clang-tools-extra/clangd/ExpectedTypes.cpp

   1 //===--- ExpectedTypes.cpp ---------------------------------------*- 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 #include "ExpectedTypes.h"
  10 #include "clang/AST/ASTContext.h"
  11 #include "clang/AST/DeclTemplate.h"
  12 #include "clang/AST/Type.h"
  13 #include "clang/Index/USRGeneration.h"
  14 #include "clang/Sema/CodeCompleteConsumer.h"
  15 #include <optional>
  16
  17 namespace clang {
  18 namespace clangd {
  19 namespace {
  20
  21 static const Type *toEquivClass(ASTContext &Ctx, QualType T) {
  22   if (T.isNull() || T->isDependentType())
  23     return nullptr;
  24   // Drop references, we do not handle reference inits properly anyway.
  25   T = T.getCanonicalType().getNonReferenceType();
  26   // Numeric types are the simplest case.
  27   if (T->isBooleanType())
  28     return Ctx.BoolTy.getTypePtr();
  29   if (T->isIntegerType() && !T->isEnumeralType())
  30     return Ctx.IntTy.getTypePtr(); // All integers are equivalent.
  31   if (T->isFloatingType() && !T->isComplexType())
  32     return Ctx.FloatTy.getTypePtr(); // All floats are equivalent.
  33
  34   // Do some simple transformations.
  35   if (T->isArrayType()) // Decay arrays to pointers.
  36     return Ctx.getPointerType(QualType(T->getArrayElementTypeNoTypeQual(), 0))
  37         .getTypePtr();
  38   // Drop the qualifiers and return the resulting type.
  39   // FIXME: also drop qualifiers from pointer types, e.g. 'const T* => T*'
  40   return T.getTypePtr();
  41 }
  42
  43 static std::optional<QualType> typeOfCompletion(const CodeCompletionResult &R) {
  44   const NamedDecl *D = R.Declaration;
  45   // Templates do not have a type on their own, look at the templated decl.
  46   if (auto *Template = dyn_cast_or_null<TemplateDecl>(D))
  47     D = Template->getTemplatedDecl();
  48   auto *VD = dyn_cast_or_null<ValueDecl>(D);
  49   if (!VD)
  50     return std::nullopt; // We handle only variables and functions below.
  51   auto T = VD->getType();
  52   if (T.isNull())
  53     return std::nullopt;
  54   if (auto *FuncT = T->getAs<FunctionType>()) {
  55     // Functions are a special case. They are completed as 'foo()' and we want
  56     // to match their return type rather than the function type itself.
  57     // FIXME(ibiryukov): in some cases, we might want to avoid completing `()`
  58     // after the function name, e.g. `std::cout << std::endl`.
  59     return FuncT->getReturnType();
  60   }
  61   return T;
  62 }
  63 } // namespace
  64
  65 std::optional<OpaqueType> OpaqueType::encode(ASTContext &Ctx, QualType T) {
  66   if (T.isNull())
  67     return std::nullopt;
  68   const Type *C = toEquivClass(Ctx, T);
  69   if (!C)
  70     return std::nullopt;
  71   llvm::SmallString<128> Encoded;
  72   if (index::generateUSRForType(QualType(C, 0), Ctx, Encoded))
  73     return std::nullopt;
  74   return OpaqueType(std::string(Encoded));
  75 }
  76
  77 OpaqueType::OpaqueType(std::string Data) : Data(std::move(Data)) {}
  78
  79 std::optional<OpaqueType> OpaqueType::fromType(ASTContext &Ctx, QualType Type) {
  80   return encode(Ctx, Type);
  81 }
  82
  83 std::optional<OpaqueType>
  84 OpaqueType::fromCompletionResult(ASTContext &Ctx,
  85                                  const CodeCompletionResult &R) {
  86   auto T = typeOfCompletion(R);
  87   if (!T)
  88     return std::nullopt;
  89   return encode(Ctx, *T);
  90 }
  91
  92 } // namespace clangd
  93 } // namespace clang