On Jan 3, 2012, at 3:27 PM, Brendan Eich wrote:
> You're proposing that we require 'let' be only at the start of statements? If
> so, then destructuring is problematic:
>
> foo();
> let [x] = y;
>
> Did that last line destructure the property named '0' of the object denoted
> by y into a let-bound x, or was it old, pre-ES6 code that stored y into the
> x'th element of an object denoted 'let'? In either case the 'let' is at the
> start of a statement.
>
> /be
Based on the draft of the spec I have, I don't think that is an actual
ambiguity here (albeit naming an array 'let' could be very confusing!).
This could of course either be an error in my reading of the spec, or a bug in
the current draft of the grammar. :-)
The rules for destructuring give:
ArrayBindingPattern :
[ Elision<opt> BindingRestElement<opt> ]
[ BindingElementList , Elision<opt> BindingRestElement<opt> ]
Note the literal comma required after any BindingElementList - as I parse the
grammar your example is not valid ES6, to destructure the first element from an
array you would have to write:
foo();
let [x,] = y;
As such, the example you give could only be storing y to a property x of object
let (or a syntax error in ES5-strict / ES6 modes).
Is my reading of the spec incorrect here? Is this the intention?
cheers,
G.
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