Private fields

src/runtime/runtime-classes.cc

Index: src/runtime/runtime-classes.cc
diff --git a/src/runtime/runtime-classes.cc b/src/runtime/runtime-classes.cc
index 5448159513bda41508a1c8cd1f72e859be74197a..62746683b1bf3378ccddaeefd2bf0c2f4116bb16 100644
--- a/src/runtime/runtime-classes.cc
+++ b/src/runtime/runtime-classes.cc
@@ -75,6 +75,20 @@ RUNTIME_FUNCTION(Runtime_ThrowIfStaticPrototype) {
   return *name;
 }
 
+RUNTIME_FUNCTION(Runtime_ThrowIfMissingPrivateField) {

[Dan Ehrenberg, 2016/09/15 21:26:58]

It'd be nice to have a comment somewhere explaining that this runtime function
needs to return the object because it may be used as an LHS

[bakkot, 2016/09/17 00:11:10]

Done.

+  HandleScope scope(isolate);
+  DCHECK(args.length() == 2);
+  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
+  if (!object->IsJSReceiver() ||
+      !JSReceiver::HasOwnProperty(Handle<JSReceiver>::cast(object), name)
+           .FromMaybe(false)) {  // TODO(bakkot) check this doesn't trigger a
+                                 // proxy trap

[Dan Ehrenberg, 2016/09/15 21:26:58]

TODO can be rephrased to say that it in fact doesn't.

Maybe add a DCHECK to ensure that the Name is a private symbol, though.

[bakkot, 2016/09/17 00:11:10]

Done.

+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kMissingPrivateField));
+  }
+  return *object;
+}
 
 RUNTIME_FUNCTION(Runtime_HomeObjectSymbol) {
   DCHECK(args.length() == 0);