Bug 159615 – [ES6] Promise.{all,race} no longer use @@species

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Yusuke Suzuki]

[ES6] Promise.{all,race} no longer use @@species

[Yusuke Suzuki]

Created attachment 283300 [details]
Patch

[Keith Miller]

Comment on attachment 283300 [details]
Patch

r=me. I'm curious what the reasoning behind dropping @@species support was.

[Yusuke Suzuki]

(In reply to comment #2)
> Comment on attachment 283300 [details]
> Patch
> 
> r=me. I'm curious what the reasoning behind dropping @@species support was.

https://github.com/tc39/ecma262/issues/151
https://esdiscuss.org/topic/resolve-reject-on-promise-subclasses-and-species#content-1
https://esdiscuss.org/topic/subclassing-es6-objects-with-es5-syntax#content-50

> Overall consistency in the language. Except for the two offending Promise static methods, all uses of @@species in the ES2015 spec (15 uses) are for the following pattern: Starting from one instance, one constructs a derived object for that instance. (The effective lookup of the @@species property is factored in the SpiecesConstructor and ArraySpeciesCreate abstract operations.)
> 
> Also, in static methods like Promise.all and Promise.race, a constructor is explicitly provided by the user: simply use it. Compare with what is done for arrays:


Seems that Promise.{resolve,reject,all,race} static functions are a factory function while Array#map etc. is an instance method.

[Yusuke Suzuki]

(In reply to comment #3)
In the above comment, this is the quoted part from the es-discuss :)

> > Overall consistency in the language. Except for the two offending Promise static methods, all uses of @@species in the ES2015 spec (15 uses) are for the following pattern: Starting from one instance, one constructs a derived object for that instance. (The effective lookup of the @@species property is factored in the SpiecesConstructor and ArraySpeciesCreate abstract operations.)
> > 
> > Also, in static methods like Promise.all and Promise.race, a constructor is explicitly provided by the user: simply use it. Compare with what is done for arrays:

[Yusuke Suzuki]

Committed r203052: <http://trac.webkit.org/changeset/203052>