Fix a couple of bugs, add some new cool stuff.

1. Fix a todo in Parser::ParseTag, to recover better.  On code like
   that in test/Sema/decl-invalid.c it causes us to return a single
   error instead of multiple.
2. Fix an error in Sema::ParseDeclarator, where it would crash if the
   declarator didn't have an identifier.  Instead, diagnose the problem.
3. Start adding infrastructure to track the range of locations covered
   by a declspec or declarator.  This is mostly implemented for declspec,
   but could be improved, it is missing for declarator.

Thanks to Neil for pointing out this crash.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@40482 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/switch-duplicate-defaults.c b/test/Sema/switch-duplicate-defaults.c
new file mode 100644
index 0000000..31d46a1
--- /dev/null
+++ b/test/Sema/switch-duplicate-defaults.c
@@ -0,0 +1,10 @@
+// RUN: clang -parse-ast-check %s
+
+void f (int z) { 
+  switch(z) {
+      default:  // expected-error {{first label is here}}
+      default:  // expected-error {{multiple default labels in one switch}}
+        break;
+  }
+} 
+