Perhaps @@unscopable shouldn't be a Set...

[Erik Arvidsson]

On Wed, Apr 30, 2014 at 5:17 PM, Allen Wirfs-Brock <allen at wirfs-brock.com>wrote:

> Where do you find the spec incomplete WRT @@unscopable.  My recollection
> was that it was all resolved and fully specified and that I was relatively
> happy with the outcome.
>

I thought so too but now that I look at it I cannot find where we Get the
@unscopable list out of the with expression object. As far as I can
tell unscopables is never populated.

http://people.mozilla.org/~jorendorff/es6-draft.html#sec-with-statement-runtime-semantics-evaluation
http://people.mozilla.org/~jorendorff/es6-draft.html#sec-newobjectenvironment


>
> Allen
>
> On May 1, 2014, at 3:00 AM, Erik Arvidsson <erik.arvidsson at gmail.com>
> wrote:
>
> This was never resolved and the spec is incomplete here
>
> On Wed Sep 25 2013 at 6:17:32 PM, Allen Wirfs-Brock <allen at wirfs-brock.com>
> wrote:
>
>> So here is another concern, about the scheme we agreed to last week.
>>
>> It needs to match a found own property against the possibility of an own
>> @@unscopable property on the same object and that  object may be somewhere
>> up the inheritance chain of the actual with object.  The means that
>> [[HasProperty]]/[[Get]]/[[Set]] can not be used to do those resolve
>> binding in an ObjectEnvironmentRecord because they don't tell us where the
>> property was found.  Instead, ObjectEnvironmentRecord needs to reimplement
>> its own property lookup using [[GetOwnProperty]] and [[GetInheritanceOf]].
>>  However, if the with object is a proxy that means we may be bypassing the
>> actual inheritance mechanism implemented by the Proxy's 'has'/'get'/'set'
>> traps and that could introduce observable semantics irregularities.
>>
>> Specifying the duplicated lookup is doable but a pain.  That and the
>> semantic issues WRT proxies makes me a lot less comfortable with the added
>> complexity of supporting @@unscopable.
>>
>> Allen
>
>
>


-- 
erik
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