Computed Property Name Shorthand Proposal

[Jeremy Martin]

I'm usually lousy at interpreting the spec (yet here I go!), but I think
the behavior is explained here [1]:

PropertyDefinition[Yield] :
    IdentifierReference[?Yield]
    CoverInitializedName[?Yield]
    PropertyName[?Yield] : AssignmentExpression[In, ?Yield]
    MethodDefinition[?Yield]

PropertyName[Yield,GeneratorParameter] :
    LiteralPropertyName
    [+GeneratorParameter] ComputedPropertyName
    [~GeneratorParameter] ComputedPropertyName[?Yield]

LiteralPropertyName :
    IdentifierName
    StringLiteral
    NumericLiteral

ComputedPropertyName[Yield] :
    [ AssignmentExpression[In, ?Yield] ]

There are aspects to that grammar that I don't fully grok yet, but your `{
[foo] }` example appears to be trying to combine the `IdentifierReference`
form (which *doesn't support* an `AssignmentExpression`) and the `PropertyName:
AssignmentExpression` form (which *requires* the `AssignmentExpression`).

In other words, all paths in that grammar that lead to a `
ComputedPropertyName` being valid also require the right-hand `
AssignmentExpression`.

[1]
http://people.mozilla.org/~jorendorff/es6-draft.html#sec-object-initializer


On Thu, Aug 27, 2015 at 12:25 PM, Kevin Smith <zenparsing at gmail.com> wrote:

> I'd expect the following to work, given that the prop expression evaluates
>> to 'bar', and bar is in context.
>>
>> var foo = 'bar'
>> var bar = 'ponyfoo'
>> var baz = { [foo] }
>> console.log(baz)
>> // <- { bar: 'ponyfoo' }
>>
>
> Hmmm...  I'm not sure I would expect any such thing.  It seems like you're
> proposing some kind of dynamic eval-ish variable binding lookup, which is
> probably going to be a no-go.
>
> Kevin
>
>
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-- 
Jeremy Martin
661.312.3853
http://devsmash.com
@jmar777
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