Fix a double free when parsing malformed code. Fixes rdar://9173693.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@130775 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Parse/ParseExprCXX.cpp

@@ -281,6 +281,9 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
         SS.SetInvalid(SourceRange(StartLoc, CCLoc));
       }
 
+      // If we are caching tokens we will process the TemplateId again,
+      // otherwise destroy it.
+      if (!PP.isBacktrackEnabled())
         TemplateId->Destroy();
       continue;
     }

test/SemaTemplate/rdar9173693.cpp

@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+// <rdar://problem/9173693>
+template< bool C > struct assert { };
+template< bool > struct assert_arg_pred_impl { }; // expected-note 3 {{declared here}}
+template< typename Pred > assert<false> assert_not_arg( void (*)(Pred), typename assert_arg_pred<Pred>::type ); // expected-error 5 {{}}