[es6] silence access-check failure for well-known symbol properties

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 2e60cf0982ed3ce6947af92d8c973a289f0e80e4..56d2ec1c41522439eb87da255bb7a8d3db51b12b 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -994,6 +994,14 @@ MaybeHandle<Object> JSObject::GetPropertyWithFailedAccessCheck(
                                GetPropertyWithInterceptor(it, &done), Object);
     if (done) return result;
   }
+  if (!it->IsElement()) {

[Toon Verwaest, 2015/10/02 08:05:27]

Rather than if (!it->IsElement()) etc, you can just use
Handle<Name> name = it->GetName();
if (name->IsSymbol() && Symbol::cast(*name)->is_well_known_symbol()) {
  return it->factory()->undefined_value();
}

[caitp (gmail), 2015/10/02 10:01:15]

GetName() converts elements to strings, which isn't needed, but name() has a
DCHECK(!IsElement()). So, it seemed better to avoid the allocation, from my pov.

I can change it if people prefer that

[Toon Verwaest, 2015/10/02 10:07:01]

That is possibly true. It could already have been cached. Adding IsElement()
only avoids this possible cost (in an exceptional path that's not performance
sensitive), but does introduce extra unnecessary complexity here.

[caitp (gmail), 2015/10/02 10:41:56]

Done.

+    Handle<Name> name = it->name();
+    if (name->IsSymbol() &&
+        Handle<Symbol>::cast(name)->is_well_known_symbol()) {
+      RETURN_EXCEPTION_IF_SCHEDULED_EXCEPTION(it->isolate(), Object);

[Toon Verwaest, 2015/10/02 08:05:27]

I don't see why this statement (RETURN_EX..) is needed.

[caitp (gmail), 2015/10/02 10:01:15]

I guess it isn't really needed, will remove

[caitp (gmail), 2015/10/02 10:41:56]

Done.

+      return it->factory()->undefined_value();
+    }
+  }
   it->isolate()->ReportFailedAccessCheck(checked);
   RETURN_EXCEPTION_IF_SCHEDULED_EXCEPTION(it->isolate(), Object);
   return it->factory()->undefined_value();