clang-tools-extra/clangd/FindTarget.h

   1 //===--- FindTarget.h - What does an AST node refer to? ---------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Many clangd features are concerned with references in the AST:
  10 //  - xrefs, go-to-definition, explicitly talk about references
  11 //  - hover and code actions relate to things you "target" in the editor
  12 //  - refactoring actions need to know about entities that are referenced
  13 //    to determine whether/how the edit can be applied.
  14 //
  15 // Historically, we have used libIndex (IndexDataConsumer) to tie source
  16 // locations to referenced declarations. This file defines a more decoupled
  17 // approach based around AST nodes (DynTypedNode), and can be combined with
  18 // SelectionTree or other traversals.
  19 //
  20 //===----------------------------------------------------------------------===//
  21
  22 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FINDTARGET_H
  23 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FINDTARGET_H
  24
  25 #include "clang/AST/ASTContext.h"
  26 #include "clang/AST/ASTTypeTraits.h"
  27 #include "clang/AST/NestedNameSpecifier.h"
  28 #include "clang/AST/Stmt.h"
  29 #include "clang/Basic/SourceLocation.h"
  30 #include "llvm/ADT/SmallVector.h"
  31 #include "llvm/Support/raw_ostream.h"
  32
  33 #include <bitset>
  34
  35 namespace clang {
  36 namespace clangd {
  37 class HeuristicResolver;
  38
  39 /// Describes the link between an AST node and a Decl it refers to.
  40 enum class DeclRelation : unsigned;
  41 /// A bitfield of DeclRelations.
  42 class DeclRelationSet;
  43
  44 /// targetDecl() finds the declaration referred to by an AST node.
  45 /// For example a RecordTypeLoc refers to the RecordDecl for the type.
  46 ///
  47 /// In some cases there are multiple results, e.g. a dependent unresolved
  48 /// OverloadExpr may have several candidates. All will be returned:
  49 ///
  50 ///    void foo(int);    <-- candidate
  51 ///    void foo(double); <-- candidate
  52 ///    template <typename T> callFoo() { foo(T()); }
  53 ///                                      ^ OverloadExpr
  54 ///
  55 /// In other cases, there may be choices about what "referred to" means.
  56 /// e.g. does naming a typedef refer to the underlying type?
  57 /// The results are marked with a set of DeclRelations, and can be filtered.
  58 ///
  59 ///    struct S{};    <-- candidate (underlying)
  60 ///    using T = S{}; <-- candidate (alias)
  61 ///    T x;
  62 ///    ^ TypedefTypeLoc
  63 ///
  64 /// Formally, we walk a graph starting at the provided node, and return the
  65 /// decls that were found. Certain edges in the graph have labels, and for each
  66 /// decl we return the set of labels seen on a path to the decl.
  67 /// For the previous example:
  68 ///
  69 ///                TypedefTypeLoc T
  70 ///                       |
  71 ///                 TypedefType T
  72 ///                    /     \
  73 ///           [underlying]  [alias]
  74 ///                  /         \
  75 ///          RecordDecl S    TypeAliasDecl T
  76 ///
  77 /// Note that this function only returns NamedDecls. Generally other decls
  78 /// don't have references in this sense, just the node itself.
  79 /// If callers want to support such decls, they should cast the node directly.
  80 ///
  81 /// FIXME: some AST nodes cannot be DynTypedNodes, these cannot be specified.
  82 llvm::SmallVector<const NamedDecl *, 1>
  83 targetDecl(const DynTypedNode &, DeclRelationSet Mask,
  84            const HeuristicResolver *Resolver);
  85
  86 /// Similar to targetDecl(), however instead of applying a filter, all possible
  87 /// decls are returned along with their DeclRelationSets.
  88 /// This is suitable for indexing, where everything is recorded and filtering
  89 /// is applied later.
  90 llvm::SmallVector<std::pair<const NamedDecl *, DeclRelationSet>, 1>
  91 allTargetDecls(const DynTypedNode &, const HeuristicResolver *);
  92
  93 enum class DeclRelation : unsigned {
  94   // Template options apply when the declaration is an instantiated template.
  95   // e.g. [[vector<int>]] vec;
  96
  97   /// This is the template instantiation that was referred to.
  98   /// e.g. template<> class vector<int> (the implicit specialization)
  99   TemplateInstantiation,
 100   /// This is the pattern the template specialization was instantiated from.
 101   /// e.g. class vector<T> (the pattern within the primary template)
 102   TemplatePattern,
 103
 104   // Alias options apply when the declaration is an alias.
 105   // e.g. namespace client { [[X]] x; }
 106
 107   /// This declaration is an alias that was referred to.
 108   /// e.g. using ns::X (the UsingDecl directly referenced),
 109   ///      using Z = ns::Y (the TypeAliasDecl directly referenced)
 110   Alias,
 111   /// This is the underlying declaration for a renaming-alias, decltype etc.
 112   /// e.g. class ns::Y (the underlying declaration referenced).
 113   ///
 114   /// Note that we don't treat `using ns::X` as a first-class declaration like
 115   /// `using Z = ns::Y`. Therefore reference to X that goes through this
 116   /// using-decl is considered a direct reference (without the Underlying bit).
 117   /// Nevertheless, we report `using ns::X` as an Alias, so that some features
 118   /// like go-to-definition can still target it.
 119   Underlying,
 120 };
 121 llvm::raw_ostream &operator<<(llvm::raw_ostream &, DeclRelation);
 122
 123 /// Information about a reference written in the source code, independent of the
 124 /// actual AST node that this reference lives in.
 125 /// Useful for tools that are source-aware, e.g. refactorings.
 126 struct ReferenceLoc {
 127   /// Contains qualifier written in the code, if any, e.g. 'ns::' for 'ns::foo'.
 128   NestedNameSpecifierLoc Qualifier;
 129   /// Start location of the last name part, i.e. 'foo' in 'ns::foo<int>'.
 130   SourceLocation NameLoc;
 131   /// True if the reference is a declaration or definition;
 132   bool IsDecl = false;
 133   // FIXME: add info about template arguments.
 134   /// A list of targets referenced by this name. Normally this has a single
 135   /// element, but multiple is also possible, e.g. in case of using declarations
 136   /// or unresolved overloaded functions.
 137   /// For dependent and unresolved references, Targets can also be empty.
 138   llvm::SmallVector<const NamedDecl *, 1> Targets;
 139 };
 140 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, ReferenceLoc R);
 141
 142 /// Recursively traverse \p S and report all references explicitly written in
 143 /// the code. The main use-case is refactorings that need to process all
 144 /// references in some subrange of the file and apply simple edits, e.g. add
 145 /// qualifiers.
 146 /// FIXME: currently this does not report references to overloaded operators.
 147 /// FIXME: extend to report location information about declaration names too.
 148 void findExplicitReferences(const Stmt *S,
 149                             llvm::function_ref<void(ReferenceLoc)> Out,
 150                             const HeuristicResolver *Resolver);
 151 void findExplicitReferences(const Decl *D,
 152                             llvm::function_ref<void(ReferenceLoc)> Out,
 153                             const HeuristicResolver *Resolver);
 154 void findExplicitReferences(const ASTContext &AST,
 155                             llvm::function_ref<void(ReferenceLoc)> Out,
 156                             const HeuristicResolver *Resolver);
 157
 158 /// Find declarations explicitly referenced in the source code defined by \p N.
 159 /// For templates, will prefer to return a template instantiation whenever
 160 /// possible. However, can also return a template pattern if the specialization
 161 /// cannot be picked, e.g. in dependent code or when there is no corresponding
 162 /// Decl for a template instantiation, e.g. for templated using decls:
 163 ///    template <class T> using Ptr = T*;
 164 ///    Ptr<int> x;
 165 ///    ^~~ there is no Decl for 'Ptr<int>', so we return the template pattern.
 166 /// \p Mask should not contain TemplatePattern or TemplateInstantiation.
 167 llvm::SmallVector<const NamedDecl *, 1>
 168 explicitReferenceTargets(DynTypedNode N, DeclRelationSet Mask,
 169                          const HeuristicResolver *Resolver);
 170
 171 // Boring implementation details of bitfield.
 172
 173 class DeclRelationSet {
 174   using Set = std::bitset<static_cast<unsigned>(DeclRelation::Underlying) + 1>;
 175   Set S;
 176   DeclRelationSet(Set S) : S(S) {}
 177
 178 public:
 179   DeclRelationSet() = default;
 180   DeclRelationSet(DeclRelation R) { S.set(static_cast<unsigned>(R)); }
 181
 182   explicit operator bool() const { return S.any(); }
 183   friend DeclRelationSet operator&(DeclRelationSet L, DeclRelationSet R) {
 184     return L.S & R.S;
 185   }
 186   friend DeclRelationSet operator|(DeclRelationSet L, DeclRelationSet R) {
 187     return L.S | R.S;
 188   }
 189   friend bool operator==(DeclRelationSet L, DeclRelationSet R) {
 190     return L.S == R.S;
 191   }
 192   friend DeclRelationSet operator~(DeclRelationSet R) { return ~R.S; }
 193   DeclRelationSet &operator|=(DeclRelationSet Other) {
 194     S |= Other.S;
 195     return *this;
 196   }
 197   DeclRelationSet &operator&=(DeclRelationSet Other) {
 198     S &= Other.S;
 199     return *this;
 200   }
 201   bool contains(DeclRelationSet Other) const {
 202     return (S & Other.S) == Other.S;
 203   }
 204   friend llvm::raw_ostream &operator<<(llvm::raw_ostream &, DeclRelationSet);
 205 };
 206 // The above operators can't be looked up if both sides are enums.
 207 // over.match.oper.html#3.2
 208 inline DeclRelationSet operator|(DeclRelation L, DeclRelation R) {
 209   return DeclRelationSet(L) | DeclRelationSet(R);
 210 }
 211 inline DeclRelationSet operator&(DeclRelation L, DeclRelation R) {
 212   return DeclRelationSet(L) & DeclRelationSet(R);
 213 }
 214 inline DeclRelationSet operator~(DeclRelation R) { return ~DeclRelationSet(R); }
 215 llvm::raw_ostream &operator<<(llvm::raw_ostream &, DeclRelationSet);
 216
 217 } // namespace clangd
 218 } // namespace clang
 219
 220 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_FINDTARGET_H