Regardless of whether or not you agree, that was the original motivation for its introduction.
From: [email protected] [mailto:[email protected]] On Behalf Of C. Scott Ananian Sent: Wednesday, June 10, 2015 11:45 To: Domenic Denicola Cc: Allen Wirfs-Brock; Mark S. Miller; es-discuss list Subject: Re: Fixing `Promise.resolve()` I don't agree that @@species is useful at all for changing constructor signatures, since there is no closure argument. If we had dynamically scoped variables, then: ``` LabelledPromise[Symbol.species] = function() { return LabelledPromise.bind(label/*dynamically scoped*/); }; function() { let label = "foo"; return LabelledPromise.resolve(x); } ``` would indeed be very interesting. But in the absence of some sort of closure, the only way you can make @@species into a custom constructor is for odd special cases where you are just rearranging deck chairs. Why not: ``` class LabelledPromise { constructor(exec, label) { super(exec); this.label = label === undefined ? "<derived promise>" : label; } } ``` --scott
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