Le 12/09/2013 15:35, Mark S. Miller a écrit :
On Thu, Sep 12, 2013 at 4:14 AM, Tom Van Cutsem <[email protected]
<mailto:[email protected]>> wrote:
[+markm, allenwb]
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.
Based on this new fresh agreement and assuming it sticks, the answer to
Boris initial question changes a bit then:
if B.isPrototypeOf(A) and A' = new Proxy(A, handler), then the
handler.getPrototypeOf can return any object (including B', a
membrane-proxy to B) as long as A is extensible. If the code that runs
against your membrane is not expected to be allowed to change
extensiveness, you don't need a shadow target.
David
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