[clang-tools-extra] [clang] remove ClassScopeFunctionSpecializationDecl (PR #66636)

Krystian Stasiowski via cfe-commits cfe-commits at lists.llvm.org
Tue Sep 19 02:21:22 PDT 2023


https://github.com/sdkrystian updated https://github.com/llvm/llvm-project/pull/66636

>From d11d546f3190936ba45c57b4825073026d817878 Mon Sep 17 00:00:00 2001
From: Krystian Stasiowski <sdkrystian at gmail.com>
Date: Fri, 25 Aug 2023 14:07:32 -0400
Subject: [PATCH 1/2] [clang] remove ClassScopeFunctionSpecializationDecl

---
 .../clang-tidy/modernize/UseEmplaceCheck.cpp  |   2 +-
 .../clangd/SemanticHighlighting.cpp           |   9 --
 clang/include/clang/AST/ASTNodeTraverser.h    |   7 +-
 clang/include/clang/AST/Decl.h                |  10 +-
 clang/include/clang/AST/DeclTemplate.h        | 150 +++---------------
 clang/include/clang/AST/RecursiveASTVisitor.h |  19 ++-
 clang/include/clang/Basic/DeclNodes.td        |   1 -
 .../clang/Basic/DiagnosticSemaKinds.td        |   8 +-
 clang/include/clang/Sema/Sema.h               |   6 +-
 clang/include/clang/Sema/Template.h           |   2 -
 .../include/clang/Serialization/ASTBitCodes.h |   4 -
 .../clang/Serialization/ASTRecordReader.h     |   2 +
 clang/lib/AST/ASTImporter.cpp                 |  26 ++-
 clang/lib/AST/Decl.cpp                        |  71 ++++++---
 clang/lib/AST/DeclBase.cpp                    |   2 -
 clang/lib/AST/DeclTemplate.cpp                |  13 --
 clang/lib/AST/ODRHash.cpp                     |   4 +
 clang/lib/CodeGen/CGDecl.cpp                  |   1 -
 clang/lib/Index/IndexSymbol.cpp               |   1 -
 clang/lib/Sema/SemaDecl.cpp                   | 112 ++++++-------
 clang/lib/Sema/SemaTemplate.cpp               |  14 +-
 .../lib/Sema/SemaTemplateInstantiateDecl.cpp  | 121 +++++++-------
 clang/lib/Serialization/ASTCommon.cpp         |   1 -
 clang/lib/Serialization/ASTReader.cpp         |  19 ++-
 clang/lib/Serialization/ASTReaderDecl.cpp     |  59 ++-----
 clang/lib/Serialization/ASTWriter.cpp         |   1 -
 clang/lib/Serialization/ASTWriterDecl.cpp     |  42 ++---
 .../Checkers/SmartPtrModeling.cpp             |   2 +-
 clang/test/AST/ast-dump-decl.cpp              |   9 +-
 clang/test/CXX/drs/dr7xx.cpp                  |   5 +
 .../test/SemaTemplate/instantiate-method.cpp  |   7 +-
 clang/tools/libclang/CIndex.cpp               |   1 -
 32 files changed, 290 insertions(+), 441 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
index 554abcd900e329c..06ae1f4e257528f 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
@@ -67,7 +67,7 @@ AST_MATCHER_P(CallExpr, hasLastArgument,
 // function had parameters defined (this is useful to check if there is only one
 // variadic argument).
 AST_MATCHER(CXXMemberCallExpr, hasSameNumArgsAsDeclNumParams) {
-  if (Node.getMethodDecl()->isFunctionTemplateSpecialization())
+  if (Node.getMethodDecl()->getPrimaryTemplate())
     return Node.getNumArgs() == Node.getMethodDecl()
                                     ->getPrimaryTemplate()
                                     ->getTemplatedDecl()
diff --git a/clang-tools-extra/clangd/SemanticHighlighting.cpp b/clang-tools-extra/clangd/SemanticHighlighting.cpp
index 45c01634e2e38d1..7649e37e1f96663 100644
--- a/clang-tools-extra/clangd/SemanticHighlighting.cpp
+++ b/clang-tools-extra/clangd/SemanticHighlighting.cpp
@@ -715,13 +715,6 @@ class CollectExtraHighlightings
     return true;
   }
 
-  bool VisitClassScopeFunctionSpecializationDecl(
-      ClassScopeFunctionSpecializationDecl *D) {
-    if (auto *Args = D->getTemplateArgsAsWritten())
-      H.addAngleBracketTokens(Args->getLAngleLoc(), Args->getRAngleLoc());
-    return true;
-  }
-
   bool VisitDeclRefExpr(DeclRefExpr *E) {
     H.addAngleBracketTokens(E->getLAngleLoc(), E->getRAngleLoc());
     return true;
@@ -752,8 +745,6 @@ class CollectExtraHighlightings
     }
     if (auto *Args = D->getTemplateSpecializationArgsAsWritten())
       H.addAngleBracketTokens(Args->getLAngleLoc(), Args->getRAngleLoc());
-    if (auto *I = D->getDependentSpecializationInfo())
-      H.addAngleBracketTokens(I->getLAngleLoc(), I->getRAngleLoc());
     return true;
   }
 
diff --git a/clang/include/clang/AST/ASTNodeTraverser.h b/clang/include/clang/AST/ASTNodeTraverser.h
index 1151a756ff377b6..c3d233d3ab4a259 100644
--- a/clang/include/clang/AST/ASTNodeTraverser.h
+++ b/clang/include/clang/AST/ASTNodeTraverser.h
@@ -428,6 +428,8 @@ class ASTNodeTraverser
   void VisitFunctionDecl(const FunctionDecl *D) {
     if (const auto *FTSI = D->getTemplateSpecializationInfo())
       dumpTemplateArgumentList(*FTSI->TemplateArguments);
+    else if (const auto *DFTSI = D->getDependentSpecializationInfo())
+      dumpASTTemplateArgumentListInfo(DFTSI->TemplateArgumentsAsWritten);
 
     if (D->param_begin())
       for (const auto *Parameter : D->parameters())
@@ -578,11 +580,6 @@ class ASTNodeTraverser
     dumpTemplateParameters(D->getTemplateParameters());
   }
 
-  void VisitClassScopeFunctionSpecializationDecl(
-      const ClassScopeFunctionSpecializationDecl *D) {
-    Visit(D->getSpecialization());
-    dumpASTTemplateArgumentListInfo(D->getTemplateArgsAsWritten());
-  }
   void VisitVarTemplateDecl(const VarTemplateDecl *D) { dumpTemplateDecl(D); }
 
   void VisitBuiltinTemplateDecl(const BuiltinTemplateDecl *D) {
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index c51b33c9e594a81..3d0f144d2337c6b 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -2813,9 +2813,7 @@ class FunctionDecl : public DeclaratorDecl,
 
   /// Determine whether this function is a function template
   /// specialization.
-  bool isFunctionTemplateSpecialization() const {
-    return getPrimaryTemplate() != nullptr;
-  }
+  bool isFunctionTemplateSpecialization() const;
 
   /// If this function is actually a function template specialization,
   /// retrieve information about this function template specialization.
@@ -2898,9 +2896,9 @@ class FunctionDecl : public DeclaratorDecl,
 
   /// Specifies that this function declaration is actually a
   /// dependent function template specialization.
-  void setDependentTemplateSpecialization(ASTContext &Context,
-                             const UnresolvedSetImpl &Templates,
-                      const TemplateArgumentListInfo &TemplateArgs);
+  void setDependentTemplateSpecialization(
+      ASTContext &Context, const UnresolvedSetImpl &Templates,
+      const TemplateArgumentListInfo *TemplateArgs);
 
   DependentFunctionTemplateSpecializationInfo *
   getDependentSpecializationInfo() const;
diff --git a/clang/include/clang/AST/DeclTemplate.h b/clang/include/clang/AST/DeclTemplate.h
index 6264f15d6ffb961..54d28227a4ae91b 100644
--- a/clang/include/clang/AST/DeclTemplate.h
+++ b/clang/include/clang/AST/DeclTemplate.h
@@ -583,7 +583,7 @@ class FunctionTemplateSpecializationInfo final
   /// \code
   /// template<typename> struct A {
   ///   template<typename> void f();
-  ///   template<> void f<int>(); // ClassScopeFunctionSpecializationDecl
+  ///   template<> void f<int>();
   /// };
   /// \endcode
   ///
@@ -682,82 +682,48 @@ class MemberSpecializationInfo {
 /// Provides information about a dependent function-template
 /// specialization declaration.
 ///
-/// Since explicit function template specialization and instantiation
-/// declarations can only appear in namespace scope, and you can only
-/// specialize a member of a fully-specialized class, the only way to
-/// get one of these is in a friend declaration like the following:
+/// This is used for function templates explicit specializations declared
+/// within class templates:
+///
+/// \code
+/// template<typename> struct A {
+///   template<typename> void f();
+///   template<> void f<int>(); // DependentFunctionTemplateSpecializationInfo
+/// };
+/// \endcode
+///
+/// As well as dependent friend declarations naming function template
+/// specializations declared within class templates:
 ///
 /// \code
 ///   template \<class T> void foo(T);
 ///   template \<class T> class A {
-///     friend void foo<>(T);
+///     friend void foo<>(T); // DependentFunctionTemplateSpecializationInfo
 ///   };
 /// \endcode
 class DependentFunctionTemplateSpecializationInfo final
     : private llvm::TrailingObjects<DependentFunctionTemplateSpecializationInfo,
-                                    TemplateArgumentLoc,
                                     FunctionTemplateDecl *> {
-  /// The number of potential template candidates.
-  unsigned NumTemplates;
-
-  /// The number of template arguments.
-  unsigned NumArgs;
-
-  /// The locations of the left and right angle brackets.
-  SourceRange AngleLocs;
+  friend TrailingObjects;
 
-  size_t numTrailingObjects(OverloadToken<TemplateArgumentLoc>) const {
-    return NumArgs;
-  }
-  size_t numTrailingObjects(OverloadToken<FunctionTemplateDecl *>) const {
-    return NumTemplates;
-  }
+  /// The number of candidates for the primary template.
+  unsigned NumCandidates;
 
   DependentFunctionTemplateSpecializationInfo(
-                                 const UnresolvedSetImpl &Templates,
-                                 const TemplateArgumentListInfo &TemplateArgs);
+      const UnresolvedSetImpl &Candidates,
+      const ASTTemplateArgumentListInfo *TemplateArgsWritten);
 
 public:
-  friend TrailingObjects;
+  /// The template arguments as written in the sources, if provided.
+  const ASTTemplateArgumentListInfo *TemplateArgumentsAsWritten;
 
   static DependentFunctionTemplateSpecializationInfo *
-  Create(ASTContext &Context, const UnresolvedSetImpl &Templates,
-         const TemplateArgumentListInfo &TemplateArgs);
-
-  /// Returns the number of function templates that this might
-  /// be a specialization of.
-  unsigned getNumTemplates() const { return NumTemplates; }
+  Create(ASTContext &Context, const UnresolvedSetImpl &Candidates,
+         const TemplateArgumentListInfo *TemplateArgs);
 
-  /// Returns the i'th template candidate.
-  FunctionTemplateDecl *getTemplate(unsigned I) const {
-    assert(I < getNumTemplates() && "template index out of range");
-    return getTrailingObjects<FunctionTemplateDecl *>()[I];
-  }
-
-  /// Returns the explicit template arguments that were given.
-  const TemplateArgumentLoc *getTemplateArgs() const {
-    return getTrailingObjects<TemplateArgumentLoc>();
-  }
-
-  /// Returns the number of explicit template arguments that were given.
-  unsigned getNumTemplateArgs() const { return NumArgs; }
-
-  llvm::ArrayRef<TemplateArgumentLoc> arguments() const {
-    return llvm::ArrayRef(getTemplateArgs(), getNumTemplateArgs());
-  }
-
-  /// Returns the nth template argument.
-  const TemplateArgumentLoc &getTemplateArg(unsigned I) const {
-    assert(I < getNumTemplateArgs() && "template arg index out of range");
-    return getTemplateArgs()[I];
-  }
-
-  SourceLocation getLAngleLoc() const {
-    return AngleLocs.getBegin();
-  }
-
-  SourceLocation getRAngleLoc() const {
-    return AngleLocs.getEnd();
+  /// Returns the candidates for the primary function template.
+  ArrayRef<FunctionTemplateDecl *> getCandidates() const {
+    return {getTrailingObjects<FunctionTemplateDecl *>(), NumCandidates};
   }
 };
 
@@ -2613,70 +2579,6 @@ class TypeAliasTemplateDecl : public RedeclarableTemplateDecl {
   static bool classofKind(Kind K) { return K == TypeAliasTemplate; }
 };
 
-/// Declaration of a function specialization at template class scope.
-///
-/// For example:
-/// \code
-/// template <class T>
-/// class A {
-///    template <class U> void foo(U a) { }
-///    template<> void foo(int a) { }
-/// }
-/// \endcode
-///
-/// "template<> foo(int a)" will be saved in Specialization as a normal
-/// CXXMethodDecl. Then during an instantiation of class A, it will be
-/// transformed into an actual function specialization.
-///
-/// FIXME: This is redundant; we could store the same information directly on
-/// the CXXMethodDecl as a DependentFunctionTemplateSpecializationInfo.
-class ClassScopeFunctionSpecializationDecl : public Decl {
-  CXXMethodDecl *Specialization;
-  const ASTTemplateArgumentListInfo *TemplateArgs;
-
-  ClassScopeFunctionSpecializationDecl(
-      DeclContext *DC, SourceLocation Loc, CXXMethodDecl *FD,
-      const ASTTemplateArgumentListInfo *TemplArgs)
-      : Decl(Decl::ClassScopeFunctionSpecialization, DC, Loc),
-        Specialization(FD), TemplateArgs(TemplArgs) {}
-
-  ClassScopeFunctionSpecializationDecl(EmptyShell Empty)
-      : Decl(Decl::ClassScopeFunctionSpecialization, Empty) {}
-
-  virtual void anchor();
-
-public:
-  friend class ASTDeclReader;
-  friend class ASTDeclWriter;
-
-  CXXMethodDecl *getSpecialization() const { return Specialization; }
-  bool hasExplicitTemplateArgs() const { return TemplateArgs; }
-  const ASTTemplateArgumentListInfo *getTemplateArgsAsWritten() const {
-    return TemplateArgs;
-  }
-
-  static ClassScopeFunctionSpecializationDecl *
-  Create(ASTContext &C, DeclContext *DC, SourceLocation Loc, CXXMethodDecl *FD,
-         bool HasExplicitTemplateArgs,
-         const TemplateArgumentListInfo &TemplateArgs) {
-    return new (C, DC) ClassScopeFunctionSpecializationDecl(
-        DC, Loc, FD,
-        HasExplicitTemplateArgs
-            ? ASTTemplateArgumentListInfo::Create(C, TemplateArgs)
-            : nullptr);
-  }
-
-  static ClassScopeFunctionSpecializationDecl *
-  CreateDeserialized(ASTContext &Context, unsigned ID);
-
-  // Implement isa/cast/dyncast/etc.
-  static bool classof(const Decl *D) { return classofKind(D->getKind()); }
-
-  static bool classofKind(Kind K) {
-    return K == Decl::ClassScopeFunctionSpecialization;
-  }
-};
-
 /// Represents a variable template specialization, which refers to
 /// a variable template with a given set of template arguments.
 ///
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
index d4146d52893ffb1..70fe4ac273ae57c 100644
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -1563,16 +1563,6 @@ DEF_TRAVERSE_DECL(FriendTemplateDecl, {
   }
 })
 
-DEF_TRAVERSE_DECL(ClassScopeFunctionSpecializationDecl, {
-  TRY_TO(TraverseDecl(D->getSpecialization()));
-
-  if (D->hasExplicitTemplateArgs()) {
-    TRY_TO(TraverseTemplateArgumentLocsHelper(
-        D->getTemplateArgsAsWritten()->getTemplateArgs(),
-        D->getTemplateArgsAsWritten()->NumTemplateArgs));
-  }
-})
-
 DEF_TRAVERSE_DECL(LinkageSpecDecl, {})
 
 DEF_TRAVERSE_DECL(ExportDecl, {})
@@ -2154,6 +2144,15 @@ bool RecursiveASTVisitor<Derived>::TraverseFunctionHelper(FunctionDecl *D) {
                                                   TALI->NumTemplateArgs));
       }
     }
+    // FIXME: Do we want to traverse the explicit template arguments for
+    // dependent friend function template specializations?
+  } else if (const DependentFunctionTemplateSpecializationInfo *DFSI =
+                 D->getDependentSpecializationInfo()) {
+    if (const ASTTemplateArgumentListInfo *TALI =
+            DFSI->TemplateArgumentsAsWritten) {
+      TRY_TO(TraverseTemplateArgumentLocsHelper(TALI->getTemplateArgs(),
+                                                TALI->NumTemplateArgs));
+    }
   }
 
   // Visit the function type itself, which can be either
diff --git a/clang/include/clang/Basic/DeclNodes.td b/clang/include/clang/Basic/DeclNodes.td
index 5e726c1bdf8fa5c..8b1f415dd5fe2cb 100644
--- a/clang/include/clang/Basic/DeclNodes.td
+++ b/clang/include/clang/Basic/DeclNodes.td
@@ -102,7 +102,6 @@ def FriendTemplate : DeclNode<Decl>;
 def StaticAssert : DeclNode<Decl>;
 def Block : DeclNode<Decl, "blocks">, DeclContext;
 def Captured : DeclNode<Decl>, DeclContext;
-def ClassScopeFunctionSpecialization : DeclNode<Decl>;
 def Import : DeclNode<Decl>;
 def OMPThreadPrivate : DeclNode<Decl>;
 def OMPAllocate : DeclNode<Decl>;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 0ac4df8edb242f6..a34ee0c1f8638ed 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5210,11 +5210,11 @@ def err_explicit_specialization_inconsistent_storage_class : Error<
   "'%select{none|extern|static|__private_extern__|auto|register}0'">;
 def err_dependent_function_template_spec_no_match : Error<
   "no candidate function template was found for dependent"
-  " friend function template specialization">;
+  " %select{member|friend}0 function template specialization">;
 def note_dependent_function_template_spec_discard_reason : Note<
-  "candidate ignored: %select{not a function template"
-  "|not a member of the enclosing namespace;"
-  " did you mean to explicitly qualify the specialization?}0">;
+  "candidate ignored: %select{not a function template|"
+  "not a member of the enclosing %select{class template|"
+  "namespace; did you mean to explicitly qualify the specialization?}1}0">;
 
 // C++ class template specializations and out-of-line definitions
 def err_template_spec_needs_header : Error<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 47379e00a7445e3..3dae60c83a06929 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -8427,9 +8427,9 @@ class Sema final {
                                          SourceLocation PrevPtOfInstantiation,
                                          bool &SuppressNew);
 
-  bool CheckDependentFunctionTemplateSpecialization(FunctionDecl *FD,
-                    const TemplateArgumentListInfo &ExplicitTemplateArgs,
-                                                    LookupResult &Previous);
+  bool CheckDependentFunctionTemplateSpecialization(
+      FunctionDecl *FD, const TemplateArgumentListInfo *ExplicitTemplateArgs,
+      LookupResult &Previous);
 
   bool CheckFunctionTemplateSpecialization(
       FunctionDecl *FD, TemplateArgumentListInfo *ExplicitTemplateArgs,
diff --git a/clang/include/clang/Sema/Template.h b/clang/include/clang/Sema/Template.h
index 1de2cc6917b424a..28d603bf115950a 100644
--- a/clang/include/clang/Sema/Template.h
+++ b/clang/include/clang/Sema/Template.h
@@ -630,8 +630,6 @@ enum class TemplateSubstitutionKind : char {
     // A few supplemental visitor functions.
     Decl *VisitCXXMethodDecl(CXXMethodDecl *D,
                              TemplateParameterList *TemplateParams,
-                             std::optional<const ASTTemplateArgumentListInfo *>
-                                 ClassScopeSpecializationArgs = std::nullopt,
                              RewriteKind RK = RewriteKind::None);
     Decl *VisitFunctionDecl(FunctionDecl *D,
                             TemplateParameterList *TemplateParams,
diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
index 9e115f2a5cce3f9..3141283667466c8 100644
--- a/clang/include/clang/Serialization/ASTBitCodes.h
+++ b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -1481,10 +1481,6 @@ enum DeclCode {
   /// template template parameter pack.
   DECL_EXPANDED_TEMPLATE_TEMPLATE_PARM_PACK,
 
-  /// A ClassScopeFunctionSpecializationDecl record a class scope
-  /// function specialization. (Microsoft extension).
-  DECL_CLASS_SCOPE_FUNCTION_SPECIALIZATION,
-
   /// An ImportDecl recording a module import.
   DECL_IMPORT,
 
diff --git a/clang/include/clang/Serialization/ASTRecordReader.h b/clang/include/clang/Serialization/ASTRecordReader.h
index ca85163e0f21c6d..d643e54e3d923a7 100644
--- a/clang/include/clang/Serialization/ASTRecordReader.h
+++ b/clang/include/clang/Serialization/ASTRecordReader.h
@@ -155,6 +155,8 @@ class ASTRecordReader
   /// Reads a TemplateArgumentLoc, advancing Idx.
   TemplateArgumentLoc readTemplateArgumentLoc();
 
+  void readTemplateArgumentListInfo(TemplateArgumentListInfo &Result);
+
   const ASTTemplateArgumentListInfo*
   readASTTemplateArgumentListInfo();
 
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index c7c2aecc8b179a4..1a6c49f0bdbd8e9 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -3342,27 +3342,25 @@ Error ASTNodeImporter::ImportTemplateInformation(
 
   case FunctionDecl::TK_DependentFunctionTemplateSpecialization: {
     auto *FromInfo = FromFD->getDependentSpecializationInfo();
-    UnresolvedSet<8> TemplDecls;
-    unsigned NumTemplates = FromInfo->getNumTemplates();
-    for (unsigned I = 0; I < NumTemplates; I++) {
-      if (Expected<FunctionTemplateDecl *> ToFTDOrErr =
-          import(FromInfo->getTemplate(I)))
-        TemplDecls.addDecl(*ToFTDOrErr);
+    UnresolvedSet<8> Candidates;
+    for (FunctionTemplateDecl *FTD : FromInfo->getCandidates()) {
+      if (Expected<FunctionTemplateDecl *> ToFTDOrErr = import(FTD))
+        Candidates.addDecl(*ToFTDOrErr);
       else
         return ToFTDOrErr.takeError();
     }
 
     // Import TemplateArgumentListInfo.
     TemplateArgumentListInfo ToTAInfo;
-    if (Error Err = ImportTemplateArgumentListInfo(
-            FromInfo->getLAngleLoc(), FromInfo->getRAngleLoc(),
-            llvm::ArrayRef(FromInfo->getTemplateArgs(),
-                           FromInfo->getNumTemplateArgs()),
-            ToTAInfo))
-      return Err;
+    const auto *FromTAArgsAsWritten = FromInfo->TemplateArgumentsAsWritten;
+    if (FromTAArgsAsWritten)
+      if (Error Err =
+              ImportTemplateArgumentListInfo(*FromTAArgsAsWritten, ToTAInfo))
+        return Err;
 
-    ToFD->setDependentTemplateSpecialization(Importer.getToContext(),
-                                             TemplDecls, ToTAInfo);
+    ToFD->setDependentTemplateSpecialization(
+        Importer.getToContext(), Candidates,
+        FromTAArgsAsWritten ? &ToTAInfo : nullptr);
     return Error::success();
   }
   }
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 08ae2087cfe70eb..a49751d04414a4c 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3961,6 +3961,12 @@ void FunctionDecl::setDescribedFunctionTemplate(
   TemplateOrSpecialization = Template;
 }
 
+bool FunctionDecl::isFunctionTemplateSpecialization() const {
+  return TemplateOrSpecialization.is<FunctionTemplateSpecializationInfo *>() ||
+         TemplateOrSpecialization
+             .is<DependentFunctionTemplateSpecializationInfo *>();
+}
+
 void FunctionDecl::setInstantiatedFromDecl(FunctionDecl *FD) {
   assert(TemplateOrSpecialization.isNull() &&
          "Function is already a specialization");
@@ -4095,6 +4101,11 @@ FunctionDecl::getTemplateSpecializationArgsAsWritten() const {
             .dyn_cast<FunctionTemplateSpecializationInfo*>()) {
     return Info->TemplateArgumentsAsWritten;
   }
+  if (DependentFunctionTemplateSpecializationInfo *Info =
+          TemplateOrSpecialization
+              .dyn_cast<DependentFunctionTemplateSpecializationInfo *>()) {
+    return Info->TemplateArgumentsAsWritten;
+  }
   return nullptr;
 }
 
@@ -4123,10 +4134,9 @@ FunctionDecl::setFunctionTemplateSpecialization(ASTContext &C,
   Template->addSpecialization(Info, InsertPos);
 }
 
-void
-FunctionDecl::setDependentTemplateSpecialization(ASTContext &Context,
-                                    const UnresolvedSetImpl &Templates,
-                             const TemplateArgumentListInfo &TemplateArgs) {
+void FunctionDecl::setDependentTemplateSpecialization(
+    ASTContext &Context, const UnresolvedSetImpl &Templates,
+    const TemplateArgumentListInfo *TemplateArgs) {
   assert(TemplateOrSpecialization.isNull());
   DependentFunctionTemplateSpecializationInfo *Info =
       DependentFunctionTemplateSpecializationInfo::Create(Context, Templates,
@@ -4142,28 +4152,26 @@ FunctionDecl::getDependentSpecializationInfo() const {
 
 DependentFunctionTemplateSpecializationInfo *
 DependentFunctionTemplateSpecializationInfo::Create(
-    ASTContext &Context, const UnresolvedSetImpl &Ts,
-    const TemplateArgumentListInfo &TArgs) {
-  void *Buffer = Context.Allocate(
-      totalSizeToAlloc<TemplateArgumentLoc, FunctionTemplateDecl *>(
-          TArgs.size(), Ts.size()));
-  return new (Buffer) DependentFunctionTemplateSpecializationInfo(Ts, TArgs);
+    ASTContext &Context, const UnresolvedSetImpl &Candidates,
+    const TemplateArgumentListInfo *TArgs) {
+  const auto *TArgsWritten =
+      TArgs ? ASTTemplateArgumentListInfo::Create(Context, *TArgs) : nullptr;
+  return new (Context.Allocate(
+      totalSizeToAlloc<FunctionTemplateDecl *>(Candidates.size())))
+      DependentFunctionTemplateSpecializationInfo(Candidates, TArgsWritten);
 }
 
 DependentFunctionTemplateSpecializationInfo::
-DependentFunctionTemplateSpecializationInfo(const UnresolvedSetImpl &Ts,
-                                      const TemplateArgumentListInfo &TArgs)
-  : AngleLocs(TArgs.getLAngleLoc(), TArgs.getRAngleLoc()) {
-  NumTemplates = Ts.size();
-  NumArgs = TArgs.size();
-
-  FunctionTemplateDecl **TsArray = getTrailingObjects<FunctionTemplateDecl *>();
-  for (unsigned I = 0, E = Ts.size(); I != E; ++I)
-    TsArray[I] = cast<FunctionTemplateDecl>(Ts[I]->getUnderlyingDecl());
-
-  TemplateArgumentLoc *ArgsArray = getTrailingObjects<TemplateArgumentLoc>();
-  for (unsigned I = 0, E = TArgs.size(); I != E; ++I)
-    new (&ArgsArray[I]) TemplateArgumentLoc(TArgs[I]);
+    DependentFunctionTemplateSpecializationInfo(
+        const UnresolvedSetImpl &Candidates,
+        const ASTTemplateArgumentListInfo *TemplateArgsWritten)
+    : TemplateArgumentsAsWritten(TemplateArgsWritten),
+      NumCandidates(Candidates.size()) {
+  std::transform(Candidates.begin(), Candidates.end(),
+                 getTrailingObjects<FunctionTemplateDecl *>(),
+                 [](NamedDecl *ND) {
+                   return cast<FunctionTemplateDecl>(ND->getUnderlyingDecl());
+                 });
 }
 
 TemplateSpecializationKind FunctionDecl::getTemplateSpecializationKind() const {
@@ -4178,6 +4186,13 @@ TemplateSpecializationKind FunctionDecl::getTemplateSpecializationKind() const {
           TemplateOrSpecialization.dyn_cast<MemberSpecializationInfo *>())
     return MSInfo->getTemplateSpecializationKind();
 
+  // A dependent function template specialization is an explicit specialization,
+  // except when it's a friend declaration.
+  if (TemplateOrSpecialization
+          .is<DependentFunctionTemplateSpecializationInfo *>() &&
+      getFriendObjectKind() == FOK_None)
+    return TSK_ExplicitSpecialization;
+
   return TSK_Undeclared;
 }
 
@@ -4192,6 +4207,11 @@ FunctionDecl::getTemplateSpecializationKindForInstantiation() const {
   //   template<> void f<int>() {}
   // };
   //
+  // Within the templated CXXRecordDecl, A<T>::f<int> is a dependent function
+  // template specialization; both getTemplateSpecializationKind() and
+  // getTemplateSpecializationKindForInstantiation() will return
+  // TSK_ExplicitSpecialization.
+  //
   // For A<int>::f<int>():
   // * getTemplateSpecializationKind() will return TSK_ExplicitSpecialization
   // * getTemplateSpecializationKindForInstantiation() will return
@@ -4212,6 +4232,11 @@ FunctionDecl::getTemplateSpecializationKindForInstantiation() const {
           TemplateOrSpecialization.dyn_cast<MemberSpecializationInfo *>())
     return MSInfo->getTemplateSpecializationKind();
 
+  if (TemplateOrSpecialization
+          .is<DependentFunctionTemplateSpecializationInfo *>() &&
+      getFriendObjectKind() == FOK_None)
+    return TSK_ExplicitSpecialization;
+
   return TSK_Undeclared;
 }
 
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 834beef49a44417..6048718854d6988 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -862,7 +862,6 @@ unsigned Decl::getIdentifierNamespaceForKind(Kind DeclKind) {
     case BuiltinTemplate:
     case ClassTemplateSpecialization:
     case ClassTemplatePartialSpecialization:
-    case ClassScopeFunctionSpecialization:
     case VarTemplateSpecialization:
     case VarTemplatePartialSpecialization:
     case ObjCImplementation:
@@ -1004,7 +1003,6 @@ bool Decl::AccessDeclContextCheck() const {
       // FIXME: a ClassTemplateSpecialization or CXXRecordDecl can have
       // AS_none as access specifier.
       isa<CXXRecordDecl>(this) ||
-      isa<ClassScopeFunctionSpecializationDecl>(this) ||
       isa<LifetimeExtendedTemporaryDecl>(this))
     return true;
 
diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
index 5e2742b4949f260..be385ca1152546e 100644
--- a/clang/lib/AST/DeclTemplate.cpp
+++ b/clang/lib/AST/DeclTemplate.cpp
@@ -1195,19 +1195,6 @@ TypeAliasTemplateDecl::newCommon(ASTContext &C) const {
   return CommonPtr;
 }
 
-//===----------------------------------------------------------------------===//
-// ClassScopeFunctionSpecializationDecl Implementation
-//===----------------------------------------------------------------------===//
-
-void ClassScopeFunctionSpecializationDecl::anchor() {}
-
-ClassScopeFunctionSpecializationDecl *
-ClassScopeFunctionSpecializationDecl::CreateDeserialized(ASTContext &C,
-                                                         unsigned ID) {
-  return new (C, ID) ClassScopeFunctionSpecializationDecl(
-      nullptr, SourceLocation(), nullptr, nullptr);
-}
-
 //===----------------------------------------------------------------------===//
 // VarTemplateDecl Implementation
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/AST/ODRHash.cpp b/clang/lib/AST/ODRHash.cpp
index 5eab315793b4113..7f9b5eb52e367eb 100644
--- a/clang/lib/AST/ODRHash.cpp
+++ b/clang/lib/AST/ODRHash.cpp
@@ -658,6 +658,10 @@ void ODRHash::AddFunctionDecl(const FunctionDecl *Function,
       if (F->isFunctionTemplateSpecialization()) {
         if (!isa<CXXMethodDecl>(DC)) return;
         if (DC->getLexicalParent()->isFileContext()) return;
+        // Skip class scope explicit function template specializations,
+        // as they have not yet been instantiated.
+        if (F->getDependentSpecializationInfo())
+          return;
         // Inline method specializations are the only supported
         // specialization for now.
       }
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 99b94588f56f0a5..4d4c94d008c9dfc 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -96,7 +96,6 @@ void CodeGenFunction::EmitDecl(const Decl &D) {
   case Decl::FriendTemplate:
   case Decl::Block:
   case Decl::Captured:
-  case Decl::ClassScopeFunctionSpecialization:
   case Decl::UsingShadow:
   case Decl::ConstructorUsingShadow:
   case Decl::ObjCTypeParam:
diff --git a/clang/lib/Index/IndexSymbol.cpp b/clang/lib/Index/IndexSymbol.cpp
index d7316538f606141..cfdffeed834e687 100644
--- a/clang/lib/Index/IndexSymbol.cpp
+++ b/clang/lib/Index/IndexSymbol.cpp
@@ -346,7 +346,6 @@ SymbolInfo index::getSymbolInfo(const Decl *D) {
       }
       break;
     case Decl::ClassTemplatePartialSpecialization:
-    case Decl::ClassScopeFunctionSpecialization:
     case Decl::ClassTemplateSpecialization:
     case Decl::CXXRecord:
     case Decl::Enum:
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 7d92e93188610c0..0e9717e6293b4ca 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -9774,7 +9774,6 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
   bool isMemberSpecialization = false;
   bool isFunctionTemplateSpecialization = false;
 
-  bool isDependentClassScopeExplicitSpecialization = false;
   bool HasExplicitTemplateArgs = false;
   TemplateArgumentListInfo TemplateArgs;
 
@@ -10414,12 +10413,12 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
           << SourceRange(TemplateId->LAngleLoc, TemplateId->RAngleLoc);
 
         HasExplicitTemplateArgs = false;
-      } else {
-        assert((isFunctionTemplateSpecialization ||
-                D.getDeclSpec().isFriendSpecified()) &&
-               "should have a 'template<>' for this decl");
+      } else if (isFriend) {
         // "friend void foo<>(int);" is an implicit specialization decl.
         isFunctionTemplateSpecialization = true;
+      } else {
+        assert(isFunctionTemplateSpecialization &&
+               "should have a 'template<>' for this decl");
       }
     } else if (isFriend && isFunctionTemplateSpecialization) {
       // This combination is only possible in a recovery case;  the user
@@ -10442,32 +10441,54 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     if (getLangOpts().CUDA && !isFunctionTemplateSpecialization)
       maybeAddCUDAHostDeviceAttrs(NewFD, Previous);
 
-    // If it's a friend (and only if it's a friend), it's possible
-    // that either the specialized function type or the specialized
-    // template is dependent, and therefore matching will fail.  In
-    // this case, don't check the specialization yet.
-    if (isFunctionTemplateSpecialization && isFriend &&
-        (NewFD->getType()->isDependentType() || DC->isDependentContext() ||
-         TemplateSpecializationType::anyInstantiationDependentTemplateArguments(
-             TemplateArgs.arguments()))) {
-      assert(HasExplicitTemplateArgs &&
-             "friend function specialization without template args");
-      if (CheckDependentFunctionTemplateSpecialization(NewFD, TemplateArgs,
-                                                       Previous))
-        NewFD->setInvalidDecl();
-    } else if (isFunctionTemplateSpecialization) {
-      if (CurContext->isDependentContext() && CurContext->isRecord()
-          && !isFriend) {
-        isDependentClassScopeExplicitSpecialization = true;
-      } else if (!NewFD->isInvalidDecl() &&
-                 CheckFunctionTemplateSpecialization(
-                     NewFD, (HasExplicitTemplateArgs ? &TemplateArgs : nullptr),
-                     Previous))
-        NewFD->setInvalidDecl();
+    // Handle explict specializations of function templates
+    // and friend function declarations with an explicit
+    // template argument list.
+    if (isFunctionTemplateSpecialization) {
+      bool isDependentSpecialization = false;
+      if (isFriend) {
+        // For friend function specializations, this is a dependent
+        // specialization if its semantic context is dependent, its
+        // type is dependent, or if its template-id is dependent.
+        isDependentSpecialization =
+            DC->isDependentContext() || NewFD->getType()->isDependentType() ||
+            (HasExplicitTemplateArgs &&
+             TemplateSpecializationType::
+                 anyInstantiationDependentTemplateArguments(
+                     TemplateArgs.arguments()));
+        assert(!isDependentSpecialization ||
+               (HasExplicitTemplateArgs == isDependentSpecialization) &&
+                   "dependent friend function specialization without template "
+                   "args");
+      } else {
+        // For class-scope explicit specializations of function templates,
+        // if the lexical context is dependent, then the specialization
+        // is dependent.
+        isDependentSpecialization =
+            CurContext->isRecord() && CurContext->isDependentContext();
+      }
+
+      TemplateArgumentListInfo *ExplicitTemplateArgs =
+          HasExplicitTemplateArgs ? &TemplateArgs : nullptr;
+      if (isDependentSpecialization) {
+        // If it's a dependent specialization, it may not be possible
+        // to determine the primary template (for explicit specializations)
+        // or befriended declaration (for friends) until the enclosing
+        // template is instantiated. In such cases, we store the declarations
+        // found by name lookup and defer resolution until instantiation.
+        if (CheckDependentFunctionTemplateSpecialization(
+                NewFD, ExplicitTemplateArgs, Previous))
+          NewFD->setInvalidDecl();
+      } else if (!NewFD->isInvalidDecl()) {
+        if (CheckFunctionTemplateSpecialization(NewFD, ExplicitTemplateArgs,
+                                                Previous))
+          NewFD->setInvalidDecl();
+      }
 
       // C++ [dcl.stc]p1:
       //   A storage-class-specifier shall not be specified in an explicit
       //   specialization (14.7.3)
+      // FIXME: We should be checking this for dependent specializations.
       FunctionTemplateSpecializationInfo *Info =
           NewFD->getTemplateSpecializationInfo();
       if (Info && SC != SC_None) {
@@ -10490,21 +10511,19 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     }
 
     // Perform semantic checking on the function declaration.
-    if (!isDependentClassScopeExplicitSpecialization) {
-      if (!NewFD->isInvalidDecl() && NewFD->isMain())
-        CheckMain(NewFD, D.getDeclSpec());
+    if (!NewFD->isInvalidDecl() && NewFD->isMain())
+      CheckMain(NewFD, D.getDeclSpec());
 
-      if (!NewFD->isInvalidDecl() && NewFD->isMSVCRTEntryPoint())
-        CheckMSVCRTEntryPoint(NewFD);
+    if (!NewFD->isInvalidDecl() && NewFD->isMSVCRTEntryPoint())
+      CheckMSVCRTEntryPoint(NewFD);
 
-      if (!NewFD->isInvalidDecl())
-        D.setRedeclaration(CheckFunctionDeclaration(S, NewFD, Previous,
-                                                    isMemberSpecialization,
-                                                    D.isFunctionDefinition()));
-      else if (!Previous.empty())
-        // Recover gracefully from an invalid redeclaration.
-        D.setRedeclaration(true);
-    }
+    if (!NewFD->isInvalidDecl())
+      D.setRedeclaration(CheckFunctionDeclaration(S, NewFD, Previous,
+                                                  isMemberSpecialization,
+                                                  D.isFunctionDefinition()));
+    else if (!Previous.empty())
+      // Recover gracefully from an invalid redeclaration.
+      D.setRedeclaration(true);
 
     assert((NewFD->isInvalidDecl() || NewFD->isMultiVersion() ||
             !D.isRedeclaration() ||
@@ -10816,19 +10835,6 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     }
   }
 
-  // Here we have an function template explicit specialization at class scope.
-  // The actual specialization will be postponed to template instatiation
-  // time via the ClassScopeFunctionSpecializationDecl node.
-  if (isDependentClassScopeExplicitSpecialization) {
-    ClassScopeFunctionSpecializationDecl *NewSpec =
-                         ClassScopeFunctionSpecializationDecl::Create(
-                                Context, CurContext, NewFD->getLocation(),
-                                cast<CXXMethodDecl>(NewFD),
-                                HasExplicitTemplateArgs, TemplateArgs);
-    CurContext->addDecl(NewSpec);
-    AddToScope = false;
-  }
-
   // Diagnose availability attributes. Availability cannot be used on functions
   // that are run during load/unload.
   if (const auto *attr = NewFD->getAttr<AvailabilityAttr>()) {
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 994d89e25b3848e..66688e0fed440c0 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -9327,10 +9327,9 @@ Sema::CheckSpecializationInstantiationRedecl(SourceLocation NewLoc,
 ///
 /// There really isn't any useful analysis we can do here, so we
 /// just store the information.
-bool
-Sema::CheckDependentFunctionTemplateSpecialization(FunctionDecl *FD,
-                   const TemplateArgumentListInfo &ExplicitTemplateArgs,
-                                                   LookupResult &Previous) {
+bool Sema::CheckDependentFunctionTemplateSpecialization(
+    FunctionDecl *FD, const TemplateArgumentListInfo *ExplicitTemplateArgs,
+    LookupResult &Previous) {
   // Remove anything from Previous that isn't a function template in
   // the correct context.
   DeclContext *FDLookupContext = FD->getDeclContext()->getRedeclContext();
@@ -9354,13 +9353,14 @@ Sema::CheckDependentFunctionTemplateSpecialization(FunctionDecl *FD,
   }
   F.done();
 
+  bool isFriend = FD->getFriendObjectKind() != Decl::FOK_None;
   if (Previous.empty()) {
-    Diag(FD->getLocation(),
-         diag::err_dependent_function_template_spec_no_match);
+    Diag(FD->getLocation(), diag::err_dependent_function_template_spec_no_match)
+        << isFriend;
     for (auto &P : DiscardedCandidates)
       Diag(P.second->getLocation(),
            diag::note_dependent_function_template_spec_discard_reason)
-          << P.first;
+          << P.first << isFriend;
     return true;
   }
 
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 37a7d6204413a38..085e885e294a626 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2239,42 +2239,46 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(
       D->isLocalExternDecl() ? Sema::ForExternalRedeclaration
                              : SemaRef.forRedeclarationInCurContext());
 
-  if (DependentFunctionTemplateSpecializationInfo *Info
-        = D->getDependentSpecializationInfo()) {
-    assert(isFriend && "non-friend has dependent specialization info?");
+  if (DependentFunctionTemplateSpecializationInfo *DFTSI =
+          D->getDependentSpecializationInfo()) {
+    assert(isFriend && "dependent specialization info on "
+                       "non-member non-friend function?");
 
     // Instantiate the explicit template arguments.
-    TemplateArgumentListInfo ExplicitArgs(Info->getLAngleLoc(),
-                                          Info->getRAngleLoc());
-    if (SemaRef.SubstTemplateArguments(Info->arguments(), TemplateArgs,
-                                       ExplicitArgs))
-      return nullptr;
-
-    // Map the candidate templates to their instantiations.
-    for (unsigned I = 0, E = Info->getNumTemplates(); I != E; ++I) {
-      Decl *Temp = SemaRef.FindInstantiatedDecl(D->getLocation(),
-                                                Info->getTemplate(I),
-                                                TemplateArgs);
-      if (!Temp) return nullptr;
+    TemplateArgumentListInfo ExplicitArgs;
+    if (const auto *ArgsWritten = DFTSI->TemplateArgumentsAsWritten) {
+      ExplicitArgs.setLAngleLoc(ArgsWritten->getLAngleLoc());
+      ExplicitArgs.setRAngleLoc(ArgsWritten->getRAngleLoc());
+      if (SemaRef.SubstTemplateArguments(ArgsWritten->arguments(), TemplateArgs,
+                                         ExplicitArgs))
+        return nullptr;
+    }
 
-      Previous.addDecl(cast<FunctionTemplateDecl>(Temp));
+    // Map the candidates for the primary template to their instantiations.
+    for (FunctionTemplateDecl *FTD : DFTSI->getCandidates()) {
+      if (NamedDecl *ND =
+              SemaRef.FindInstantiatedDecl(D->getLocation(), FTD, TemplateArgs))
+        Previous.addDecl(ND);
+      else
+        return nullptr;
     }
 
-    if (SemaRef.CheckFunctionTemplateSpecialization(Function,
-                                                    &ExplicitArgs,
-                                                    Previous))
+    if (SemaRef.CheckFunctionTemplateSpecialization(
+            Function,
+            DFTSI->TemplateArgumentsAsWritten ? &ExplicitArgs : nullptr,
+            Previous))
       Function->setInvalidDecl();
 
     IsExplicitSpecialization = true;
-  } else if (const ASTTemplateArgumentListInfo *Info =
+  } else if (const ASTTemplateArgumentListInfo *ArgsWritten =
                  D->getTemplateSpecializationArgsAsWritten()) {
     // The name of this function was written as a template-id.
     SemaRef.LookupQualifiedName(Previous, DC);
 
     // Instantiate the explicit template arguments.
-    TemplateArgumentListInfo ExplicitArgs(Info->getLAngleLoc(),
-                                          Info->getRAngleLoc());
-    if (SemaRef.SubstTemplateArguments(Info->arguments(), TemplateArgs,
+    TemplateArgumentListInfo ExplicitArgs(ArgsWritten->getLAngleLoc(),
+                                          ArgsWritten->getRAngleLoc());
+    if (SemaRef.SubstTemplateArguments(ArgsWritten->arguments(), TemplateArgs,
                                        ExplicitArgs))
       return nullptr;
 
@@ -2396,8 +2400,6 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(
 
 Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
     CXXMethodDecl *D, TemplateParameterList *TemplateParams,
-    std::optional<const ASTTemplateArgumentListInfo *>
-        ClassScopeSpecializationArgs,
     RewriteKind FunctionRewriteKind) {
   FunctionTemplateDecl *FunctionTemplate = D->getDescribedFunctionTemplate();
   if (FunctionTemplate && !TemplateParams) {
@@ -2627,41 +2629,41 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
 
   // If the name of this function was written as a template-id, instantiate
   // the explicit template arguments.
-  if (DependentFunctionTemplateSpecializationInfo *Info
-        = D->getDependentSpecializationInfo()) {
-    assert(isFriend && "non-friend has dependent specialization info?");
-
+  if (DependentFunctionTemplateSpecializationInfo *DFTSI =
+          D->getDependentSpecializationInfo()) {
     // Instantiate the explicit template arguments.
-    TemplateArgumentListInfo ExplicitArgs(Info->getLAngleLoc(),
-                                          Info->getRAngleLoc());
-    if (SemaRef.SubstTemplateArguments(Info->arguments(), TemplateArgs,
-                                       ExplicitArgs))
-      return nullptr;
-
-    // Map the candidate templates to their instantiations.
-    for (unsigned I = 0, E = Info->getNumTemplates(); I != E; ++I) {
-      Decl *Temp = SemaRef.FindInstantiatedDecl(D->getLocation(),
-                                                Info->getTemplate(I),
-                                                TemplateArgs);
-      if (!Temp) return nullptr;
+    TemplateArgumentListInfo ExplicitArgs;
+    if (const auto *ArgsWritten = DFTSI->TemplateArgumentsAsWritten) {
+      ExplicitArgs.setLAngleLoc(ArgsWritten->getLAngleLoc());
+      ExplicitArgs.setRAngleLoc(ArgsWritten->getRAngleLoc());
+      if (SemaRef.SubstTemplateArguments(ArgsWritten->arguments(), TemplateArgs,
+                                         ExplicitArgs))
+        return nullptr;
+    }
 
-      Previous.addDecl(cast<FunctionTemplateDecl>(Temp));
+    // Map the candidates for the primary template to their instantiations.
+    for (FunctionTemplateDecl *FTD : DFTSI->getCandidates()) {
+      if (NamedDecl *ND =
+              SemaRef.FindInstantiatedDecl(D->getLocation(), FTD, TemplateArgs))
+        Previous.addDecl(ND);
+      else
+        return nullptr;
     }
 
-    if (SemaRef.CheckFunctionTemplateSpecialization(Method,
-                                                    &ExplicitArgs,
-                                                    Previous))
+    if (SemaRef.CheckFunctionTemplateSpecialization(
+            Method, DFTSI->TemplateArgumentsAsWritten ? &ExplicitArgs : nullptr,
+            Previous))
       Method->setInvalidDecl();
 
     IsExplicitSpecialization = true;
-  } else if (const ASTTemplateArgumentListInfo *Info =
-                 ClassScopeSpecializationArgs.value_or(
-                     D->getTemplateSpecializationArgsAsWritten())) {
+  } else if (const ASTTemplateArgumentListInfo *ArgsWritten =
+                 D->getTemplateSpecializationArgsAsWritten()) {
     SemaRef.LookupQualifiedName(Previous, DC);
 
-    TemplateArgumentListInfo ExplicitArgs(Info->getLAngleLoc(),
-                                          Info->getRAngleLoc());
-    if (SemaRef.SubstTemplateArguments(Info->arguments(), TemplateArgs,
+    TemplateArgumentListInfo ExplicitArgs(ArgsWritten->getLAngleLoc(),
+                                          ArgsWritten->getRAngleLoc());
+
+    if (SemaRef.SubstTemplateArguments(ArgsWritten->arguments(), TemplateArgs,
                                        ExplicitArgs))
       return nullptr;
 
@@ -2670,14 +2672,6 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
                                                     Previous))
       Method->setInvalidDecl();
 
-    IsExplicitSpecialization = true;
-  } else if (ClassScopeSpecializationArgs) {
-    // Class-scope explicit specialization written without explicit template
-    // arguments.
-    SemaRef.LookupQualifiedName(Previous, DC);
-    if (SemaRef.CheckFunctionTemplateSpecialization(Method, nullptr, Previous))
-      Method->setInvalidDecl();
-
     IsExplicitSpecialization = true;
   } else if (!FunctionTemplate || TemplateParams || isFriend) {
     SemaRef.LookupQualifiedName(Previous, Record);
@@ -3502,13 +3496,6 @@ Decl *TemplateDeclInstantiator::VisitUsingPackDecl(UsingPackDecl *D) {
   return NewD;
 }
 
-Decl *TemplateDeclInstantiator::VisitClassScopeFunctionSpecializationDecl(
-    ClassScopeFunctionSpecializationDecl *Decl) {
-  CXXMethodDecl *OldFD = Decl->getSpecialization();
-  return cast_or_null<CXXMethodDecl>(
-      VisitCXXMethodDecl(OldFD, nullptr, Decl->getTemplateArgsAsWritten()));
-}
-
 Decl *TemplateDeclInstantiator::VisitOMPThreadPrivateDecl(
                                      OMPThreadPrivateDecl *D) {
   SmallVector<Expr *, 5> Vars;
@@ -4086,7 +4073,7 @@ FunctionDecl *Sema::SubstSpaceshipAsEqualEqual(CXXRecordDecl *RD,
   Decl *R;
   if (auto *MD = dyn_cast<CXXMethodDecl>(Spaceship)) {
     R = Instantiator.VisitCXXMethodDecl(
-        MD, nullptr, std::nullopt,
+        MD, nullptr,
         TemplateDeclInstantiator::RewriteKind::RewriteSpaceshipAsEqualEqual);
   } else {
     assert(Spaceship->getFriendObjectKind() &&
diff --git a/clang/lib/Serialization/ASTCommon.cpp b/clang/lib/Serialization/ASTCommon.cpp
index 72e582107480976..6110e287b7fb50f 100644
--- a/clang/lib/Serialization/ASTCommon.cpp
+++ b/clang/lib/Serialization/ASTCommon.cpp
@@ -424,7 +424,6 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::StaticAssert:
   case Decl::Block:
   case Decl::Captured:
-  case Decl::ClassScopeFunctionSpecialization:
   case Decl::Import:
   case Decl::OMPThreadPrivate:
   case Decl::OMPAllocate:
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 0952244d037a77c..4b4b3b8e2bcbeae 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -7383,15 +7383,20 @@ TemplateArgumentLoc ASTRecordReader::readTemplateArgumentLoc() {
   return TemplateArgumentLoc(Arg, readTemplateArgumentLocInfo(Arg.getKind()));
 }
 
-const ASTTemplateArgumentListInfo *
-ASTRecordReader::readASTTemplateArgumentListInfo() {
-  SourceLocation LAngleLoc = readSourceLocation();
-  SourceLocation RAngleLoc = readSourceLocation();
+void ASTRecordReader::readTemplateArgumentListInfo(
+    TemplateArgumentListInfo &Result) {
+  Result.setLAngleLoc(readSourceLocation());
+  Result.setRAngleLoc(readSourceLocation());
   unsigned NumArgsAsWritten = readInt();
-  TemplateArgumentListInfo TemplArgsInfo(LAngleLoc, RAngleLoc);
   for (unsigned i = 0; i != NumArgsAsWritten; ++i)
-    TemplArgsInfo.addArgument(readTemplateArgumentLoc());
-  return ASTTemplateArgumentListInfo::Create(getContext(), TemplArgsInfo);
+    Result.addArgument(readTemplateArgumentLoc());
+}
+
+const ASTTemplateArgumentListInfo *
+ASTRecordReader::readASTTemplateArgumentListInfo() {
+  TemplateArgumentListInfo Result;
+  readTemplateArgumentListInfo(Result);
+  return ASTTemplateArgumentListInfo::Create(getContext(), Result);
 }
 
 Decl *ASTReader::GetExternalDecl(uint32_t ID) {
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 88cb54a0365e62b..0a1ff254fd57d23 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -359,8 +359,6 @@ namespace clang {
 
     void VisitClassTemplatePartialSpecializationDecl(
                                      ClassTemplatePartialSpecializationDecl *D);
-    void VisitClassScopeFunctionSpecializationDecl(
-                                       ClassScopeFunctionSpecializationDecl *D);
     RedeclarableResult
     VisitVarTemplateSpecializationDeclImpl(VarTemplateSpecializationDecl *D);
 
@@ -950,27 +948,16 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
     Record.readTemplateArgumentList(TemplArgs, /*Canonicalize*/ true);
 
     // Template args as written.
-    SmallVector<TemplateArgumentLoc, 8> TemplArgLocs;
-    SourceLocation LAngleLoc, RAngleLoc;
-    bool HasTemplateArgumentsAsWritten = Record.readInt();
-    if (HasTemplateArgumentsAsWritten) {
-      unsigned NumTemplateArgLocs = Record.readInt();
-      TemplArgLocs.reserve(NumTemplateArgLocs);
-      for (unsigned i = 0; i != NumTemplateArgLocs; ++i)
-        TemplArgLocs.push_back(Record.readTemplateArgumentLoc());
-
-      LAngleLoc = readSourceLocation();
-      RAngleLoc = readSourceLocation();
-    }
+    TemplateArgumentListInfo TemplArgsWritten;
+    bool HasTemplateArgumentsAsWritten = Record.readBool();
+    if (HasTemplateArgumentsAsWritten)
+      Record.readTemplateArgumentListInfo(TemplArgsWritten);
 
     SourceLocation POI = readSourceLocation();
 
     ASTContext &C = Reader.getContext();
     TemplateArgumentList *TemplArgList
       = TemplateArgumentList::CreateCopy(C, TemplArgs);
-    TemplateArgumentListInfo TemplArgsInfo(LAngleLoc, RAngleLoc);
-    for (unsigned i = 0, e = TemplArgLocs.size(); i != e; ++i)
-      TemplArgsInfo.addArgument(TemplArgLocs[i]);
 
     MemberSpecializationInfo *MSInfo = nullptr;
     if (Record.readInt()) {
@@ -985,7 +972,7 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
     FunctionTemplateSpecializationInfo *FTInfo =
         FunctionTemplateSpecializationInfo::Create(
             C, FD, Template, TSK, TemplArgList,
-            HasTemplateArgumentsAsWritten ? &TemplArgsInfo : nullptr, POI,
+            HasTemplateArgumentsAsWritten ? &TemplArgsWritten : nullptr, POI,
             MSInfo);
     FD->TemplateOrSpecialization = FTInfo;
 
@@ -1016,21 +1003,20 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
   }
   case FunctionDecl::TK_DependentFunctionTemplateSpecialization: {
     // Templates.
-    UnresolvedSet<8> TemplDecls;
-    unsigned NumTemplates = Record.readInt();
-    while (NumTemplates--)
-      TemplDecls.addDecl(readDeclAs<NamedDecl>());
+    UnresolvedSet<8> Candidates;
+    unsigned NumCandidates = Record.readInt();
+    while (NumCandidates--)
+      Candidates.addDecl(readDeclAs<NamedDecl>());
 
     // Templates args.
-    TemplateArgumentListInfo TemplArgs;
-    unsigned NumArgs = Record.readInt();
-    while (NumArgs--)
-      TemplArgs.addArgument(Record.readTemplateArgumentLoc());
-    TemplArgs.setLAngleLoc(readSourceLocation());
-    TemplArgs.setRAngleLoc(readSourceLocation());
-
-    FD->setDependentTemplateSpecialization(Reader.getContext(),
-                                           TemplDecls, TemplArgs);
+    TemplateArgumentListInfo TemplArgsWritten;
+    bool HasTemplateArgumentsAsWritten = Record.readBool();
+    if (HasTemplateArgumentsAsWritten)
+      Record.readTemplateArgumentListInfo(TemplArgsWritten);
+
+    FD->setDependentTemplateSpecialization(
+        Reader.getContext(), Candidates,
+        HasTemplateArgumentsAsWritten ? &TemplArgsWritten : nullptr);
     // These are not merged; we don't need to merge redeclarations of dependent
     // template friends.
     break;
@@ -2521,14 +2507,6 @@ void ASTDeclReader::VisitClassTemplatePartialSpecializationDecl(
   }
 }
 
-void ASTDeclReader::VisitClassScopeFunctionSpecializationDecl(
-                                    ClassScopeFunctionSpecializationDecl *D) {
-  VisitDecl(D);
-  D->Specialization = readDeclAs<CXXMethodDecl>();
-  if (Record.readInt())
-    D->TemplateArgs = Record.readASTTemplateArgumentListInfo();
-}
-
 void ASTDeclReader::VisitFunctionTemplateDecl(FunctionTemplateDecl *D) {
   RedeclarableResult Redecl = VisitRedeclarableTemplateDecl(D);
 
@@ -3877,9 +3855,6 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   case DECL_VAR_TEMPLATE_PARTIAL_SPECIALIZATION:
     D = VarTemplatePartialSpecializationDecl::CreateDeserialized(Context, ID);
     break;
-  case DECL_CLASS_SCOPE_FUNCTION_SPECIALIZATION:
-    D = ClassScopeFunctionSpecializationDecl::CreateDeserialized(Context, ID);
-    break;
   case DECL_FUNCTION_TEMPLATE:
     D = FunctionTemplateDecl::CreateDeserialized(Context, ID);
     break;
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 65bee806d2c5571..2d3a126cabbafd1 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1029,7 +1029,6 @@ void ASTWriter::WriteBlockInfoBlock() {
   RECORD(DECL_INDIRECTFIELD);
   RECORD(DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK);
   RECORD(DECL_EXPANDED_TEMPLATE_TEMPLATE_PARM_PACK);
-  RECORD(DECL_CLASS_SCOPE_FUNCTION_SPECIALIZATION);
   RECORD(DECL_IMPORT);
   RECORD(DECL_OMP_THREADPRIVATE);
   RECORD(DECL_EMPTY);
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 4426f5c22277ed1..78ddf00cf3e1370 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -81,8 +81,6 @@ namespace clang {
     void VisitVarTemplateSpecializationDecl(VarTemplateSpecializationDecl *D);
     void VisitVarTemplatePartialSpecializationDecl(
         VarTemplatePartialSpecializationDecl *D);
-    void VisitClassScopeFunctionSpecializationDecl(
-                                       ClassScopeFunctionSpecializationDecl *D);
     void VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D);
     void VisitValueDecl(ValueDecl *D);
     void VisitEnumConstantDecl(EnumConstantDecl *D);
@@ -617,15 +615,9 @@ void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
 
     // Template args as written.
     Record.push_back(FTSInfo->TemplateArgumentsAsWritten != nullptr);
-    if (FTSInfo->TemplateArgumentsAsWritten) {
-      Record.push_back(FTSInfo->TemplateArgumentsAsWritten->NumTemplateArgs);
-      for (int i=0, e = FTSInfo->TemplateArgumentsAsWritten->NumTemplateArgs;
-             i!=e; ++i)
-        Record.AddTemplateArgumentLoc(
-            (*FTSInfo->TemplateArgumentsAsWritten)[i]);
-      Record.AddSourceLocation(FTSInfo->TemplateArgumentsAsWritten->LAngleLoc);
-      Record.AddSourceLocation(FTSInfo->TemplateArgumentsAsWritten->RAngleLoc);
-    }
+    if (FTSInfo->TemplateArgumentsAsWritten)
+      Record.AddASTTemplateArgumentListInfo(
+          FTSInfo->TemplateArgumentsAsWritten);
 
     Record.AddSourceLocation(FTSInfo->getPointOfInstantiation());
 
@@ -650,17 +642,16 @@ void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
     DependentFunctionTemplateSpecializationInfo *
       DFTSInfo = D->getDependentSpecializationInfo();
 
-    // Templates.
-    Record.push_back(DFTSInfo->getNumTemplates());
-    for (int i=0, e = DFTSInfo->getNumTemplates(); i != e; ++i)
-      Record.AddDeclRef(DFTSInfo->getTemplate(i));
+    // Candidates.
+    Record.push_back(DFTSInfo->getCandidates().size());
+    for (FunctionTemplateDecl *FTD : DFTSInfo->getCandidates())
+      Record.AddDeclRef(FTD);
 
     // Templates args.
-    Record.push_back(DFTSInfo->getNumTemplateArgs());
-    for (int i=0, e = DFTSInfo->getNumTemplateArgs(); i != e; ++i)
-      Record.AddTemplateArgumentLoc(DFTSInfo->getTemplateArg(i));
-    Record.AddSourceLocation(DFTSInfo->getLAngleLoc());
-    Record.AddSourceLocation(DFTSInfo->getRAngleLoc());
+    Record.push_back(DFTSInfo->TemplateArgumentsAsWritten != nullptr);
+    if (DFTSInfo->TemplateArgumentsAsWritten)
+      Record.AddASTTemplateArgumentListInfo(
+          DFTSInfo->TemplateArgumentsAsWritten);
     break;
   }
   }
@@ -1746,17 +1737,6 @@ void ASTDeclWriter::VisitVarTemplatePartialSpecializationDecl(
   Code = serialization::DECL_VAR_TEMPLATE_PARTIAL_SPECIALIZATION;
 }
 
-void ASTDeclWriter::VisitClassScopeFunctionSpecializationDecl(
-                                    ClassScopeFunctionSpecializationDecl *D) {
-  VisitDecl(D);
-  Record.AddDeclRef(D->getSpecialization());
-  Record.push_back(D->hasExplicitTemplateArgs());
-  if (D->hasExplicitTemplateArgs())
-    Record.AddASTTemplateArgumentListInfo(D->getTemplateArgsAsWritten());
-  Code = serialization::DECL_CLASS_SCOPE_FUNCTION_SPECIALIZATION;
-}
-
-
 void ASTDeclWriter::VisitFunctionTemplateDecl(FunctionTemplateDecl *D) {
   VisitRedeclarableTemplateDecl(D);
 
diff --git a/clang/lib/StaticAnalyzer/Checkers/SmartPtrModeling.cpp b/clang/lib/StaticAnalyzer/Checkers/SmartPtrModeling.cpp
index a20d24db158f50b..66e9a501c348eb5 100644
--- a/clang/lib/StaticAnalyzer/Checkers/SmartPtrModeling.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/SmartPtrModeling.cpp
@@ -202,7 +202,7 @@ static QualType getInnerPointerType(CheckerContext C, const CXXRecordDecl *RD) {
 static QualType getPointerTypeFromTemplateArg(const CallEvent &Call,
                                               CheckerContext &C) {
   const auto *FD = dyn_cast_or_null<FunctionDecl>(Call.getDecl());
-  if (!FD || !FD->isFunctionTemplateSpecialization())
+  if (!FD || !FD->getPrimaryTemplate())
     return {};
   const auto &TemplateArgs = FD->getTemplateSpecializationArgs()->asArray();
   if (TemplateArgs.size() == 0)
diff --git a/clang/test/AST/ast-dump-decl.cpp b/clang/test/AST/ast-dump-decl.cpp
index 6848a2b01da2c91..017e640aeaea6d7 100644
--- a/clang/test/AST/ast-dump-decl.cpp
+++ b/clang/test/AST/ast-dump-decl.cpp
@@ -645,11 +645,16 @@ class TestClassScopeFunctionSpecialization {
   template<class U> void foo(U a) { }
   template<> void foo<int>(int a) { }
 };
-// CHECK:      ClassScopeFunctionSpecializationDecl
-// CHECK-NEXT:   CXXMethod{{.*}} foo 'void (int)'
+// CHECK:      FunctionTemplateDecl{{.*}} foo
+// CHECK-NEXT:   TemplateTypeParmDecl{{.*}} referenced class depth 1 index 0 U
+// CHECK-NEXT:   CXXMethodDecl{{.*}} foo 'void (U)' implicit-inline
 // CHECK-NEXT:     ParmVarDecl
 // CHECK-NEXT:     CompoundStmt
+// CHECK-NEXT: CXXMethodDecl{{.*}} foo 'void (int)' explicit_specialization implicit-inline
 // CHECK-NEXT:   TemplateArgument{{.*}} 'int'
+// CHECK-NEXT:     BuiltinType{{.*}} 'int'
+// CHECK-NEXT:   ParmVarDecl
+// CHECK-NEXT:   CompoundStmt
 
 namespace TestTemplateTypeParmDecl {
   template<typename ... T, class U = int> void foo();
diff --git a/clang/test/CXX/drs/dr7xx.cpp b/clang/test/CXX/drs/dr7xx.cpp
index f6a2e5923bedb5d..11901b80d646225 100644
--- a/clang/test/CXX/drs/dr7xx.cpp
+++ b/clang/test/CXX/drs/dr7xx.cpp
@@ -111,6 +111,11 @@ namespace dr727 { // dr727: partial
 
     template<typename T> struct C<T*> {};
     template<typename T> static const int N<T*>;
+
+    template<typename>
+    struct E {
+      template<> void f<void>() {} // expected-error {{no candidate function template}}
+    };
   };
 
   void d(D<int> di) {
diff --git a/clang/test/SemaTemplate/instantiate-method.cpp b/clang/test/SemaTemplate/instantiate-method.cpp
index 9cd668dacf5c9c5..666c8aea87aabd7 100644
--- a/clang/test/SemaTemplate/instantiate-method.cpp
+++ b/clang/test/SemaTemplate/instantiate-method.cpp
@@ -185,14 +185,11 @@ namespace SameSignatureAfterInstantiation {
 
 namespace PR22040 {
   template <typename T> struct Foobar {
-    template <> void bazqux(typename T::type) {}  // expected-error 2{{cannot be used prior to '::' because it has no members}}
+    template <> void bazqux(T) {}  // expected-error {{no candidate function template was found for dependent member function template specialization}}
   };
 
   void test() {
-    // FIXME: we should suppress the "no member" errors
-    Foobar<void>::bazqux();  // expected-error{{no member named 'bazqux' in }}  expected-note{{in instantiation of template class }}
-    Foobar<int>::bazqux();  // expected-error{{no member named 'bazqux' in }}  expected-note{{in instantiation of template class }}
-    Foobar<int>::bazqux(3);  // expected-error{{no member named 'bazqux' in }}
+    Foobar<int>::bazqux(1);
   }
 }
 
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
index f0c8ecfcb6264fb..4766561f5d4bd24 100644
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -6847,7 +6847,6 @@ CXCursor clang_getCursorDefinition(CXCursor C) {
   case Decl::Captured:
   case Decl::OMPCapturedExpr:
   case Decl::Label: // FIXME: Is this right??
-  case Decl::ClassScopeFunctionSpecialization:
   case Decl::CXXDeductionGuide:
   case Decl::Import:
   case Decl::OMPThreadPrivate:

>From d9f14d1fbc987c90406c4dd7be221cde3a43966d Mon Sep 17 00:00:00 2001
From: Krystian Stasiowski <sdkrystian at gmail.com>
Date: Tue, 19 Sep 2023 05:19:52 -0400
Subject: [PATCH 2/2] [FOLD]

---
 .../clang-tidy/modernize/UseEmplaceCheck.cpp  |  8 +++----
 clang/include/clang/AST/ASTNodeTraverser.h    |  6 +++--
 .../test/SemaTemplate/instantiate-method.cpp  | 22 ++++++++++---------
 3 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
index 06ae1f4e257528f..b85dde5644d313f 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEmplaceCheck.cpp
@@ -67,11 +67,9 @@ AST_MATCHER_P(CallExpr, hasLastArgument,
 // function had parameters defined (this is useful to check if there is only one
 // variadic argument).
 AST_MATCHER(CXXMemberCallExpr, hasSameNumArgsAsDeclNumParams) {
-  if (Node.getMethodDecl()->getPrimaryTemplate())
-    return Node.getNumArgs() == Node.getMethodDecl()
-                                    ->getPrimaryTemplate()
-                                    ->getTemplatedDecl()
-                                    ->getNumParams();
+  if (const FunctionTemplateDecl *Primary =
+          Node.getMethodDecl()->getPrimaryTemplate())
+    return Node.getNumArgs() == Primary->getTemplatedDecl()->getNumParams();
 
   return Node.getNumArgs() == Node.getMethodDecl()->getNumParams();
 }
diff --git a/clang/include/clang/AST/ASTNodeTraverser.h b/clang/include/clang/AST/ASTNodeTraverser.h
index c3d233d3ab4a259..cc8dab97f8b010f 100644
--- a/clang/include/clang/AST/ASTNodeTraverser.h
+++ b/clang/include/clang/AST/ASTNodeTraverser.h
@@ -426,9 +426,11 @@ class ASTNodeTraverser
   }
 
   void VisitFunctionDecl(const FunctionDecl *D) {
-    if (const auto *FTSI = D->getTemplateSpecializationInfo())
+    if (FunctionTemplateSpecializationInfo *FTSI =
+            D->getTemplateSpecializationInfo())
       dumpTemplateArgumentList(*FTSI->TemplateArguments);
-    else if (const auto *DFTSI = D->getDependentSpecializationInfo())
+    else if (DependentFunctionTemplateSpecializationInfo *DFTSI =
+                 D->getDependentSpecializationInfo())
       dumpASTTemplateArgumentListInfo(DFTSI->TemplateArgumentsAsWritten);
 
     if (D->param_begin())
diff --git a/clang/test/SemaTemplate/instantiate-method.cpp b/clang/test/SemaTemplate/instantiate-method.cpp
index 666c8aea87aabd7..60889a4cffe46ae 100644
--- a/clang/test/SemaTemplate/instantiate-method.cpp
+++ b/clang/test/SemaTemplate/instantiate-method.cpp
@@ -45,7 +45,7 @@ class HasDestructor {
   virtual ~HasDestructor() = 0;
 };
 
-int i = sizeof(HasDestructor<int>); // FIXME: forces instantiation, but 
+int i = sizeof(HasDestructor<int>); // FIXME: forces instantiation, but
                 // the code below should probably instantiate by itself.
 int abstract_destructor[__is_abstract(HasDestructor<int>)? 1 : -1];
 
@@ -94,7 +94,7 @@ struct X0 : X0Base {
 
 template<typename U>
 struct X1 : X0<U> {
-  int &f2() { 
+  int &f2() {
     return X0Base::f();
   }
 };
@@ -129,19 +129,19 @@ namespace test1 {
 }
 
 namespace PR6947 {
-  template< class T > 
+  template< class T >
   struct X {
-    int f0( )      
+    int f0( )
     {
       typedef void ( X::*impl_fun_ptr )( );
       impl_fun_ptr pImpl = &X::template
         f0_impl1<int>;
     }
-  private:                  
+  private:
     int f1() {
     }
-    template< class Processor>                  
-    void f0_impl1( )                 
+    template< class Processor>
+    void f0_impl1( )
     {
     }
   };
@@ -154,7 +154,7 @@ namespace PR6947 {
 }
 
 namespace PR7022 {
-  template <typename > 
+  template <typename >
   struct X1
   {
     typedef int state_t( );
@@ -185,11 +185,13 @@ namespace SameSignatureAfterInstantiation {
 
 namespace PR22040 {
   template <typename T> struct Foobar {
-    template <> void bazqux(T) {}  // expected-error {{no candidate function template was found for dependent member function template specialization}}
+    template <> void bazqux(typename T::type) {}  // expected-error {{no candidate function template was found for dependent member function template specialization}}
   };
 
   void test() {
-    Foobar<int>::bazqux(1);
+    Foobar<void>::bazqux();
+    Foobar<int>::bazqux();
+    Foobar<int>::bazqux(3);  // expected-error{{no member named 'bazqux' in }}
   }
 }
 



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