On Jan 19, 2015, at 12:06 PM, Brendan Eich wrote:
> Why should it throw if there's no [[Get]]?
>
> Consider let {x} = o as short for let x = o.x (with o evaluated once and
> first, in the general case, of course). Then the empty object pattern does
> nothing and should not throw.
>
> This seem best for generated code purposes, it gives a more general basis
> case.
`let { } = x; `
is probably something that should never be written or generated. But consider:
`{x:{ }} = x;` asserts: the RHS must be coercible to an object that has an 'x'
property that is coercible to an object
compared to:
`{x: { }={}} = x;` asserts: the RHS must be coercible to an object and if it
has an 'x' property its value must be coercible to an object
compared to:
`{ } = x` asserts RHS must be coercible to an object
compared to:
`[ ] = x` asserts RHS must be coercible to an Iterable object.
Allen
>
> /be
>
>
>
> Axel Rauschmayer wrote:
>> If I understand the spec correctly, destructuring works as follows:
>>
>> ```js
>> let {} = undefined; // OK???
>> let {x} = undefined; // TypeError
>>
>> let [] = undefined; // TypeError
>> let [y] = undefined; // TypeError
>> ```
>>
>> Destructuring `undefined` (or `null`) via `{}` does not throw an exception
>> (as per first rule inside [1]). Shouldn’t it throw one?
>>
>> Thanks!
>>
>> Axel
>>
>>
>> [1]
>> https://people.mozilla.org/~jorendorff/es6-draft.html#sec-runtime-semantics-destructuringassignmentevaluation
>>
>> <https://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-runtime-semantics-destructuringassignmentevaluation>
>>
>> --
>> Dr. Axel Rauschmayer
>> [email protected] <mailto:[email protected]>
>> rauschma.de
>>
>>
>>
>> _______________________________________________
>> es-discuss mailing list
>> [email protected]
>> https://mail.mozilla.org/listinfo/es-discuss
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asserts: the RHS must be coercible to an object that has an 'x' property that
is coercible to an object
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