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

Erik Arvidsson erik.arvidsson at
Wed Apr 30 10:00:27 PDT 2014

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>

> 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
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