[clangd] Compute expected type for templates

clangd/ExpectedTypes.cpp

 //===--- ExpectedTypes.cpp ---------------------------------------*- C++-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "ExpectedTypes.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Type.h"
 #include "clang/Index/USRGeneration.h"
 #include "clang/Sema/CodeCompleteConsumer.h"
+#include "llvm/ADT/None.h"
 #include "llvm/ADT/STLExtras.h"
 
 namespace clang {
 namespace clangd {
 namespace {
 
 static const Type *toEquivClass(ASTContext &Ctx, QualType T) {
   if (T.isNull() || T->isDependentType())
return Ctx.getPointerType(QualType(T->getArrayElementTypeNoTypeQual(), 0))
         .getTypePtr();
   // Drop the qualifiers and return the resulting type.
   // FIXME: also drop qualifiers from pointer types, e.g. 'const T* => T*'
   return T.getTypePtr();
 }
 
 static llvm::Optional<QualType>
 typeOfCompletion(const CodeCompletionResult &R) {
-  auto *VD = dyn_cast_or_null<ValueDecl>(R.Declaration);
+  const NamedDecl *D = R.Declaration;
+  if (!D)
+    return llvm::None;
+  // Templates do not have a type on their own, look at the templated decl.
+  if (auto *Template = dyn_cast<TemplateDecl>(D))
+    D = Template->getTemplatedDecl();
+  auto *VD = dyn_cast<ValueDecl>(D);
   if (!VD)
     return llvm::None; // We handle only variables and functions below.
   auto T = VD->getType();
   if (T.isNull())
     return llvm::None;
   if (auto FuncT = T->getAs<FunctionType>()) {
     // Functions are a special case. They are completed as 'foo()' and we want
     // to match their return type rather than the function type itself.

clangd/unittests/ExpectedTypeTest.cpp

 //===-- ExpectedTypeTest.cpp  -----------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "ClangdUnit.h"
 #include "ExpectedTypes.h"
 #include "TestTU.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
+#include "llvm/ADT/None.h"
 #include "llvm/ADT/StringRef.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
 namespace clang {
 namespace clangd {
 namespace {
 
 using ::testing::Field;
 using ::testing::Matcher;
 using ::testing::SizeIs;
 using ::testing::UnorderedElementsAreArray;
 
 class ExpectedTypeConversionTest : public ::testing::Test {
 protected:
   void build(llvm::StringRef Code) {
     assert(!AST && "AST built twice");
     AST = TestTU::withCode(Code).build();
   }
 
-  const ValueDecl *decl(llvm::StringRef Name) {
-    return &cast<ValueDecl>(findDecl(*AST, Name));
-  }
+  const NamedDecl *decl(llvm::StringRef Name) { return &findDecl(*AST, Name); }
 
   QualType typeOf(llvm::StringRef Name) {
-    return decl(Name)->getType().getCanonicalType();
+    return cast<ValueDecl>(decl(Name))->getType().getCanonicalType();
   }
 
   /// An overload for convenience.
-  llvm::Optional<OpaqueType> fromCompletionResult(const ValueDecl *D) {
+  llvm::Optional<OpaqueType> fromCompletionResult(const NamedDecl *D) {
     return OpaqueType::fromCompletionResult(
         ASTCtx(), CodeCompletionResult(D, CCP_Declaration));
   }
 
   /// A set of DeclNames whose type match each other computed by
   /// OpaqueType::fromCompletionResult.
   using EquivClass = std::set<std::string>;
 
TEST_F(ExpectedTypeConversionTest, FunctionReturns) {
 
   OpaqueType IntTy = *OpaqueType::fromType(ASTCtx(), typeOf("int_"));
   EXPECT_EQ(fromCompletionResult(decl("returns_int")), IntTy);
 
   OpaqueType IntPtrTy = *OpaqueType::fromType(ASTCtx(), typeOf("int_ptr"));
   EXPECT_EQ(fromCompletionResult(decl("returns_ptr")), IntPtrTy);
 }
 
+TEST_F(ExpectedTypeConversionTest, Templates) {
+  build(R"cpp(
+template <class T>
+int* returns_not_dependent();
+template <class T>
+T* returns_dependent();
+
+template <class T>
+int* var_not_dependent = nullptr;
+template <class T>
+T* var_dependent = nullptr;
+
+int* int_ptr_;
+  )cpp");
+
+  auto IntPtrTy = *OpaqueType::fromType(ASTCtx(), typeOf("int_ptr_"));
+  EXPECT_EQ(fromCompletionResult(decl("returns_not_dependent")), IntPtrTy);
+  EXPECT_EQ(fromCompletionResult(decl("returns_dependent")), llvm::None);
+
+  EXPECT_EQ(fromCompletionResult(decl("var_not_dependent")), IntPtrTy);
+  EXPECT_EQ(fromCompletionResult(decl("var_dependent")), llvm::None);
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang