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
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 7acc22a..d01e2a1 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -518,6 +518,24 @@
     = 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 @@
     + 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);
 }