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/unused-expr.c b/test/Sema/unused-expr.c
new file mode 100644
index 0000000..667f286
--- /dev/null
+++ b/test/Sema/unused-expr.c
@@ -0,0 +1,26 @@
+// RUN: clang -parse-ast-check %s
+
+int foo(int X, int Y);
+
+void bar(volatile int *VP, int *P, int A,
+         _Complex double C, volatile _Complex double VC) {
+  
+  VP == P;             // expected-warning {{expression result unused}}
+  (void)A;             // expected-warning {{expression result unused}}
+  (void)foo(1,2);      // no warning.
+  
+  A == foo(1, 2);      // expected-warning {{expression result unused}}
+
+  foo(1,2)+foo(4,3);   // expected-warning {{expression result unused}}
+
+
+  *P;                  // expected-warning {{expression result unused}}
+  *VP;                 // no warning.
+  P[4];                // expected-warning {{expression result unused}}
+  VP[4];               // no warning.
+
+  // FIXME: SEMA explodes on these.
+  //__real__ C;
+  //__real__ VC;
+}
+