New ES6 draft now available

Allen Wirfs-Brock allen at wirfs-brock.com
Mon Nov 26 10:24:34 PST 2012


On Nov 26, 2012, at 9:44 AM, Tom Van Cutsem wrote:

> 2012/11/25 Allen Wirfs-Brock <allen at wirfs-brock.com>
> 
> On Nov 25, 2012, at 12:41 PM, Tom Van Cutsem wrote:
>> 
>> However, with [[HasProperty]] removed, I assume the "in"-operator no longer triggers the "has" trap when it encounters a proxy, instead doing the proto-chain-walk itself and calling "hasOwn" on each level. This is OK, although it introduces an inconsistency with the other proto-chain-walking algorithms, which stop when encountering a proxy, letting the proxy take over from that point (this is the case for the "get", "set" and "enumerate" traps).
> 
> [[HasProperty]] is replaced with a HasProperty abstract operation (9.3.6) that indeed makes generic calls to [[HasOwnProperty]] and [[GetInheritance]]  in a loop.  This also slightly bothers me. I guess I convinced my self that an object that wanted to use a non-standard inheritance path could hide that by reporting its inherited properties to be own properties.
> 
> I also occasionally find it troubling  inheritance semantics are replicated in three different places [[GetP]], [[SetP]], and HasProperty and that it is quite possible to get them out of sync.   I've come to accept the replication/possible inconsistency but maybe we really do need to bring back [[HasProperty]] so that it is possible to consistently over-ride all three.  I'd might be happy to swap [[Feeze]]/[[Seal]]/i[[sFrozen]]/[[isSealed]] for [[HasProperty]]  :-)
> 
> Yes, this is a good point: one must be able to consistently override all inheritance-related operations. Requiring an object with multiple prototypes to report all inherited properties as "own" feels broken.
> 
> W.r.t. freeze and friends, I thought you were considering a more generic [[GetIntegrity]]/[[SetIntegrity]] operation.

Yes, are you on board with that?






> 
> Cheers,
> Tom

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