions below. Throw if we don't have a method to fill in what
            # we're looking for.
            try:
                methodGenerator = getattr(self, methodName)
            except AttributeError:
                raise TypeError(
                    "Missing observable array method definition '%s'" % methodName
                )
            # Method generator returns tuple, containing:
            #
            # - a list of CGThings representing setup code for preparing to call
            #   the JS API function
            # - JS API function name
            # - a list of arguments needed for the JS API function we're calling
            # - a list of CGThings representing code needed before return.
            (setupCode, funcName, arguments, returnCode) = methodGenerator()

            # Append the list of setup code CGThings
            self.cgRoot.append(CGList(setupCode))
            # Create the JS API call
            if needsIndexArg:
                arguments.insert(0, "aIndex")
            self.cgRoot.append(
                CGWrapper(
                    CGGeneric(
                        fill(
                            """
                            aRv.MightThrowJSException();
                            if (!${funcName}(${args})) {
                              aRv.StealExceptionFromJSContext(cx);
                              return${retval};
                            }
                            """,
                            funcName=funcName,
                            args=", ".join(["cx", "backingObj"] + arguments),
                            retval=helperGenerator.getDefaultRetval(),
                        )
                    )
                )
            )
            # Append code before return
            self.cgRoot.append(CGList(returnCode))

        def elementat(self):
            setupCode = []
            if not self.helperGenerator.needsScopeBody():
                setupCode.append(CGGeneric("JS::Rooted<JS::Value> result(cx);\n"))
            returnCode = [
                CGGeneric(
                    fill(
                        """
                        if (result.isUndefined()) {
                          aRv.Throw(NS_ERROR_NOT_AVAILABLE);
                          return${retval};
                        }
                        """,
                        retval=self.helperGenerator.getDefaultRetval(),
                    )
                )
            ]
            return (setupCode, "JS_GetElement", ["&result"], returnCode)

        def replaceelementat(self):
            setupCode = [
                CGGeneric(
                    fill(
                        """
                        uint32_t length;
                        aRv.MightThrowJSException();
                        if (!JS::GetArrayLength(cx, backingObj, &length)) {
                          aRv.StealExceptionFromJSContext(cx);
                          return${retval};
                        }
                        if (aIndex > length) {
                          aRv.ThrowRangeError("Invalid index");
                          return${retval};
                        }
                        """,
                        retval=self.helperGenerator.getDefaultRetval(),
                    )
                )
            ]
            return (setupCode, "JS_SetElement", ["argv[0]"], [])

        def appendelement(self):
            setupCode = [
                CGGeneric(
                    fill(
                        """
                        uint32_t length;
                        aRv.MightThrowJSException();
                        if (!JS::GetArrayLength(cx, backingObj, &length)) {
                          aRv.StealExceptionFromJSContext(cx);
                          return${retval};
                        }
                        """,
                        retval=self.helperGenerator.getDefaultRetval(),
                    )
                )
            ]
            return (setupCode, "JS_SetElement", ["length", "argv[0]"], [])

        def removelastelement(self):
            setupCode = [
                CGGeneric(
                    fill(
                        """
                        uint32_t length;
                        aRv.MightThrowJSException();
                        if (!JS::GetArrayLength(cx, backingObj, &length)) {
                          aRv.StealExceptionFromJSContext(cx);
                          return${retval};
                        }
                        if (length == 0) {
                          aRv.Throw(NS_ERROR_NOT_AVAILABLE);
                          return${retval};
                        }
                        """,
                        retval=self.helperGenerator.getDefaultRetval(),
                    )
                )
            ]
            return (setupCode, "JS::SetArrayLength", ["length - 1"], [])

        def length(self):
            return (
                [CGGeneric("uint32_t retVal;\n")],
                "JS::GetArrayLength",
                ["&retVal"],
                [],
            )

        def define(self):
            return self.cgRoot.define()

    def __init__(
        self,
        descriptor,
        attr,
        name,
        returnType=BuiltinTypes[IDLBuiltinType.Types.undefined],
        needsResultConversion=True,
        needsIndexArg=False,
        needsValueArg=False,
    ):
        assert attr.isAttr()
        assert attr.type.isObservableArray()
        self.attr = attr
        self.needsIndexArg = needsIndexArg

        args = []
        if needsValueArg:
            args.append(FakeArgument(attr.type.inner, "aValue"))

        CGHelperFunctionGenerator.__init__(
            self,
            descriptor,
            name,
            args,
            returnType,
            needsResultConversion,
        )

    def getArgs(self, returnType, argList):
        if self.needsIndexArg:
            argList = [
                FakeArgument(BuiltinTypes[IDLBuiltinType.Types.unsigned_long], "aIndex")
            ] + argList
        return CGHelperFunctionGenerator.getArgs(self, returnType, argList)

    def getCall(self):
        return CGObservableArrayHelperFunctionGenerator.MethodBodyGenerator(
            self.descriptorProvider,
            self.attr,
            self.name.lower(),
            self,
            self.needsIndexArg,
        ).define()


class CGObservableArrayHelperGenerator(CGNamespace):
    """
    Declares and defines convenience methods for accessing backing object for
    observable array type. Generates function signatures, un/packs
    backing objects from slot, etc.
    """

    def __init__(self, descriptor, attr):
        assert attr.isAttr()
        assert attr.type.isObservableArray()

        namespace = "%sHelpers" % MakeNativeName(attr.identifier.name)
        helpers = [
            CGObservableArrayHelperFunctionGenerator(
                descriptor,
                attr,
                "ElementAt",
                returnType=attr.type.inner,
                needsIndexArg=True,
            ),
            CGObservableArrayHelperFunctionGenerator(
                descriptor,
                attr,
                "ReplaceElementAt",
                needsIndexArg=True,
                needsValueArg=True,
            ),
            CGObservableArrayHelperFunctionGenerator(
                descriptor,
                attr,
                "AppendElement",
                needsValueArg=True,
            ),
            CGObservableArrayHelperFunctionGenerator(
                descriptor,
                attr,
                "RemoveLastElement",
            ),
            CGObservableArrayHelperFunctionGenerator(
                descriptor,
                attr,
                "Length",
                returnType=BuiltinTypes[IDLBuiltinType.Types.unsigned_long],
                needsResultConversion=False,
            ),
        ]
        CGNamespace.__init__(self, namespace, CGList(helpers, "\n"))


class GlobalGenRoots:
    """
    Roots for global codegen.

    To generate code, call the method associated with the target, and then
    call the appropriate define/declare method.
    """

    @staticmethod
    def GeneratedAtomList(config):
        # Atom enum
        dictionaries = config.dictionaries

        structs = []

        def memberToAtomCacheMember(binaryNameFor, m):
            binaryMemberName = binaryNameFor(m)
            return ClassMember(
                CGDictionary.makeIdName(binaryMemberName),
                "PinnedStringId",
                visibility="public",
            )

        def buildAtomCacheStructure(idlobj, binaryNameFor, members):
            classMembers = [memberToAtomCacheMember(binaryNameFor, m) for m in members]
            structName = idlobj.identifier.name + "Atoms"
            return (
                structName,
                CGWrapper(
                    CGClass(
                        structName, bases=None, isStruct=True, members=classMembers
                    ),
                    post="\n",
                ),
            )

        for dict in dictionaries:
            if len(dict.members) == 0:
                continue

            structs.append(
                buildAtomCacheStructure(dict, lambda m: m.identifier.name, dict.members)
            )

        for d in config.getDescriptors(isJSImplemented=True) + config.getDescriptors(
            isCallback=True
        ):
            members = [m for m in d.interface.members if m.isAttr() or m.isMethod()]
            if d.interface.isJSImplemented() and d.interface.ctor():
                # We'll have an __init() method.
                members.append(FakeMember("__init"))
            if d.interface.isJSImplemented() and d.interface.getExtendedAttribute(
                "WantsEventListenerHooks"
            ):
                members.append(FakeMember("eventListenerAdded"))
                members.append(FakeMember("eventListenerRemoved"))
            if len(members) == 0:
                continue

            structs.append(
                buildAtomCacheStructure(
                    d.interface,
                    lambda m: d.binaryNameFor(m.identifier.name, m.isStatic()),
                    members,
                )
            )

        structs.sort()
        generatedStructs = [struct for structName, struct in structs]
        structNames = [structName for structName, struct in structs]

        mainStruct = CGWrapper(
            CGClass(
                "PerThreadAtomCache",
                bases=[ClassBase(structName) for structName in structNames],
                isStruct=True,
            ),
            post="\n",
        )

        structs = CGList(generatedStructs + [mainStruct])

        # Wrap all of that in our namespaces.
        curr = CGNamespace.build(["mozilla", "dom"], CGWrapper(structs, pre="\n"))
        curr = CGWrapper(curr, post="\n")

        # Add include statement for PinnedStringId.
        declareIncludes = ["mozilla/dom/PinnedStringId.h"]
        curr = CGHeaders([], [], [], [], declareIncludes, [], "GeneratedAtomList", curr)

        # Add include guards.
        curr = CGIncludeGuard("GeneratedAtomList", curr)

        # Add the auto-generated comment.
        curr = CGWrapper(curr, pre=AUTOGENERATED_WARNING_COMMENT)

        # Done.
        return curr

    @staticmethod
    def GeneratedEventList(config):
        eventList = CGList([])
        for generatedEvent in config.generatedEvents:
            eventList.append(
                CGGeneric(declare=("GENERATED_EVENT(%s)\n" % generatedEvent))
            )
        return eventList

    @staticmethod
    def PrototypeList(config):
        # Prototype ID enum.
        descriptorsWithPrototype = config.getDescriptors(
            hasInterfacePrototypeObject=True
        )
        descriptorsWithPrototype.extend(
            config.getDescriptors(hasOrdinaryObjectPrototype=True)
        )
        descriptorsWithPrototype.sort(key=attrgetter("name"))
        protos = [d.name for d in descriptorsWithPrototype]
        idEnum = CGNamespacedEnum("id", "ID", ["_ID_Start"] + protos, [0, "_ID_Start"])
        idEnum = CGList([idEnum])

        def fieldSizeAssert(amount, jitInfoField, message):
            maxFieldValue = (
                "(uint64_t(1) << (sizeof(std::declval<JSJitInfo>().%s) * 8))"
                % jitInfoField
            )
            return CGGeneric(
                define='static_assert(%s < %s, "%s");\n\n'
                % (amount, maxFieldValue, message)
            )

        idEnum.append(
            fieldSizeAssert("id::_ID_Count", "protoID", "Too many prototypes!")
        )

        # Wrap all of that in our namespaces.
        idEnum = CGNamespace.build(
            ["mozilla", "dom", "prototypes"], CGWrapper(idEnum, pre="\n")
        )
        idEnum = CGWrapper(idEnum, post="\n")

        curr = CGList(
            [
                CGGeneric(define="#include <stdint.h>\n"),
                CGGeneric(define="#include <type_traits>\n\n"),
                CGGeneric(define='#include "js/experimental/JitInfo.h"\n\n'),
                CGGeneric(define='#include "mozilla/dom/BindingNames.h"\n\n'),
                CGGeneric(define='#include "mozilla/dom/PrototypeList.h"\n\n'),
                idEnum,
            ]
        )

        # Let things know the maximum length of the prototype chain.
        maxMacroName = "MAX_PROTOTYPE_CHAIN_LENGTH"
        maxMacro = CGGeneric(
            declare="#define " + maxMacroName + " " + str(config.maxProtoChainLength)
        )
        curr.append(CGWrapper(maxMacro, post="\n\n"))
        curr.append(
            fieldSizeAssert(
                maxMacroName, "depth", "Some inheritance chain is too long!"
            )
        )

        # Constructor ID enum.
        constructors = [d.name for d in config.getDescriptors(hasInterfaceObject=True)]
        idEnum = CGNamespacedEnum(
            "id",
            "ID",
            ["_ID_Start"] + constructors,
            ["prototypes::id::_ID_Count", "_ID_Start"],
        )

        # Wrap all of that in our namespaces.
        idEnum = CGNamespace.build(
            ["mozilla", "dom", "constructors"], CGWrapper(idEnum, pre="\n")
        )
        idEnum = CGWrapper(idEnum, post="\n")

        curr.append(idEnum)

        # Named properties object enum.
        namedPropertiesObjects = [
            d.name for d in config.getDescriptors(hasNamedPropertiesObject=True)
        ]
        idEnum = CGNamespacedEnum(
            "id",
            "ID",
            ["_ID_Start"] + namedPropertiesObjects,
            ["constructors::id::_ID_Count", "_ID_Start"],
        )

        # Wrap all of that in our namespaces.
        idEnum = CGNamespace.build(
            ["mozilla", "dom", "namedpropertiesobjects"], CGWrapper(idEnum, pre="\n")
        )
        idEnum = CGWrapper(idEnum, post="\n")

        curr.append(idEnum)

        traitsDecls = [
            CGGeneric(
                declare=dedent(
                    """
            template <prototypes::ID PrototypeID>
            struct PrototypeTraits;
            """
                )
            )
        ]
        traitsDecls.extend(CGPrototypeTraitsClass(d) for d in descriptorsWithPrototype)

        ifaceNamesWithProto = [
            d.interface.getClassName() for d in descriptorsWithPrototype
        ]
        traitsDecls.append(
            CGStringTable("NamesOfInterfacesWithProtos", ifaceNamesWithProto)
        )

        traitsDecl = CGNamespace.build(["mozilla", "dom"], CGList(traitsDecls))

        curr.append(traitsDecl)

        # Add include guards.
        curr = CGIncludeGuard("PrototypeList", curr)

        # Add the auto-generated comment.
        curr = CGWrapper(curr, pre=AUTOGENERATED_WARNING_COMMENT)

        # Done.
        return curr

    @staticmethod
    def BindingNames(config):
        declare = fill(
            """
            enum class BindingNamesOffset : uint16_t {
              $*{enumValues}
            };

            namespace binding_detail {
            extern const char sBindingNames[];
            }  // namespace binding_detail

            MOZ_ALWAYS_INLINE const char* BindingName(BindingNamesOffset aOffset) {
              return binding_detail::sBindingNames + static_cast<size_t>(aOffset);
            }
            """,
            enumValues="".join(
                "%s = %i,\n" % (BindingNamesOffsetEnum(n), o)
                for (n, o) in config.namesStringOffsets
            ),
        )
        define = fill(
            """
            namespace binding_detail {

            const char sBindingNames[] = {
              $*{namesString}
            };

            }  // namespace binding_detail

            // Making this enum bigger than a uint16_t has consequences on the size
            // of some structs (eg. WebIDLNameTableEntry) and tables. We should try
            // to avoid that.
            static_assert(EnumTypeFitsWithin<BindingNamesOffset, uint16_t>::value,
                          "Size increase");
            """,
            namesString=' "\\0"\n'.join(
                '/* %5i */ "%s"' % (o, n) for (n, o) in config.namesStringOffsets
            )
            + "\n",
        )

        curr = CGGeneric(declare=declare, define=define)
        curr = CGWrapper(curr, pre="\n", post="\n")

        curr = CGNamespace.build(["mozilla", "dom"], curr)
        curr = CGWrapper(curr, post="\n")

        curr = CGHeaders(
            [],
            [],
            [],
            [],
            ["<stddef.h>", "<stdint.h>", "mozilla/Attributes.h"],
            ["mozilla/dom/BindingNames.h", "mozilla/EnumTypeTraits.h"],
            "BindingNames",
            curr,
        )

        # Add include guards.
        curr = CGIncludeGuard("BindingNames", curr)

        # Done.
        return curr

    @staticmethod
    def RegisterBindings(config):
        curr = CGNamespace.build(
            ["mozilla", "dom"], CGGlobalNames(config.windowGlobalNames)
        )
        curr = CGWrapper(curr, post="\n")

        # Add the includes
        defineIncludes = [
            CGHeaders.getDeclarationFilename(desc.interface)
            for desc in config.getDescriptors(
                hasInterfaceObject=True, isExposedInWindow=True, register=True
            )
        ]
        defineIncludes.append("mozilla/dom/BindingNames.h")
        defineIncludes.append("mozilla/dom/WebIDLGlobalNameHash.h")
        defineIncludes.append("mozilla/dom/PrototypeList.h")
        defineIncludes.append("mozilla/PerfectHash.h")
        defineIncludes.append("js/String.h")
        curr = CGHeaders([], [], [], [], [], defineIncludes, "RegisterBindings", curr)

        # Add include guards.
        curr = CGIncludeGuard("RegisterBindings", curr)

        # Done.
        return curr

    @staticmethod
    def RegisterWorkerBindings(config):
        curr = CGRegisterWorkerBindings(config)

        # Wrap all of that in our namespaces.
        curr = CGNamespace.build(["mozilla", "dom"], CGWrapper(curr, post="\n"))
        curr = CGWrapper(curr, post="\n")

        # Add the includes
        defineIncludes = [
            CGHeaders.getDeclarationFilename(desc.interface)
            for desc in config.getDescriptors(
                hasInterfaceObject=True, register=True, isExposedInAnyWorker=True
            )
        ]

        curr = CGHeaders(
            [], [], [], [], [], defineIncludes, "RegisterWorkerBindings", curr
        )

        # Add include guards.
        curr = CGIncludeGuard("RegisterWorkerBindings", curr)

        # Done.
        return curr

    @staticmethod
    def RegisterWorkerDebuggerBindings(config):
        curr = CGRegisterWorkerDebuggerBindings(config)

        # Wrap all of that in our namespaces.
        curr = CGNamespace.build(["mozilla", "dom"], CGWrapper(curr, post="\n"))
        curr = CGWrapper(curr, post="\n")

        # Add the includes
        defineIncludes = [
            CGHeaders.getDeclarationFilename(desc.interface)
            for desc in config.getDescriptors(
                hasInterfaceObject=True, register=True, isExposedInWorkerDebugger=True
            )
        ]

        curr = CGHeaders(
            [], [], [], [], [], defineIncludes, "RegisterWorkerDebuggerBindings", curr
        )

        # Add include guards.
        curr = CGIncludeGuard("RegisterWorkerDebuggerBindings", curr)

        # Done.
        return curr

    @staticmethod
    def RegisterWorkletBindings(config):
        curr = CGRegisterWorkletBindings(config)

        # Wrap all of that in our namespaces.
        curr = CGNamespace.build(["mozilla", "dom"], CGWrapper(curr, post="\n"))
        curr = CGWrapper(curr, post="\n")

        # Add the includes
        defineIncludes = [
            CGHeaders.getDeclarationFilename(desc.interface)
            for desc in config.getDescriptors(
                hasInterfaceObject=True, register=True, isExposedInAnyWorklet=True
            )
        ]

        curr = CGHeaders(
            [], [], [], [], [], defineIncludes, "RegisterWorkletBindings", curr
        )

        # Add include guards.
        curr = CGIncludeGuard("RegisterWorkletBindings", curr)

        # Done.
        return curr

    @staticmethod
    def RegisterShadowRealmBindings(config):
        curr = CGRegisterShadowRealmBindings(config)

        # Wrap all of that in our namespaces.
        curr = CGNamespace.build(["mozilla", "dom"], CGWrapper(curr, post="\n"))
        curr = CGWrapper(curr, post="\n")

        # Add the includes
        defineIncludes = [
            CGHeaders.getDeclarationFilename(desc.interface)
            for desc in config.getDescriptors(
                hasInterfaceObject=True, register=True, isExposedInShadowRealms=True
            )
        ]

        curr = CGHeaders(
            [], [], [], [], [], defineIncludes, "RegisterShadowRealmBindings", curr
        )

        # Add include guards.
        curr = CGIncludeGuard("RegisterShadowRealmBindings", curr)

        # Done.
        return curr

    @staticmethod
    def UnionTypes(config):
        unionTypes = UnionsForFile(config, None)
        (
            includes,
            implincludes,
            declarations,
            traverseMethods,
            unlinkMethods,
            unionStructs,
        ) = UnionTypes(unionTypes, config)

        unionStructs = dependencySortDictionariesAndUnionsAndCallbacks(unionStructs)

        unions = CGList(
            traverseMethods
            + unlinkMethods
            + [CGUnionStruct(t, config) for t in unionStructs]
            + [CGUnionStruct(t, config, True) for t in unionStructs],
            "\n",
        )

        includes.add("mozilla/OwningNonNull.h")
        includes.add("mozilla/dom/UnionMember.h")
        includes.add("mozilla/dom/BindingDeclarations.h")
        # BindingUtils.h is only needed for SetToObject.
        # If it stops being inlined or stops calling CallerSubsumes
        # both this bit and the bit in CGBindingRoot can be removed.
        includes.add("mozilla/dom/BindingUtils.h")

        # Wrap all of that in our namespaces.
        curr = CGNamespace.build(["mozilla", "dom"], unions)

        curr = CGWrapper(curr, post="\n")

        builder = ForwardDeclarationBuilder()
        for className, isStruct in declarations:
            builder.add(className, isStruct=isStruct)

        curr = CGList([builder.build(), curr], "\n")

        curr = CGHeaders([], [], [], [], includes, implincludes, "UnionTypes", curr)

        # Add include guards.
        curr = CGIncludeGuard("UnionTypes", curr)

        # Done.
        return curr

    @staticmethod
    def WebIDLPrefs(config):
        prefs = set()
        headers = set(["mozilla/dom/WebIDLPrefs.h"])
        for d in config.getDescriptors(hasInterfaceOrInterfacePrototypeObject=True):
            for m in d.interface.members:
                pref = PropertyDefiner.getStringAttr(m, "Pref")
                if pref:
                    headers.add(prefHeader(pref))
                    prefs.add((pref, prefIdentifier(pref)))
        prefs = sorted(prefs)
        declare = fill(
            """
            enum class WebIDLPrefIndex : uint8_t {
              NoPref,
              $*{prefs}
            };
            typedef bool (*WebIDLPrefFunc)();
            extern const WebIDLPrefFunc sWebIDLPrefs[${len}];
            """,
            prefs=",\n".join(map(lambda p: "// " + p[0] + "\n" + p[1], prefs)) + "\n",
            len=len(prefs) + 1,
        )
        define = fill(
            """
            const WebIDLPrefFunc sWebIDLPrefs[] = {
              nullptr,
              $*{prefs}
            };
            """,
            prefs=",\n".join(
                map(lambda p: "// " + p[0] + "\nStaticPrefs::" + p[1], prefs)
            )
            + "\n",
        )
        prefFunctions = CGGeneric(declare=declare, define=define)

        # Wrap all of that in our namespaces.
        curr = CGNamespace.build(["mozilla", "dom"], prefFunctions)

        curr = CGWrapper(curr, post="\n")

        curr = CGHeaders([], [], [], [], [], headers, "WebIDLPrefs", curr)

        # Add include guards.
        curr = CGIncludeGuard("WebIDLPrefs", curr)

        # Done.
        return curr

    @staticmethod
    def WebIDLSerializable(config):
        # We need a declaration of StructuredCloneTags in the header.
        declareIncludes = set(
            [
                "mozilla/dom/DOMJSClass.h",
                "mozilla/dom/StructuredCloneTags.h",
                "js/TypeDecls.h",
            ]
        )
        defineIncludes = set(
            ["mozilla/dom/WebIDLSerializable.h", "mozilla/PerfectHash.h"]
        )
        names = list()
        for d in config.getDescriptors(isSerializable=True):
            names.append(d.name)
            defineIncludes.add(CGHeaders.getDeclarationFilename(d.interface))

        if len(names) == 0:
            # We can't really create a PerfectHash out of this, but also there's
            # not much point to this file if we have no [Serializable] objects.
            # Just spit out an empty file.
            return CGIncludeGuard("WebIDLSerializable", CGGeneric(""))

        # If we had a lot of serializable things, it might be worth it to use a
        # PerfectHash here, or an array ordered by sctag value and binary
        # search.  But setting those up would require knowing in this python
        # code the values of the various SCTAG_DOM_*.  We could hardcode them
        # here and add static asserts that the values are right, or switch to
        # code-generating StructuredCloneTags.h or something.  But in practice,
        # there's a pretty small number of serializable interfaces, and just
        # doing a linear walk is fine.  It's not obviously worse than the
        # if-cascade we used to have.  Let's just make sure we notice if we do
        # end up with a lot of serializable things here.
        #
        # Also, in practice it looks like compilers compile this linear walk to
        # an out-of-bounds check followed by a direct index into an array, by
        # basically making a second copy of this array ordered by tag, with the
        # holes filled in.  Again, worth checking whether this still happens if
        # we have too many serializable things.
        if len(names) > 20:
            raise TypeError(
                "We now have %s serializable interfaces.  "
                "Double-check that the compiler is still "
                "generating a jump table." % len(names)
            )

        entries = list()
        # Make sure we have stable ordering.
        for name in sorted(names):
            exposedGlobals = computeGlobalNamesFromExposureSet(d.interface.exposureSet)
            # Strip off trailing newline to make our formatting look right.
            entries.append(
                fill(
                    """
                {
                  /* mTag */ ${tag},
                  /* mDeserialize */ ${name}_Binding::Deserialize,
                  /* mExposedGlobals */ ${exposedGlobals},
                }
                """,
                    tag=StructuredCloneTag(name),
                    name=name,
                    exposedGlobals=exposedGlobals,
                )[:-1]
            )

        declare = dedent(
            """
            Maybe<std::pair<uint16_t, WebIDLDeserializer>> LookupDeserializer(StructuredCloneTags aTag);
            """
        )
        define = fill(
            """
            struct WebIDLSerializableEntry {
              StructuredCloneTags mTag;
              WebIDLDeserializer mDeserialize;
              uint16_t mExposedGlobals;
            };

            static const WebIDLSerializableEntry sEntries[] = {
              $*{entries}
            };

            Maybe<std::pair<uint16_t, WebIDLDeserializer>> LookupDeserializer(StructuredCloneTags aTag) {
              for (auto& entry : sEntries) {
                if (entry.mTag == aTag) {
                  return Some(std::pair(entry.mExposedGlobals, entry.mDeserialize));
                }
              }
              return Nothing();
            }
            """,
            entries=",\n".join(entries) + "\n",
        )

        code = CGGeneric(declare=declare, define=define)

        # Wrap all of that in our namespaces.
        curr = CGNamespace.build(["mozilla", "dom"], code)

        curr = CGWrapper(curr, post="\n")

        curr = CGHeaders(
            [], [], [], [], declareIncludes, defineIncludes, "WebIDLSerializable", curr
        )

        # Add include guards.
        curr = CGIncludeGuard("WebIDLSerializable", curr)

        # Done.
        return curr


# Code generator for simple events
class CGEventGetter(CGNativeMember):
    def __init__(self, descriptor, attr):
        ea = descriptor.getExtendedAttributes(attr, getter=True)
        CGNativeMember.__init__(
            self,
            descriptor,
            attr,
            CGSpecializedGetterCommon.makeNativeName(descriptor, attr),
            (attr.type, []),
            ea,
            resultNotAddRefed=not attr.type.isSequence(),
        )
        self.body = self.getMethodBody()

    def getArgs(self, returnType, argList):
        if "needsErrorResult" in self.extendedAttrs:
            raise TypeError("Event code generator does not support [Throws]!")
        if "canOOM" in self.extendedAttrs:
            raise TypeError("Event code generator does not support [CanOOM]!")
        if not self.member.isAttr():
            raise TypeError("Event code generator does not support methods")
        if self.member.isStatic():
            raise TypeError("Event code generators does not support static attributes")
        return CGNativeMember.getArgs(self, returnType, argList)

    def getMethodBody(self):
        type = self.member.type
        memberName = CGDictionary.makeMemberName(self.member.identifier.name)
        if (
            (type.isPrimitive() and type.tag() in builtinNames)
            or type.isEnum()
            or type.isPromise()
            or type.isGeckoInterface()
        ):
            return "return " + memberName + ";\n"
        if type.isJSString():
            # https://bugzilla.mozilla.org/show_bug.cgi?id=1580167
            raise TypeError("JSString not supported as member of a generated event")
        if (
            type.isDOMString()
            or type.isByteString()
            or type.isUSVString()
            or type.isUTF8String()
        ):
            return "aRetVal = " + memberName + ";\n"
        if type.isSpiderMonkeyInterface() or type.isObject():
            return fill(
                """
                if (${memberName}) {
                  JS::ExposeObjectToActiveJS(${memberName});
                }
                aRetVal.set(${memberName});
                return;
                """,
                memberName=memberName,
            )
        if type.isAny():
            return fill(
                """
                ${selfName}(aRetVal);
                """,
                selfName=self.name,
            )
        if type.isUnion():
            return "aRetVal = " + memberName + ";\n"
        if type.isSequence():
            if type.nullable():
                return (
                    "if ("
                    + memberName
                    + ".IsNull()) { aRetVal.SetNull(); } else { aRetVal.SetValue("
                    + memberName
                    + ".Value().Clone()); }\n"
                )
            else:
                return "aRetVal = " + memberName + ".Clone();\n"
        if type.isDictionary():
            return "aRetVal = " + memberName + ";\n"
        raise TypeError("Event code generator does not support this type!")

    def declare(self, cgClass):
        if (
            getattr(self.member, "originatingInterface", cgClass.descriptor.interface)
            != cgClass.descriptor.interface
        ):
            return ""
        return CGNativeMember.declare(self, cgClass)

    def define(self, cgClass):
        if (
            getattr(self.member, "originatingInterface", cgClass.descriptor.interface)
            != cgClass.descriptor.interface
        ):
            return ""
        return CGNativeMember.define(self, cgClass)


class CGEventSetter(CGNativeMember):
    def __init__(self):
        raise TypeError("Event code generator does not support setters!")


class CGEventMethod(CGNativeMember):
    def __init__(self, descriptor, method, signature, isConstructor, breakAfter=True):
        self.isInit = False

        CGNativeMember.__init__(
            self,
            descriptor,
            method,
            CGSpecializedMethod.makeNativeName(descriptor, method),
            signature,
            descriptor.getExtendedAttributes(method),
            breakAfter=breakAfter,
            variadicIsSequence=True,
        )
        self.originalArgs = list(self.args)

        iface = descriptor.interface
        allowed = isConstructor
        if not allowed and iface.getExtendedAttribute("LegacyEventInit"):
            # Allow it, only if it fits the initFooEvent profile exactly
            # We could check the arg types but it's not worth the effort.
            if (
                method.identifier.name == "init" + iface.identifier.name
                and signature[1][0].type.isDOMString()
                and signature[1][1].type.isBoolean()
                and signature[1][2].type.isBoolean()
                and
                # -3 on the left to ignore the type, bubbles, and cancelable parameters
                # -1 on the right to ignore the .trusted property which bleeds through
                # here because it is [Unforgeable].
                len(signature[1]) - 3
                == len([x for x in iface.members if x.isAttr()]) - 1
            ):
                allowed = True
                self.isInit = True

        if not allowed:
            raise TypeError("Event code generator does not support methods!")

    def getArgs(self, returnType, argList):
        args = [self.getArg(arg) for arg in argList]
        return args

    def getArg(self, arg):
        decl, ref = self.getArgType(
            arg.type, arg.canHaveMissingValue(), "Variadic" if arg.variadic else False
        )
        if ref:
            decl = CGWrapper(decl, pre="const ", post="&")

        name = arg.identifier.name
        name = "a" + name[0].upper() + name[1:]
        return Argument(decl.define(), name)

    def declare(self, cgClass):
        if self.isInit:
            constructorForNativeCaller = ""
        else:
            self.args = list(self.originalArgs)
            self.args.insert(0, Argument("mozilla::dom::EventTarget*", "aOwner"))
            constructorForNativeCaller = CGNativeMember.declare(self, cgClass)

        self.args = list(self.originalArgs)
        if needCx(None, self.arguments(), [], considerTypes=True, static=True):
            self.args.insert(0, Argument("JSContext*", "aCx"))
        if not self.isInit:
            self.args.insert(0, Argument("const GlobalObject&", "aGlobal"))

        return constructorForNativeCaller + CGNativeMember.declare(self, cgClass)

    def defineInit(self, cgClass):
        iface = self.descriptorProvider.interface
        members = ""
        while iface.identifier.name != "Event":
            i = 3  # Skip the boilerplate args: type, bubble,s cancelable.
            for m in iface.members:
                if m.isAttr():
                    # We need to initialize all the member variables that do
                    # not come from Event.
                    if (
                        getattr(m, "originatingInterface", iface).identifier.name
                        == "Event"
                    ):
                        continue
                    name = CGDictionary.makeMemberName(m.identifier.name)
                    members += "%s = %s;\n" % (name, self.args[i].name)
                    i += 1
            iface = iface.parent

        self.body = fill(
            """
            InitEvent(${typeArg}, ${bubblesArg}, ${cancelableArg});
            ${members}
            """,
            typeArg=self.args[0].name,
            bubblesArg=self.args[1].name,
            cancelableArg=self.args[2].name,
            members=members,
        )

        return CGNativeMember.define(self, cgClass)

    def define(self, cgClass):
        self.args = list(self.originalArgs)
        if self.isInit:
            return self.defineInit(cgClass)
        members = ""
        holdJS = ""
        iface = self.descriptorProvider.interface
        while iface.identifier.name != "Event":
            for m in self.descriptorProvider.getDescriptor(
                iface.identifier.name
            ).interface.members:
                if m.isAttr():
                    # We initialize all the other member variables in the
                    # Constructor except those ones coming from the Event.
                    if (
                        getattr(
                            m, "originatingInterface", cgClass.descriptor.interface
                        ).identifier.name
                        == "Event"
                    ):
                        continue
                    name = CGDictionary.makeMemberName(m.identifier.name)
                    if m.type.isSequence():
                        # For sequences we may not be able to do a simple
                        # assignment because the underlying types may not match.
                        # For example, the argument can be a
                        # Sequence<OwningNonNull<SomeInterface>> while our
                        # member is an nsTArray<RefPtr<SomeInterface>>.  So
                        # use AppendElements, which is actually a template on
                        # the incoming type on nsTArray and does the right thing
                        # for this case.
                        target = name
                        source = "%s.%s" % (self.args[1].name, name)
                        sequenceCopy = "e->%s.AppendElements(%s);\n"
                        if m.type.nullable():
                            sequenceCopy = CGIfWrapper(
                                CGGeneric(sequenceCopy), "!%s.IsNull()" % source
                            ).define()
                            target += ".SetValue()"
                            source += ".Value()"
                        members += sequenceCopy % (target, source)
                    elif m.type.isSpiderMonkeyInterface():
                        srcname = "%s.%s" % (self.args[1].name, name)
                        if m.type.nullable():
                            members += fill(
                                """
                                if (${srcname}.IsNull()) {
                                  e->${varname} = nullptr;
                                } else {
                                  e->${varname} = ${srcname}.Value().Obj();
                                }
                                """,
                                varname=name,
                                srcname=srcname,
                            )
                        else:
                            members += fill(
                                """
                                e->${varname}.set(${srcname}.Obj());
                                """,
                                varname=name,
                                srcname=srcname,
                            )
                    else:
                        members += "e->%s = %s.%s;\n" % (name, self.args[1].name, name)
                    if (
                        m.type.isAny()
                        or m.type.isObject()
                        or m.type.isSpiderMonkeyInterface()
                    ):
                        holdJS = "mozilla::HoldJSObjects(e.get());\n"
            iface = iface.parent

        self.body = fill(
            """
            RefPtr<${nativeType}> e = new ${nativeType}(aOwner);
            bool trusted = e->Init(aOwner);
            e->InitEvent(${eventType}, ${eventInit}.mBubbles, ${eventInit}.mCancelable);
            $*{members}
            e->SetTrusted(trusted);
            e->SetComposed(${eventInit}.mComposed);
            $*{holdJS}
            return e.forget();
            """,
            nativeType=self.descriptorProvider.nativeType.split("::")[-1],
            eventType=self.args[0].name,
            eventInit=self.args[1].name,
            members=members,
            holdJS=holdJS,
        )

        self.args.insert(0, Argument("mozilla::dom::EventTarget*", "aOwner"))
        constructorForNativeCaller = CGNativeMember.define(self, cgClass) + "\n"
        self.args = list(self.originalArgs)
        self.body = fill(
            """
            nsCOMPtr<mozilla::dom::EventTarget> owner = do_QueryInterface(aGlobal.GetAsSupports());
            return Constructor(owner, ${arg0}, ${arg1});
            """,
            arg0=self.args[0].name,
            arg1=self.args[1].name,
        )
        if needCx(None, self.arguments(), [], considerTypes=True, static=True):
            self.args.insert(0, Argument("JSContext*", "aCx"))
        self.args.insert(0, Argument("const GlobalObject&", "aGlobal"))
        return constructorForNativeCaller + CGNativeMember.define(self, cgClass)


class CGEventClass(CGBindingImplClass):
    """
    Codegen for the actual Event class implementation for this descriptor
    """

    def __init__(self, descriptor):
        CGBindingImplClass.__init__(
            self,
            descriptor,
            CGEventMethod,
            CGEventGetter,
            CGEventSetter,
            False,
            "WrapObjectInternal",
        )
        members = []
        extraMethods = []
        self.membersNeedingCC = []
        self.membersNeedingTrace = []

        for m in descriptor.interface.members:
            if (
                getattr(m, "originatingInterface", descriptor.interface)
                != descriptor.interface
            ):
                continue

            if m.isAttr():
                if m.type.isAny():
                    self.membersNeedingTrace.append(m)
                    # Add a getter that doesn't need a JSContext.  Note that we
                    # don't need to do this if our originating interface is not
                    # the descriptor's interface, because in that case we
                    # wouldn't generate the getter that _does_ need a JSContext
                    # either.
                    extraMethods.append(
                        ClassMethod(
                            CGSpecializedGetterCommon.makeNativeName(descriptor, m),
                            "void",
                            [Argument("JS::MutableHandle<JS::Value>", "aRetVal")],
                            const=True,
                            body=fill(
                                """
                                JS::ExposeValueToActiveJS(${memberName});
                                aRetVal.set(${memberName});
                                """,
                                memberName=CGDictionary.makeMemberName(
                                    m.identifier.name
                                ),
                            ),
                        )
                    )
                elif m.type.isObject() or m.type.isSpiderMonkeyInterface():
                    self.membersNeedingTrace.append(m)
                elif typeNeedsRooting(m.type):
                    raise TypeError(
                        "Need to implement tracing for event member of type %s" % m.type
                    )
                elif idlTypeNeedsCycleCollection(m.type):
                    self.membersNeedingCC.append(m)

                nativeType = self.getNativeTypeForIDLType(m.type).define()
                members.append(
                    ClassMember(
                        CGDictionary.makeMemberName(m.identifier.name),
                        nativeType,
                        visibility="private",
                        body="body",
                    )
                )

        parent = self.descriptor.interface.parent
        self.parentType = self.descriptor.getDescriptor(
            parent.identifier.name
        ).nativeType.split("::")[-1]
        self.nativeType = self.descriptor.nativeType.split("::")[-1]

        if self.needCC():
            isupportsDecl = fill(
                """
                NS_DECL_ISUPPORTS_INHERITED
                NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(${nativeType}, ${parentType})
                """,
                nativeType=self.nativeType,
                parentType=self.parentType,
            )
        else:
            isupportsDecl = fill(
                """
                NS_INLINE_DECL_REFCOUNTING_INHERITED(${nativeType}, ${parentType})
                """,
                nativeType=self.nativeType,
                parentType=self.parentType,
            )

        baseDeclarations = fill(
            """
            public:
              $*{isupportsDecl}

            protected:
              virtual ~${nativeType}();
              explicit ${nativeType}(mozilla::dom::EventTarget* aOwner);

            """,
            isupportsDecl=isupportsDecl,
            nativeType=self.nativeType,
            parentType=self.parentType,
        )

        className = self.nativeType
        asConcreteTypeMethod = ClassMethod(
            "As%s" % className,
            "%s*" % className,
            [],
            virtual=True,
            body="return this;\n",
            breakAfterReturnDecl=" ",
            override=True,
        )
        extraMethods.append(asConcreteTypeMethod)

        CGClass.__init__(
            self,
            className,
            bases=[ClassBase(self.parentType)],
            methods=extraMethods + self.methodDecls,
            members=members,
            extradeclarations=baseDeclarations,
        )

    def getWrapObjectBody(self):
        return (
            "return %s_Binding::Wrap(aCx, this, aGivenProto);\n" % self.descriptor.name
        )

    def needCC(self):
        return len(self.membersNeedingCC) != 0 or len(self.membersNeedingTrace) != 0

    def implTraverse(self):
        retVal = ""
        for m in self.membersNeedingCC:
            retVal += (
                "  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(%s)\n"
                % CGDictionary.makeMemberName(m.identifier.name)
            )
        return retVal

    def implUnlink(self):
        retVal = ""
        for m in self.membersNeedingCC:
            retVal += (
                "  NS_IMPL_CYCLE_COLLECTION_UNLINK(%s)\n"
                % CGDictionary.makeMemberName(m.identifier.name)
            )
        for m in self.membersNeedingTrace:
            name = CGDictionary.makeMemberName(m.identifier.name)
            if m.type.isAny():
                retVal += "  tmp->" + name + ".setUndefined();\n"
            elif m.type.isObject() or m.type.isSpiderMonkeyInterface():
                retVal += "  tmp->" + name + " = nullptr;\n"
            else:
                raise TypeError("Unknown traceable member type %s" % m.type)
        return retVal

    def implTrace(self):
        retVal = ""
        for m in self.membersNeedingTrace:
            retVal += (
                "  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(%s)\n"
                % CGDictionary.makeMemberName(m.identifier.name)
            )
        return retVal

    def define(self):
        for m in self.membersNeedingTrace:
            if not (
                m.type.isAny() or m.type.isObject() or m.type.isSpiderMonkeyInterface()
            ):
                raise TypeError("Unknown traceable member type %s" % m.type)

        if len(self.membersNeedingTrace) > 0:
            dropJS = "mozilla::DropJSObjects(this);\n"
        else:
            dropJS = ""
        # Just override CGClass and do our own thing
        ctorParams = (
            "aOwner, nullptr, nullptr" if self.parentType == "Event" else "aOwner"
        )

        if self.needCC():
            classImpl = fill(
                """

                NS_IMPL_CYCLE_COLLECTION_CLASS(${nativeType})

                NS_IMPL_ADDREF_INHERITED(${nativeType}, ${parentType})
                NS_IMPL_RELEASE_INHERITED(${nativeType}, ${parentType})

                NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(${nativeType}, ${parentType})
                $*{traverse}
                NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

                NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(${nativeType}, ${parentType})
                $*{trace}
                NS_IMPL_CYCLE_COLLECTION_TRACE_END

                NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(${nativeType}, ${parentType})
                $*{unlink}
                NS_IMPL_CYCLE_COLLECTION_UNLINK_END

                NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(${nativeType})
                NS_INTERFACE_MAP_END_INHERITING(${parentType})
                """,
                nativeType=self.nativeType,
                parentType=self.parentType,
                traverse=self.implTraverse(),
                unlink=self.implUnlink(),
                trace=self.implTrace(),
            )
        else:
            classImpl = ""

        classImpl += fill(
            """

            ${nativeType}::${nativeType}(mozilla::dom::EventTarget* aOwner)
              : ${parentType}(${ctorParams})
            {
            }

            ${nativeType}::~${nativeType}()
            {
              $*{dropJS}
            }

            """,
            nativeType=self.nativeType,
            ctorParams=ctorParams,
            parentType=self.parentType,
            dropJS=dropJS,
        )

        return classImpl + CGBindingImplClass.define(self)

    def getNativeTypeForIDLType(self, type):
        if type.isPrimitive() and type.tag() in builtinNames:
            nativeType = CGGeneric(builtinNames[type.tag()])
            if type.nullable():
                nativeType = CGTemplatedType("Nullable", nativeType)
        elif type.isEnum():
            nativeType = CGGeneric(type.unroll().inner.identifier.name)
            if type.nullable():
                nativeType = CGTemplatedType("Nullable", nativeType)
        elif type.isJSString():
            nativeType = CGGeneric("JS::Heap<JSString*>")
        elif type.isDOMString() or type.isUSVString():
            nativeType = CGGeneric("nsString")
        elif type.isByteString() or type.isUTF8String():
            nativeType = CGGeneric("nsCString")
        elif type.isPromise():
            nativeType = CGGeneric("RefPtr<Promise>")
        elif type.isDictionary():
            if typeNeedsRooting(type):
                raise TypeError(
                    "We don't support event members that are dictionary types "
                    "that need rooting (%s)" % type
                )
            nativeType = CGGeneric(CGDictionary.makeDictionaryName(type.unroll().inner))
            if type.nullable():
                nativeType = CGTemplatedType("Nullable", nativeType)
        elif type.isGeckoInterface():
            iface = type.unroll().inner
            nativeType = self.descriptor.getDescriptor(iface.identifier.name).nativeType
            # Now trim off unnecessary namespaces
            nativeType = nativeType.split("::")
            if nativeType[0] == "mozilla":
                nativeType.pop(0)
                if nativeType[0] == "dom":
                    nativeType.pop(0)
            nativeType = CGWrapper(
                CGGeneric("::".join(nativeType)), pre="RefPtr<", post=">"
            )
        elif type.isAny():
            nativeType = CGGeneric("JS::Heap<JS::Value>")
        elif type.isObject() or type.isSpiderMonkeyInterface():
            nativeType = CGGeneric("JS::Heap<JSObject*>")
        elif type.isUnion():
            nativeType = CGGeneric(CGUnionStruct.unionTypeDecl(type, True))
        elif type.isSequence():
            if type.nullable():
                innerType = type.inner.inner
            else:
                innerType = type.inner
            if (
                not innerType.isPrimitive()
                and not innerType.isEnum()
                and not innerType.isDOMString()
                and not innerType.isByteString()
                and not innerType.isUTF8String()
                and not innerType.isPromise()
                and not innerType.isGeckoInterface()
            ):
                raise TypeError(
                    "Don't know how to properly manage GC/CC for "
                    "event member of type %s" % type
                )
            nativeType = CGTemplatedType(
                "nsTArray", self.getNativeTypeForIDLType(innerType)
            )
            if type.nullable():
                nativeType = CGTemplatedType("Nullable", nativeType)
        else:
            raise TypeError("Don't know how to declare event member of type %s" % type)
        return nativeType


class CGEventRoot(CGThing):
    def __init__(self, config, interfaceName):
        descriptor = config.getDescriptor(interfaceName)

        self.root = CGWrapper(CGEventClass(descriptor), pre="\n", post="\n")

        self.root = CGNamespace.build(["mozilla", "dom"], self.root)

        self.root = CGList(
            [CGClassForwardDeclare("JSContext", isStruct=True), self.root]
        )

        parent = descriptor.interface.parent.identifier.name

        # Throw in our #includes
        self.root = CGHeaders(
            [descriptor],
            [],
            [],
            [],
            [
                config.getDescriptor(parent).headerFile,
                "mozilla/Attributes.h",
                "mozilla/dom/%sBinding.h" % interfaceName,
                "mozilla/dom/BindingUtils.h",
            ],
            [
                "%s.h" % interfaceName,
                "js/GCAPI.h",
                "mozilla/HoldDropJSObjects.h",
                "mozilla/dom/Nullable.h",
            ],
            "",
            self.root,
            config,
        )

        # And now some include guards
        self.root = CGIncludeGuard(interfaceName, self.root)

        self.root = CGWrapper(
            self.root,
            pre=(
                AUTOGENERATED_WITH_SOURCE_WARNING_COMMENT
                % os.path.basename(descriptor.interface.filename)
            ),
        )

        self.root = CGWrapper(
            self.root,
            pre=dedent(
                """
            /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
            /* vim:set ts=2 sw=2 sts=2 et cindent: */
            /* This Source Code Form is subject to the terms of the Mozilla Public
             * License, v. 2.0. If a copy of the MPL was not distributed with this
             * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

            """
            ),
        )

    def declare(self):
        return self.root.declare()

    def define(self):
        return self.root.define()