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

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 638 matching lines @@
       case LookupIterator::INTEGER_INDEXED_EXOTIC:
         return ReadAbsentProperty(it, language_mode);
       case LookupIterator::DATA:
         return it->GetDataValue();
     }
   }
   return ReadAbsentProperty(it, language_mode);
 }
 
 
+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,
                     LookupIterator::PROTOTYPE_CHAIN_SKIP_INTERCEPTOR);
   return GetDataProperty(&it);
 }
 
 
 Handle<Object> JSReceiver::GetDataProperty(LookupIterator* it) {
   for (; it->IsFound(); it->Next()) {
@@ skipping 16145 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8