[Webkit-unassigned] [Bug 26382] [ES5] Implement Function.prototype.bind

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=26382





--- Comment #29 from Mark S. Miller <erights at gmail.com>  2011-04-28 09:35:16 PST ---
(In reply to comment #25)
> 
> JS can reasonably emulate the [[Call]] behavior of .bind() but not 
> its [[Construct]] behavior. This is important because the [[Construct]] 
> behavior of .bind() is the only way to implement a correct var-args 
> construction (new) operation in ES5.

To expand on that, given the ES5 specified Function.prototype.bind, one can implement a "construct(f, args)" operation as follows:

    > function construct(f, args) {
    >   var bound = Function.prototype.bind.apply(f, [null].concat(args));
    >   return new bound();
    > }

    > construct(Date, [1957, 5, 27])
    Thu Jun 27 1957 00:00:00 GMT-0700 (PDT)

Without the specified primitive implementation of bind, I know of no way for a pure JavaScript shim to correctly emulate this behavior, and therefore no way for an ES-next to ES5 compiler to correctly compile "new f(...args)" to ES5.

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