ES6 Unscopables

src/contexts.cc

Index: src/contexts.cc
diff --git a/src/contexts.cc b/src/contexts.cc
index cb5e852d7d669c07c8d8b950016defff1572f49c..53851db7b61dc0bfd1ff95af04934f9761dc679b 100644
--- a/src/contexts.cc
+++ b/src/contexts.cc
@@ -71,6 +71,50 @@ void Context::set_global_proxy(JSObject* object) {
 }
 
 
+static PropertyAttributes GetWithContextAttributes(Isolate* isolate,
+                                                   Handle<String> name,
+                                                   Handle<JSReceiver> object) {
+  Handle<Symbol> unscopables_symbol(
+      isolate->native_context()->unscopables_symbol(), isolate);
+
+  while (true) {
+    PropertyAttributes name_attrs =
+        JSReceiver::GetOwnPropertyAttributes(object, name);
+
+    if (name_attrs != ABSENT) {
+      PropertyAttributes unscopables_attrs =
+          JSReceiver::GetOwnPropertyAttributes(object, unscopables_symbol);
+      PropertyAttributes blocked_attrs = ABSENT;
+      if (unscopables_attrs != ABSENT) {
+        Handle<Object> unscopables_object;
+        ASSIGN_RETURN_ON_EXCEPTION_VALUE(
+            isolate, unscopables_object,
+            Object::GetProperty(object, unscopables_symbol), name_attrs);
+
+        if (unscopables_object->IsSpecObject()) {
+          blocked_attrs = JSReceiver::GetOwnPropertyAttributes(
+              Handle<JSReceiver>::cast(unscopables_object), name);
+        }
+      }
+
+      if (blocked_attrs == ABSENT) {
+        return name_attrs;
+      }
+    }
+
+    Object* prototype = object->GetPrototype();
+    if (prototype->IsNull()) {
+      return ABSENT;
+    }
+    ASSERT(prototype->IsSpecObject());
+    object = handle(JSReceiver::cast(prototype), isolate);
+  }
+
+  UNREACHABLE();
+  return ABSENT;
+}
+
+
 Handle<Object> Context::Lookup(Handle<String> name,
                                ContextLookupFlags flags,
                                int* index,
@@ -109,9 +153,12 @@ Handle<Object> Context::Lookup(Handle<String> name,
       if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0 ||
           object->IsJSContextExtensionObject()) {
         *attributes = JSReceiver::GetOwnPropertyAttributes(object, name);
+      } else if (FLAG_harmony_unscopables && context->IsWithContext()) {
+        *attributes = GetWithContextAttributes(isolate, name, object);
       } else {
         *attributes = JSReceiver::GetPropertyAttributes(object, name);
       }
+
       if (isolate->has_pending_exception()) return Handle<Object>();
 
       if (*attributes != ABSENT) {