Reword an "expected unqualified-id" error to something more helpful

[rtrieu]

Summary

Currently, "int->get();" or "int.get();" gives the vague error of "expected unqualified-id". The proposed error message is "cannot use arrow operator on a type" or "cannot use dot operator on a type".

[echristo]

*cheers*

-eric

[rtrieu]

r173556

include/clang/Basic/DiagnosticParseKinds.td

 def err_no_matching_param : Error<"parameter named %0 is missing">;
 
 /// C++ parser diagnostics
+def err_invalid_operator_on_type : Error<
+  "cannot use %select{dot|arrow}0 operator on a type">;
 def err_expected_unqualified_id : Error<
   "expected %select{identifier|unqualified-id}0">;
 def err_func_def_no_params : Error<

lib/Parse/ParseDecl.cpp

     if (D.getContext() == Declarator::MemberContext)
       Diag(Tok, diag::err_expected_member_name_or_semi)
         << D.getDeclSpec().getSourceRange();
-    else if (getLangOpts().CPlusPlus)
-      Diag(Tok, diag::err_expected_unqualified_id) << getLangOpts().CPlusPlus;
-    else
+    else if (getLangOpts().CPlusPlus) {
+      if (Tok.is(tok::period) || Tok.is(tok::arrow))
+        Diag(Tok, diag::err_invalid_operator_on_type) << Tok.is(tok::arrow);
+      else
+        Diag(Tok, diag::err_expected_unqualified_id) << getLangOpts().CPlusPlus;
+    } else
       Diag(Tok, diag::err_expected_ident_lparen);
     D.SetIdentifier(0, Tok.getLocation());
     D.setInvalidType(true);

test/Parser/cxx-decl.cpp

   typedef S() : n(1), m(2) { } // expected-error {{function definition declared 'typedef'}}
 };
 
+struct DIE {
+  void foo() {}
+};
+
+void test (DIE die, DIE *Die, DIE INT, DIE *FLOAT) {
+  DIE.foo();  // expected-error {{cannot use dot operator on a type}}
+  die.foo();
+
+  DIE->foo();  // expected-error {{cannot use arrow operator on a type}}
+  Die->foo();
+
+  int.foo();  // expected-error {{cannot use dot operator on a type}}
+  INT.foo();
+
+  float->foo();  // expected-error {{cannot use arrow operator on a type}}
+  FLOAT->foo();
+}
+
 // PR8380
 extern ""      // expected-error {{unknown linkage language}}
 test6a { ;// expected-error {{C++ requires a type specifier for all declarations}} \