1171053 - Function.prototype.bind: Bound functions must use the [[Prototype]] of their target function instead of Function.prototype

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Claude Pache]

A function object constructed using Function#bind must retain the [[Prototype]] of its target function.
Currently, it gets the default one, namely Function.prototype.

This is a breaking change introduced in ES6.

For the reference, see steps 2 and 8 of BoundFunctionCreate() in the spec:
https://people.mozilla.org/~jorendorff/es6-draft.html#sec-boundfunctioncreate

For the justification, see https://bugs.ecmascript.org/show_bug.cgi?id=3819#c0

Here is a test case:

```
function getProtoBound(proto) {
    var f = Object.setPrototypeOf(function() { }, proto)
    var boundF = Function.prototype.bind.call(f, null)
    return Object.getPrototypeOf(boundF)
}

for (var proto of [ Function.prototype, function(){}, [], null ]) {
    console.log(Object.is(getProtoBound(proto), proto)) // should always log true
}
```

Comment 1

[Tom S. (please needinfo tschuster)]

Attachment: Remove JS_BindCallable

This function doesn't have any uses and makes the code somewhat more complex.

Comment 2

[Eric Faust [:efaust]]

Comment on attachment 8627256 [details] [diff] [review]
Remove JS_BindCallable

Review of attachment 8627256 [details] [diff] [review]:
-----------------------------------------------------------------

Oh, cool. I didn't realize this was dead. Rock.

Comment 3

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/1d3fa54d5eb9

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/1d3fa54d5eb9

Comment 5

[Tom S. (please needinfo tschuster)]

This was fixed by bug 1055472 patch part 3.