ES6 Unscopables

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index abd018770bbcaf37dbf552ea06ebfa6d7cc92f13..b095a63d296ba138f7a3b730152cd744343a0074 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -129,7 +129,8 @@ void Object::Lookup(Handle<Name> name, LookupResult* result) {
 }
 
 
-MaybeHandle<Object> Object::GetProperty(LookupIterator* it) {
+MaybeHandle<Object> Object::GetPropertyHelper(
+    LookupIterator* it, bool force_holder_as_receiver_for_accessor_callback) {
   for (; it->IsFound(); it->Next()) {
     switch (it->state()) {
       case LookupIterator::NOT_FOUND:
@@ -150,10 +151,18 @@ MaybeHandle<Object> Object::GetProperty(LookupIterator* it) {
       case LookupIterator::PROPERTY:
         if (it->HasProperty()) {
           switch (it->property_kind()) {
-            case LookupIterator::ACCESSOR:
-              return GetPropertyWithAccessor(
-                  it->GetReceiver(), it->name(),
-                  it->GetHolder(), it->GetAccessors());
+            case LookupIterator::ACCESSOR: {
+              Handle<Object> accessors = it->GetAccessors();
+              Handle<Object> receiver;
+              if (force_holder_as_receiver_for_accessor_callback &&
+                  !accessors->IsAccessorPair()) {
+                receiver = it->GetHolder();
+              } else {
+                receiver = it->GetReceiver();
+              }
+              return GetPropertyWithAccessor(receiver, it->name(),
+                                             it->GetHolder(), accessors);
+            }

[Toon Verwaest, 2014/07/23 12:08:38]

Euh, no.

What you want to do is fix a bug in Array.length; but what you do instead is
modify get-property to change the semantics of all API accessors...

The right fix is to change ArrayLengthGetter to not use This() (via
GetThisFrom), but rather read the value from the Holder(). That also removes the
need for FindInstanceOf.

             case LookupIterator::DATA:
               return it->GetDataValue();
           }
@@ -165,6 +174,19 @@ MaybeHandle<Object> Object::GetProperty(LookupIterator* it) {
 }
 
 
+MaybeHandle<Object> Object::GetProperty(LookupIterator* it) {
+  return GetPropertyHelper(it, false);
+}
+
+
+MaybeHandle<Object> Object::GetPropertyForUnscopables(LookupIterator* it) {
+  // TODO(arv): For unscopables we need to make sure that we use the holder as
+  // the receiver for data properties that are implemented as callbacks
+  // (ACCESSER && !IsAccessorPair).
+  return GetPropertyHelper(it, true);
+}
+
+
 bool Object::ToInt32(int32_t* value) {
   if (IsSmi()) {
     *value = Smi::cast(this)->value();