Implement function template specialization at class scope extension in Microsoft mode. A new AST node is introduced: ClassScopeFunctionSpecialization. This node holds a FunctionDecl that is not yet specialized; then during the class template instantiation the ClassScopeFunctionSpecialization will spawn the actual function specialization.

Example:
template <class T>
class A {
public:
  template <class U> void f(U p) {  }
  template <> void f(int p) {  } // <== class scope specialization
};

This extension is necessary to parse MSVC standard C++ headers, MFC and ATL code.
BTW, with this feature in, clang can parse (-fsyntax-only) all the MSVC 2010 standard header files without any error.

llvm-svn: 137573

Author: fpichet

clang/include/clang/AST/ASTContext.h

@@ -152,6 +152,11 @@ class ASTContext : public llvm::RefCountedBase<ASTContext> {
   /// \brief Mapping from __block VarDecls to their copy initialization expr.
   llvm::DenseMap<const VarDecl*, Expr*> BlockVarCopyInits;
 
+  /// \brief Mapping from class scope functions specialization to their
+  ///  templateS pattern.
+  llvm::DenseMap<const FunctionDecl*, FunctionDecl*>
+    ClassScopeSpecilizationPattern;
+
   /// \brief Representation of a "canonical" template template parameter that
   /// is used in canonical template names.
   class CanonicalTemplateTemplateParm : public llvm::FoldingSetNode {
@@ -382,6 +387,11 @@ class ASTContext : public llvm::RefCountedBase<ASTContext> {
   MemberSpecializationInfo *getInstantiatedFromStaticDataMember(
                                                            const VarDecl *Var);
 
+  FunctionDecl *getClassScopeSpecializationPattern(const FunctionDecl *FD);
+
+  void setClassScopeSpecializationPattern(FunctionDecl *FD,
+                                          FunctionDecl *Pattern);
+
   /// \brief Note that the static data member \p Inst is an instantiation of
   /// the static data member template \p Tmpl of a class template.
   void setInstantiatedFromStaticDataMember(VarDecl *Inst, VarDecl *Tmpl,

clang/include/clang/AST/Decl.h

@@ -1851,7 +1851,11 @@ class FunctionDecl : public DeclaratorDecl, public DeclContext,
   bool isFunctionTemplateSpecialization() const {
     return getPrimaryTemplate() != 0;
   }
-       
+
+  /// \brief Retrieve the class scope template pattern that this function
+  ///  template specialization is instantiated from.
+  FunctionDecl *getClassScopeSpecializationPattern() const;
+
   /// \brief If this function is actually a function template specialization,
   /// retrieve information about this function template specialization. 
   /// Otherwise, returns NULL.

clang/include/clang/AST/DeclTemplate.h

@@ -2097,6 +2097,58 @@ class TypeAliasTemplateDecl : public RedeclarableTemplateDecl,
   friend class ASTDeclWriter;
 };
 
+/// Declaration of a function specialization at template class scope.
+/// This is a non standard extension needed to support MSVC.
+/// For example:
+/// template <class T>
+/// class A {
+///    template <class U> void foo(U a) { }
+///    template<> void foo(int a) { }
+/// }
+///
+/// "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.
+class ClassScopeFunctionSpecializationDecl : public Decl {
+private:
+  ClassScopeFunctionSpecializationDecl(DeclContext *DC, SourceLocation Loc,
+                                       CXXMethodDecl *FD)
+    : Decl(Decl::ClassScopeFunctionSpecialization, DC, Loc),
+      Specialization(FD) {}
+
+  ClassScopeFunctionSpecializationDecl(EmptyShell Empty)
+    : Decl(Decl::ClassScopeFunctionSpecialization, Empty) {}
+
+  CXXMethodDecl *Specialization;
+
+public:
+  CXXMethodDecl *getSpecialization() const { return Specialization; }
+
+  static ClassScopeFunctionSpecializationDecl *Create(ASTContext &C,
+                                                      DeclContext *DC,
+                                                      SourceLocation Loc,
+                                                      CXXMethodDecl *FD) {
+    return new (C) ClassScopeFunctionSpecializationDecl(DC , Loc, FD);
+  }
+
+  static ClassScopeFunctionSpecializationDecl *Create(ASTContext &Context,
+                                                      EmptyShell Empty) {
+    return new (Context)ClassScopeFunctionSpecializationDecl(0,
+                                                         SourceLocation(), 0);
+  }
+  // Implement isa/cast/dyncast/etc.
+  static bool classof(const Decl *D) { return classofKind(D->getKind()); }
+  static bool classofKind(Kind K) {
+    return K == Decl::ClassScopeFunctionSpecialization;
+  }
+  static bool classof(const ClassScopeFunctionSpecializationDecl *D) {
+    return true;
+  }
+
+  friend class ASTDeclReader;
+  friend class ASTDeclWriter;
+};
+
 /// Implementation of inline functions that require the template declarations
 inline AnyFunctionDecl::AnyFunctionDecl(FunctionTemplateDecl *FTD)
   : Function(FTD) { }

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -1114,6 +1114,10 @@ DEF_TRAVERSE_DECL(FriendTemplateDecl, {
     }
   })
 
+DEF_TRAVERSE_DECL(ClassScopeFunctionSpecializationDecl, {
+  TRY_TO(TraverseDecl(D->getSpecialization()));
+ })
+
 DEF_TRAVERSE_DECL(LinkageSpecDecl, { })
 
 DEF_TRAVERSE_DECL(ObjCClassDecl, {

clang/include/clang/Basic/DeclNodes.td

@@ -74,3 +74,4 @@ def Friend : Decl;
 def FriendTemplate : Decl;
 def StaticAssert : Decl;
 def Block : Decl, DeclContext;
+def ClassScopeFunctionSpecialization : Decl;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2028,6 +2028,9 @@ def err_not_class_template_specialization : Error<
   "parameter}0">;
 def err_function_specialization_in_class : Error<
   "cannot specialize a function %0 within class scope">;
+def ext_function_specialization_in_class : ExtWarn<
+  "explicit specialization of %0 within class scope in a Microsoft extension">,
+  InGroup<Microsoft>;
 def ext_explicit_specialization_storage_class : ExtWarn<
   "explicit specialization cannot have a storage class">;
 def err_explicit_specialization_inconsistent_storage_class : Error<

clang/include/clang/Sema/Sema.h

@@ -1002,7 +1002,8 @@ class Sema {
                                      LookupResult &Previous,
                                      MultiTemplateParamsArg TemplateParamLists,
                                      bool IsFunctionDefinition,
-                                     bool &Redeclaration);
+                                     bool &Redeclaration,
+                                     bool &AddToScope);
   bool AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD);
   void DiagnoseHiddenVirtualMethods(CXXRecordDecl *DC, CXXMethodDecl *MD);
   void CheckFunctionDeclaration(Scope *S,

clang/include/clang/Sema/Template.h

@@ -350,7 +350,8 @@ namespace clang {
                             TemplateParameterList *TemplateParams = 0);
     Decl *VisitCXXRecordDecl(CXXRecordDecl *D);
     Decl *VisitCXXMethodDecl(CXXMethodDecl *D,
-                             TemplateParameterList *TemplateParams = 0);
+                             TemplateParameterList *TemplateParams = 0,
+                             bool IsClassScopeSpecialization = false);
     Decl *VisitCXXConstructorDecl(CXXConstructorDecl *D);
     Decl *VisitCXXDestructorDecl(CXXDestructorDecl *D);
     Decl *VisitCXXConversionDecl(CXXConversionDecl *D);
@@ -367,6 +368,8 @@ namespace clang {
     Decl *VisitUsingShadowDecl(UsingShadowDecl *D);
     Decl *VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
     Decl *VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D);
+    Decl *VisitClassScopeFunctionSpecializationDecl(
+                                      ClassScopeFunctionSpecializationDecl *D);
 
     // Base case. FIXME: Remove once we can instantiate everything.
     Decl *VisitDecl(Decl *D) {

clang/include/clang/Serialization/ASTBitCodes.h

@@ -826,7 +826,10 @@ namespace clang {
       DECL_INDIRECTFIELD,
       /// \brief A NonTypeTemplateParmDecl record that stores an expanded
       /// non-type template parameter pack.
-      DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK
+      DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK,
+      /// \brief A ClassScopeFunctionSpecializationDecl record a class scope
+      /// function specialization. (Microsoft extension).
+      DECL_CLASS_SCOPE_FUNCTION_SPECIALIZATION
     };
 
     /// \brief Record codes for each kind of statement or expression.

clang/lib/AST/ASTContext.cpp

@@ -518,6 +518,24 @@ ASTContext::setInstantiatedFromStaticDataMember(VarDecl *Inst, VarDecl *Tmpl,
     = new (*this) MemberSpecializationInfo(Tmpl, TSK, PointOfInstantiation);
 }
 
+FunctionDecl *ASTContext::getClassScopeSpecializationPattern(
+                                                     const FunctionDecl *FD){
+  assert(FD && "Specialization is 0");
+  llvm::DenseMap<const FunctionDecl*, FunctionDecl *>::const_iterator Pos
+    = ClassScopeSpecilizationPattern.find(FD);
+  if (Pos == ClassScopeSpecilizationPattern.end())
+    return 0;
+
+  return Pos->second;
+}
+
+void ASTContext::setClassScopeSpecializationPattern(FunctionDecl *FD,
+                                        FunctionDecl *Pattern) {
+  assert(FD && "Specialization is 0");
+  assert(Pattern && "Class scope specialization pattern is 0");
+  ClassScopeSpecilizationPattern[FD] = Pattern;
+}
+
 NamedDecl *
 ASTContext::getInstantiatedFromUsingDecl(UsingDecl *UUD) {
   llvm::DenseMap<UsingDecl *, NamedDecl *>::const_iterator Pos
@@ -6439,5 +6457,6 @@ size_t ASTContext::getSideTableAllocatedMemory() const {
     + llvm::capacity_in_bytes(InstantiatedFromUnnamedFieldDecl)
     + llvm::capacity_in_bytes(OverriddenMethods)
     + llvm::capacity_in_bytes(Types)
-    + llvm::capacity_in_bytes(VariableArrayTypes);
+    + llvm::capacity_in_bytes(VariableArrayTypes)
+    + llvm::capacity_in_bytes(ClassScopeSpecilizationPattern);
 }