Only do delayed diagnostics if there were no errors when parsing the decl.

Fixes crash in http://llvm.org/PR10109 & rdar://9584039.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133816 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaDeclAttr.cpp

@@ -3258,7 +3258,7 @@ void Sema::DelayedDiagnostics::popParsingDecl(Sema &S, ParsingDeclState state,
 
   // We only want to actually emit delayed diagnostics when we
   // successfully parsed a decl.
-  if (decl) {
+  if (decl && !decl->isInvalidDecl()) {
     // We emit all the active diagnostics, not just those starting
     // from the saved state.  The idea is this:  we get one push for a
     // decl spec and another for each declarator;  in a decl group like:

test/SemaCXX/nested-name-spec.cpp

@@ -266,3 +266,22 @@ namespace rdar7980179 {
 
 namespace alias = A;
 double *dp = (alias::C*)0; // expected-error{{cannot initialize a variable of type 'double *' with an rvalue of type 'alias::C *'}}
+
+// http://llvm.org/PR10109
+namespace PR10109 {
+template<typename T>
+struct A {
+protected:
+  struct B;
+  struct B::C; // expected-error {{requires a template parameter list}} \
+               // expected-error {{no struct named 'C'}}
+};
+
+template<typename T>
+struct A2 {
+protected:
+  struct B;
+};
+template <typename T>
+struct A2<T>::B::C; // expected-error {{no struct named 'C'}}
+}