[clang] fix broken canonicalization of DeducedTemplateSpecializationType

clang/include/clang/AST/ASTContext.h

@@ -1771,6 +1771,13 @@ class ASTContext : public RefCountedBase<ASTContext> {
                                                 QualType DeducedType,
                                                 bool IsDependent) const;
 
+private:
+  QualType getDeducedTemplateSpecializationTypeInternal(TemplateName Template,
+                                                        QualType DeducedType,
+                                                        bool IsDependent,
+                                                        QualType Canon) const;
+
+public:
   /// Return the unique reference to the type for the specified TagDecl
   /// (struct/union/class/enum) decl.
   QualType getTagDeclType(const TagDecl *Decl) const;

clang/include/clang/AST/TemplateName.h

@@ -346,7 +346,9 @@ class TemplateName {
   /// error.
   void dump() const;
 
-  void Profile(llvm::FoldingSetNodeID &ID);
+  void Profile(llvm::FoldingSetNodeID &ID) {
+    ID.AddPointer(Storage.getOpaqueValue());
+  }
 
   /// Retrieve the template name as a void pointer.
   void *getAsVoidPointer() const { return Storage.getOpaqueValue(); }

clang/include/clang/AST/Type.h

@@ -6050,30 +6050,27 @@ class DeducedTemplateSpecializationType : public DeducedType,
 
   DeducedTemplateSpecializationType(TemplateName Template,
                                     QualType DeducedAsType,
-                                    bool IsDeducedAsDependent)
+                                    bool IsDeducedAsDependent, QualType Canon)
       : DeducedType(DeducedTemplateSpecialization, DeducedAsType,
                     toTypeDependence(Template.getDependence()) |
                         (IsDeducedAsDependent
                              ? TypeDependence::DependentInstantiation
                              : TypeDependence::None),
-                    DeducedAsType.isNull() ? QualType(this, 0)
-                                           : DeducedAsType.getCanonicalType()),
+                    Canon),
         Template(Template) {}
 
 public:
   /// Retrieve the name of the template that we are deducing.
   TemplateName getTemplateName() const { return Template;}
 
-  void Profile(llvm::FoldingSetNodeID &ID) {
+  void Profile(llvm::FoldingSetNodeID &ID) const {
     Profile(ID, getTemplateName(), getDeducedType(), isDependentType());
   }
 
   static void Profile(llvm::FoldingSetNodeID &ID, TemplateName Template,
                       QualType Deduced, bool IsDependent) {
     Template.Profile(ID);
-    QualType CanonicalType =
-        Deduced.isNull() ? Deduced : Deduced.getCanonicalType();
-    ID.AddPointer(CanonicalType.getAsOpaquePtr());
+    Deduced.Profile(ID);
     ID.AddBoolean(IsDependent || Template.isDependent());
   }
 

clang/lib/AST/ASTContext.cpp

@@ -5925,11 +5925,9 @@ QualType ASTContext::getUnconstrainedType(QualType T) const {
   return T;
 }
 
-/// Return the uniqued reference to the deduced template specialization type
-/// which has been deduced to the given type, or to the canonical undeduced
-/// such type, or the canonical deduced-but-dependent such type.
-QualType ASTContext::getDeducedTemplateSpecializationType(
-    TemplateName Template, QualType DeducedType, bool IsDependent) const {
+QualType ASTContext::getDeducedTemplateSpecializationTypeInternal(
+    TemplateName Template, QualType DeducedType, bool IsDependent,
+    QualType Canon) const {
   // Look in the folding set for an existing type.
   void *InsertPos = nullptr;
   llvm::FoldingSetNodeID ID;
@@ -5940,7 +5938,8 @@ QualType ASTContext::getDeducedTemplateSpecializationType(
     return QualType(DTST, 0);
 
   auto *DTST = new (*this, alignof(DeducedTemplateSpecializationType))
-      DeducedTemplateSpecializationType(Template, DeducedType, IsDependent);
+      DeducedTemplateSpecializationType(Template, DeducedType, IsDependent,
+                                        Canon);
   llvm::FoldingSetNodeID TempID;
   DTST->Profile(TempID);
   assert(ID == TempID && "ID does not match");
@@ -5949,6 +5948,20 @@ QualType ASTContext::getDeducedTemplateSpecializationType(
   return QualType(DTST, 0);
 }
 
+/// Return the uniqued reference to the deduced template specialization type
+/// which has been deduced to the given type, or to the canonical undeduced
+/// such type, or the canonical deduced-but-dependent such type.
+QualType ASTContext::getDeducedTemplateSpecializationType(
+    TemplateName Template, QualType DeducedType, bool IsDependent) const {
+  QualType Canon = DeducedType.isNull()
+                       ? getDeducedTemplateSpecializationTypeInternal(
+                             getCanonicalTemplateName(Template), QualType(),
+                             IsDependent, QualType())
+                       : DeducedType.getCanonicalType();
+  return getDeducedTemplateSpecializationTypeInternal(Template, DeducedType,
+                                                      IsDependent, Canon);
+}
+
 /// getAtomicType - Return the uniqued reference to the atomic type for
 /// the given value type.
 QualType ASTContext::getAtomicType(QualType T) const {

clang/lib/AST/TemplateName.cpp

@@ -264,15 +264,6 @@ bool TemplateName::containsUnexpandedParameterPack() const {
   return getDependence() & TemplateNameDependence::UnexpandedPack;
 }
 
-void TemplateName::Profile(llvm::FoldingSetNodeID &ID) {
-  if (const auto* USD = getAsUsingShadowDecl())
-    ID.AddPointer(USD->getCanonicalDecl());
-  else if (const auto *TD = getAsTemplateDecl())
-    ID.AddPointer(TD->getCanonicalDecl());
-  else
-    ID.AddPointer(Storage.getOpaqueValue());
-}
-
 void TemplateName::print(raw_ostream &OS, const PrintingPolicy &Policy,
                          Qualified Qual) const {
   auto handleAnonymousTTP = [](TemplateDecl *TD, raw_ostream &OS) {

clang/unittests/AST/CMakeLists.txt

@@ -31,6 +31,7 @@ add_clang_unittest(ASTTests
   EvaluateAsRValueTest.cpp
   ExternalASTSourceTest.cpp
   NamedDeclPrinterTest.cpp
+  ProfilingTest.cpp
   RandstructTest.cpp
   RecursiveASTVisitorTest.cpp
   SizelessTypesTest.cpp

clang/unittests/AST/ProfilingTest.cpp

@@ -0,0 +1,73 @@
+//===- unittests/AST/ProfilingTest.cpp --- Tests for Profiling ------===//
+//
+// 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 "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Tooling/Tooling.h"
+#include "gtest/gtest.h"
+#include <utility>
+
+namespace clang {
+namespace {
+using namespace ast_matchers;
+
+static auto getClassTemplateRedecls() {
+  std::string Code = R"cpp(
+    template <class> struct A;
+    template <class> struct A;
+    template <class> struct A;
+  )cpp";
+  auto AST = tooling::buildASTFromCode(Code);
+  ASTContext &Ctx = AST->getASTContext();
+
+  auto MatchResults = match(classTemplateDecl().bind("id"), Ctx);
+  SmallVector<ClassTemplateDecl *, 3> Res;
+  for (BoundNodes &N : MatchResults) {
+    if (auto *CTD = const_cast<ClassTemplateDecl *>(
+            N.getNodeAs<ClassTemplateDecl>("id")))
+      Res.push_back(CTD);
+  }
+  assert(Res.size() == 3);
+  for (auto &&I : Res)
+    assert(I->getCanonicalDecl() == Res[0]);
+  return std::make_tuple(std::move(AST), Res[1], Res[2]);
+}
+
+template <class T> static void testTypeNode(const T *T1, const T *T2) {
+  {
+    llvm::FoldingSetNodeID ID1, ID2;
+    T1->Profile(ID1);
+    T2->Profile(ID2);
+    ASSERT_NE(ID1, ID2);
+  }
+  auto *CT1 = cast<T>(T1->getCanonicalTypeInternal());
+  auto *CT2 = cast<T>(T2->getCanonicalTypeInternal());
+  {
+    llvm::FoldingSetNodeID ID1, ID2;
+    CT1->Profile(ID1);
+    CT2->Profile(ID2);
+    ASSERT_EQ(ID1, ID2);
+  }
+}
+
+TEST(Profiling, DeducedTemplateSpecializationType_Name) {
+  auto [AST, CTD1, CTD2] = getClassTemplateRedecls();
+  ASTContext &Ctx = AST->getASTContext();
+
+  auto *T1 = cast<DeducedTemplateSpecializationType>(
+      Ctx.getDeducedTemplateSpecializationType(TemplateName(CTD1), QualType(),
+                                               false));
+  auto *T2 = cast<DeducedTemplateSpecializationType>(
+      Ctx.getDeducedTemplateSpecializationType(TemplateName(CTD2), QualType(),
+                                               false));
+  testTypeNode(T1, T2);
+}
+
+} // namespace
+} // namespace clang