[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..3412197f1d16da570a90e84c262b9b71717022d2 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -656,6 +656,43 @@ MaybeHandle<Object> Object::GetProperty(LookupIterator* it,
 }
 
 
+MaybeHandle<Object> Object::GetPropertyEx(LookupIterator* it,
+                                          bool& access_check_failed,
+                                          LanguageMode language_mode) {
+  access_check_failed = false;

[caitp (gmail), 2015/10/01 15:16:47]

This alternative implementation doesn't change the nature of [[Get]] in general,
but provides an alternative way of getting properties when special behaviour is
required in the case of access checks.

This duplicates some code, and the method name isn't very good. But I think this
is more general and applies to other well-known Symbols (eg if something special
is done for @@toStringTag instead of treating it as undefined --- not spec'd yet
but it sounds like it's a possibility?).

What are peoples thoughts?

+  for (; it->IsFound(); it->Next()) {
+    switch (it->state()) {
+      case LookupIterator::NOT_FOUND:
+      case LookupIterator::TRANSITION:
+        UNREACHABLE();
+      case LookupIterator::JSPROXY:
+        return JSProxy::GetPropertyWithHandler(
+            it->GetHolder<JSProxy>(), it->GetReceiver(), it->GetName());
+      case LookupIterator::INTERCEPTOR: {
+        bool done;
+        Handle<Object> result;
+        ASSIGN_RETURN_ON_EXCEPTION(
+            it->isolate(), result,
+            JSObject::GetPropertyWithInterceptor(it, &done), Object);
+        if (done) return result;
+        break;
+      }
+      case LookupIterator::ACCESS_CHECK:
+        if (it->HasAccess()) break;
+        access_check_failed = true;
+        return it->isolate()->factory()->undefined_value();
+      case LookupIterator::ACCESSOR:
+        return GetPropertyWithAccessor(it, language_mode);
+      case LookupIterator::INTEGER_INDEXED_EXOTIC:
+        return ReadAbsentProperty(it, language_mode);
+      case LookupIterator::DATA:
+        return it->GetDataValue();
+    }
+  }
+  return ReadAbsentProperty(it, language_mode);
+}
+
+
 Handle<Object> JSReceiver::GetDataProperty(Handle<JSReceiver> object,
                                            Handle<Name> name) {
   LookupIterator it(object, name,