Address code review.

Author: qiongsiwu

clang/docs/ReleaseNotes.rst

@@ -675,6 +675,9 @@ Improvements to Clang's diagnostics
       views.push_back(std::string("123")); // warning
     }
 
+- Fixed a bug where Clang hangs on unsupported optional scope specifier ``::`` when parsing
+  Objective-C. Clang now emits a diagnostic message instead of hanging.
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/test/Parser/objc-coloncolon.m

@@ -1,5 +1,13 @@
-// RUN: %clang_cc1 -x objective-c -fsyntax-only -verify %s
+// RUN: %clang_cc1 -x objective-c -fsyntax-only -Wno-objc-root-class -verify %s
+
+int GV = 42;
 
 @interface A
-- (instancetype)init:(::A *) foo; // expected-error {{expected a type}} 
++ (int) getGV;
+- (instancetype)init:(::A *) foo; // expected-error {{expected a type}}
+@end
+
+@implementation A
++ (int) getGV { return ::GV; } // expected-error {{expected a type}}
+- (instancetype)init:(::A *) foo { return self; } // expected-error {{expected a type}}
 @end

clang/test/Parser/objcxx-coloncolon.mm

@@ -0,0 +1,9 @@
+// Test to make sure the parser does not get stuck on the optional
+// scope specifier on the type B.
+// RUN: %clang_cc1 -fsyntax-only %s
+
+class B;
+
+@interface A
+- (void) init:(::B *) foo;
+@end