d at domenic.me (2015-05-01T13:03:06.086Z)
I don’t think the accessor case does work. `ownDesc` never refers to the property descriptor of the receiver when O[P] is a SuperReference, so if there’s an `this.prop` is an accessor, and `super.prop` doesn’t exist, the data descriptor path is taken.
caitpotter88 at gmail.com (2015-04-21T01:53:32.508Z)
>>If the prop property accessed by super.prop is an accessor, super.prop = x; should invoke its setter. super.prop should invoke its getter.
>It does. This is about what happens when that property is a data property doesn't exist. What happens when we do [[HomeObject]].[[GetPrototypeOf]]().[[Set]]('prop', x, this)
I don’t think the accessor case does work. `ownDesc` never refers to the property descriptor of the receiver when O[P] is a SuperReference, so if there’s an `this.prop` is an accessor, and `super.prop` doesn’t exist, the data descriptor path is taken.
>>If the prop property accessed by super.prop is an accessor, super.prop = x; should invoke its setter. super.prop should invoke its getter. >It does. This is about what happens when that property is a data property doesn't exist. What happens when we do [[HomeObject]].[[GetPrototypeOf]]().[[Set]]('prop', x, this) I don’t think the accessor case does work. `ownDesc` never refers to the property descriptor of the receiver when O[P] is a SuperReference, so if there’s an `this.prop` is an accessor, and `super.prop` doesn’t exist, the data descriptor path is taken. > On Apr 20, 2015, at 9:37 PM, Allen Wirfs-Brock <allen at wirfs-brock.com> wrote: > > > On Apr 20, 2015, at 6:21 PM, Mark Miller wrote: > >> If the prop property accessed by super.prop is an accessor, super.prop = x; should invoke its setter. super.prop should invoke its getter. > > It does. This is about what happens when that property is a data property doesn't exist. What happens when we do [[HomeObject]].[[GetPrototypeOf]]().[[Set]]('prop', x, this) > > Allen > > > > > > > > > >> >> On Tue, Apr 21, 2015 at 4:18 AM, Allen Wirfs-Brock <allen at wirfs-brock.com <mailto:allen at wirfs-brock.com>> wrote: >> >> On Apr 20, 2015, at 12:39 PM, Jason Orendorff wrote: >> >>> On Mon, Apr 20, 2015 at 12:44 PM, Allen Wirfs-Brock >>> <allen at wirfs-brock.com <mailto:allen at wirfs-brock.com>> wrote: >>>>> In the spec, 9.1.9 step 4.d.i. is where `super.prop = 2` ends up, with >>>>> O=X.prototype. >>>> >>>> 4.d.1 doesn't set the property, it just comes up with the property descriptor to use, if the `Receiver` does not already have a corresponding own property. >>>> >>>> 5.c+5.e checks if the corresponding own property actually exists on the `Receiver`. >>>> >>>> If it already exits then it does a [[DefineOwnProperty]] that only specifies the `value` attribute. This should respect the current `writable` attribute of the property and hence reject the attempt to change the value. >>> >>> I agree with all of this, except I don't see where the attempt is >>> rejected. Since the property is configurable, I think >>> [[DefineOwnProperty]] succeeds. >>> >>> The property is still non-writable afterwards. Only the value changes. >>> >>> So this isn't breaking the object invariants: the property in question >>> is configurable, so it's OK (I guess) to change the value. It's just >>> surprising for assignment syntax to succeed in doing it. >> >> I think it's bogus and needs to be corrected. Not only does it allow (in weird cases for [[Set]] (ie, assignment) to change the value of a non-writable property. It also means there are cases where [[Set]] will convert an accessor property to a data property. >> >> In combination, I think this is a serious bug that needs to be fix in the final published ES6 spec. The fix I propose is in 9.1.9 to replace Set 5.e as follows: >> >> 5.e If existingDescriptor is not undefined, then >> i. If IsAccessorDescript(existingDescript), return false. >> ii. If existingDescriptor.[[Writable]] is false, return false. >> iii. Let valueDesc be the PropertyDescriptor{[[Value]]: V}. >> iv. Return Receiver.[[DefineOwnProperty]](P, valueDesc). >> >> Lines 5.e.i and 5.e.ii are new additions. >> >> Thoughts? >> Allen >> >> >> _______________________________________________ >> es-discuss mailing list >> es-discuss at mozilla.org <mailto:es-discuss at mozilla.org> >> https://mail.mozilla.org/listinfo/es-discuss <https://mail.mozilla.org/listinfo/es-discuss> >> >> >> >> >> -- >> Text by me above is hereby placed in the public domain >> >> Cheers, >> --MarkM > > _______________________________________________ > es-discuss mailing list > es-discuss at mozilla.org > https://mail.mozilla.org/listinfo/es-discuss -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20150420/b8843d8a/attachment.html>