Microsoft friend acting as a forward declaration; try#2. Now only 2 lines.

llvm-svn: 132387

clang/lib/Sema/SemaDecl.cpp

@@ -7016,8 +7016,8 @@ Decl *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
           // for the consumer of this Decl to know it doesn't own it.
           // For our current ASTs this shouldn't be a problem, but will
           // need to be changed with DeclGroups.
-          if ((TUK == TUK_Reference && !PrevTagDecl->getFriendObjectKind()) ||
-              TUK == TUK_Friend)
+          if ((TUK == TUK_Reference && (!PrevTagDecl->getFriendObjectKind() ||
+               getLangOptions().Microsoft)) || TUK == TUK_Friend)
             return PrevTagDecl;
 
           // Diagnose attempts to redefine a tag.
@@ -7259,8 +7259,12 @@ CreateNewDecl:
   New->setLexicalDeclContext(CurContext);
 
   // Mark this as a friend decl if applicable.
+  // In Microsoft mode, a friend declaration also acts as a forward
+  // declaration so we always pass true to setObjectOfFriendDecl to make
+  // the tag name visible.
   if (TUK == TUK_Friend)
-    New->setObjectOfFriendDecl(/* PreviouslyDeclared = */ !Previous.empty());
+    New->setObjectOfFriendDecl(/* PreviouslyDeclared = */ !Previous.empty() ||
+                               getLangOptions().Microsoft);
 
   // Set the access specifier.
   if (!Invalid && SearchDC->isRecord())

clang/test/SemaCXX/MicrosoftExtensions.cpp

@@ -226,4 +226,29 @@ private:
   using B::f; // expected-warning {{using declaration refers to inaccessible member 'ms_using_declaration_bug::B::f', which refers to accessible member 'ms_using_declaration_bug::A::f', accepted for Microsoft compatibility}}
 };
 
-}
+}
+
+
+
+namespace friend_as_a_forward_decl {
+
+class A {
+  class Nested {
+    friend class B;
+    B* b;
+  };
+  B* b;
+};
+B* global_b;
+
+
+void f()
+{
+  class Local {
+    friend class Z;
+    Z* b;
+  };
+  Z* b;
+}
+
+ }