On Wed, Jul 11, 2012 at 1:06 PM, Brendan Eich <[email protected]> wrote:
> Russell Leggett wrote: > >> >> >> >> Russell asked about 'length' -- per a previous thread, I thought >> we agreed that one [[Get]] of 'length' would be done before >> matching if and only if the array literal contains a spread >> (covering rest, the dual for a pattern of spread in the array >> literal corresponding to the pattern). >> >> >> Yes, I saw this in the proposal algorithm. The reason I ask is because it >> seems odd to have an additional structural requirement in some cases but >> not others. Of course, I understand why, but it sort of makes it look like >> [] implies additional array-like structure in one case, but not in another. >> > > You get what you ask for. Pay as you go. Buy by the yard. > > Ok, out of clichés but I hope we aren't going to revisit and impose a > mandatory [[Get]] of 'length' on all array destructuring forms. That is > otiose and costly (potentially very). > > The presence of ...rest is static syntax, so there's no runtime > maybe/maybe-not hazard. It would not have to be a [[Get]] of 'length', just a check for its existence. Its no deal breaker for me, but it seemed a little inconsistent. We could also be more strict with an Array.isArray check, but that seems too strict. Anyway, just a thought. - Russ > > > /be >
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