On Nov 7, 2011, at 2:18 AM, Andreas Rossberg wrote:
> On 5 November 2011 17:44, Brendan Eich <bren...@mozilla.com> wrote:
>> Destructuring is "irrefutable" in that it desugars to assignments from
>> properties of the RHS. It is not typed; it is not refutable
>
> I don't think that's true, at least not in the usual sense of
> "irrefutable pattern". Because you can write
>
> let {x} = 666
>
> which will be refuted, by raising a TypeError.
Nope. You get undefined. That's why it's irrefutable -- you can't build
refutable matching on this (you'd need an OOB value other than undefined, or
exceptions).
js> let {x} = 666
js> x
js>
> Of course, the real question is, what does this do:
>
> let {} = 666
No-op. We worked this out for ES4, I had originally made it an early error, but
Lars Hansen argued for the 0-identifier basis case:
js> let {} = 666
js>
This can simplify code generators slightly. It's not a big deal but I agree
with Lars, there should be no error case here.
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