In Microsoft mode, allow template function explicit specialization at class scope.

Necessary to parse MFC and MSVC standard lib code.

Example:
struct X {
  template<class T> void f(T) { }
  template<> void f(int) { } 
}

llvm-svn: 131347

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -1775,6 +1775,9 @@ def err_template_spec_decl_function_scope : Error<
   "explicit specialization of %0 in function scope">;
 def err_template_spec_decl_class_scope : Error<
   "explicit specialization of %0 in class scope">;
+def war_template_spec_decl_class_scope : ExtWarn<
+  "Allowing explicit specialization of %0 in class scope is a Microsoft "
+  "extension">, InGroup<Microsoft>;
 def err_template_spec_decl_friend : Error<
   "cannot declare an explicit specialization in a friend">;
 def err_template_spec_decl_out_of_scope_global : Error<

clang/lib/Sema/SemaDecl.cpp

@@ -1685,10 +1685,14 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, Decl *OldD) {
     if (OldMethod && NewMethod) {
       // Preserve triviality.
       NewMethod->setTrivial(OldMethod->isTrivial());
-
+   
+      // MSVC allows explicit template specialization at class scope.
+      bool IsMSExplicitSpecialization = getLangOptions().Microsoft &&
+                                 NewMethod->isFunctionTemplateSpecialization();
       bool isFriend = NewMethod->getFriendObjectKind();
 
-      if (!isFriend && NewMethod->getLexicalDeclContext()->isRecord()) {
+      if (!isFriend && NewMethod->getLexicalDeclContext()->isRecord() &&
+          !IsMSExplicitSpecialization) {
         //    -- Member function declarations with the same name and the
         //       same parameter types cannot be overloaded if any of them
         //       is a static member function declaration.

clang/lib/Sema/SemaTemplate.cpp

@@ -4401,9 +4401,12 @@ static bool CheckTemplateSpecializationScope(Sema &S,
   }
 
   if (S.CurContext->isRecord() && !IsPartialSpecialization) {
-    S.Diag(Loc, diag::err_template_spec_decl_class_scope)
-      << Specialized;
-    return true;
+    if (S.getLangOptions().Microsoft)
+      S.Diag(Loc, diag::war_template_spec_decl_class_scope) << Specialized;
+    else {    
+      S.Diag(Loc, diag::err_template_spec_decl_class_scope) << Specialized;
+      return true;
+    }
   }
 
   // C++ [temp.class.spec]p6:

clang/test/SemaCXX/MicrosoftExtensions.cpp

@@ -197,3 +197,10 @@ void pointer_to_integral_type_conv(char* ptr) {
    ch = (char)ptr;
    sh = (short)ptr;
 } 
+
+
+struct X1 {
+  template<typename T> void f(T);
+
+  template<> void f(int) { } // expected-warning{{Allowing explicit specialization of 'f' in class scope is a Microsoft extension}}
+};