The relevant invariant for [[SetPrototypeOf]] is that if the target is non-extensible, and the operation returns "true" (i.e. appears to succeed), then [[GetPrototypeOf]] must return the same result as the value passed into [[SetPrototypeOf]].
This is what I got from the current ES6 draft: < https://people.mozilla.org/~jorendorff/es6-draft.html#sec-proxy-object-internal-methods-and-internal-data-properties-setprototypeof-v > It is always OK for [[SetPrototypeOf]] to return false to indicate reparenting is not possible. Regards, Tom 2013/10/16 Allen Wirfs-Brock <[email protected]> > > On Oct 16, 2013, at 7:25 AM, Mark S. Miller wrote: > > Keep in mind that if an object is non-extensible, its [[Prototype]] cannot > be changed. > > > And objects that are implemented using a Proxy don't use their > [[Prototype]] slot (a Proxy they doesn't have one) or necessarily even > their target's [[Prototype]] to perform lookup of inherited properties. > They can implement inheritance in come completely different manner and > using any internal state they want. The only way I can imagine generalizing > what you are describing is to call the [[SetPrototypeOf]] MOP operation on > the object and even then there is no general guarantee that the request > would be accepted or that it would do what you are imagining. > > Allen > > > > > > On Wed, Oct 16, 2013 at 3:54 AM, Anne van Kesteren <[email protected]>wrote: > >> I believe last time this came up here some people hard concerns so I >> was wondering whether that was still the case and what alternatives >> there might be. >> >> In https://www.w3.org/Bugs/Public/show_bug.cgi?id=20567 we're >> considering to define the behavior Gecko exhibits when moving a node >> between trees in different global objects. >> >> Event handlers and custom elements make this somewhat more tricky and >> we're discussion how to work with them in the bug. >> >> The reason we want to change prototypes is to reduce the potential for >> memory leaks and give consistent behavior across nodes in a tree. I.e. >> they'll always be from the same global. >> >> (There's also the more complicated document.open() scenario, which we >> should discuss separately at some point I think, but for those trying >> to figure out how to define multiple realms in ECMAScript that's worth >> looking into.) >> >> >> -- >> http://annevankesteren.nl/ >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> > > > > -- > Cheers, > --MarkM > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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