[swift-evolution] [swift-evolution-announce] [Review] SE-188 Make stdlib index types Hashable

[Xiaodi Wu]

On Thu, Nov 9, 2017 at 05:28 Brent Royal-Gordon via swift-evolution <
swift-evolution at swift.org> wrote:

> >
> https://github.com/apple/swift-evolution/blob/master/proposals/0188-stdlib-index-types-hashable.md
> >
> > • What is your evaluation of the proposal?
>
> This all seems very sensible, but here's my big question:
>
>         AnyIndex, which type erases any index type at run-time, would not
> be hashable since it might wrap a non-hashable type.
>
> Why not? Specifically, why shouldn't we require `Hashable` conformance on
> indices? Adding it would require changes to conforming types, sure, but
> indices are already required to be `Equatable`, and `Hashable` conformance
> just got really easy to add, and custom `Collection`s are a relatively rare
> and advanced feature.


For a source-breaking change, that’s the wrong question to ask. It’s not
“why not,” but “why so”? It’s so easy to add the conformance, and any type
can opt into it so easily, what is the gain by forcing it and can it be
justified as a source-breaking change?


> Is it worth a source break to add it? Personally, I think so—but even if
> you disagree, I think we should document why we decided not to add it.
>
> > • Is the problem being addressed significant enough to warrant a change
> to Swift?
>
> Yes.
>
> > • Does this proposal fit well with the feel and direction of Swift?
>
> Yes.
>
> > • If you have used other languages or libraries with a similar feature,
> how do you feel that this proposal compares to those?
>
> N/A.
>
> > • How much effort did you put into your review? A glance, a quick
> reading, or an in-depth study?
>
> Quick reading, nothing more.
>
> --
> Brent Royal-Gordon
> Architechies
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20171109/00213268/attachment.html>