On Sep 12, 2013, at 6:35 AM, Mark S. Miller wrote: > On Thu, Sep 12, 2013 at 4:14 AM, Tom Van Cutsem <tomvc...@gmail.com> wrote: > [+markm, allenwb] > > 2013/9/11 David Bruant <bruan...@gmail.com> > Le 11/09/2013 16:22, Tom Van Cutsem a écrit : >> [[GetInheritance]] always checks whether the proxy and target's prototype >> are the same, but as you pointed out, if the target is extensible, you can >> set its prototype to some other object before returning a value from the >> getPrototypeOf trap. > > It's annoying to cleanup post-trap though (to restore the target initial > prototype). Is the invariant on getPrototypeOf that important on extensible > objects? > I think it is the only trap that enforces something without a related eternal > invariant. > > For membranes, when using a shadow target, there's no need to > clean-up/restore anything. > > But more generally, you're right that it's odd [[GetInheritance]] is doing an > invariant check on an otherwise extensible/configurable object. I think it's > simply a remnant of the time before we fully embraced setPrototypeOf. > > agreed > > > Now that Object.setPrototypeOf is part of ES6, there doesn't seem to be a > point in guaranteeing the stability of Object.getPrototypeOf for extensible > objects. > > The important invariant is that getPrototypeOf remain stable for > non-extensible objects. > > Hence, it seems we could replace steps 8-10 of Proxy.[[GetInheritance]] > <https://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-9.3.1> with: > > 8. Let extensibleTarget be the result of IsExtensible(target). > 9. ReturnIfAbrupt(extensibleTarget). > 10. If extensibleTarget is true, then return handlerProto. > // steps below identical to the old steps 8-10: > 11. Let targetProto be the result of calling the [[GetInheritance]] internal > method of target. > 12. ReturnIfAbrupt(targetProto). > 13. If SameValue(handlerProto, targetProto) is false, then throw a TypeError > exception. > > Mark, Allen, does that seem right? > > yes. >
Also, seems right to me. That sounds like sufficient consensus. I'll make the change to the spec. Thanks, Boris Allen
_______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
