Test case for my r218780 patch.

Suggested by Richard Smith.
rdar://18508589.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@218830 91177308-0d34-0410-b5e6-96231b3b80d8

test/Parser/cxx-default-args.cpp

@@ -31,3 +31,8 @@ struct T {
   void f7(bool a = T1<int, bool>::V < 3);
   void f8(int = func<0,1<2>(0), int = 1<0, T1<int,int>(int) = 0);
 };
+
+// rdar://18508589
+struct S { 
+  void f(int &r = error);  // expected-error {{use of undeclared identifier 'error'}}
+};