> On Jun 14, 2017, at 4:51 PM, David Hart via swift-evolution > <swift-evolution@swift.org> wrote: > > >> On 14 Jun 2017, at 22:37, Vladimir.S via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> >> On 14.06.2017 21:23, Haravikk via swift-evolution wrote: >>>> On 14 Jun 2017, at 19:08, Xiaodi Wu via swift-evolution >>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org> >>>> <mailto:swift-evolution@swift.org <mailto:swift-evolution@swift.org>>> >>>> wrote: >>>> >>>> On Wed, Jun 14, 2017 at 1:01 PM, David Hart via swift-evolution >>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org> >>>> <mailto:swift-evolution@swift.org <mailto:swift-evolution@swift.org>>> >>>> wrote: >>>> >>>> Sorry, initially sent off-list: >>>> >>>> I think this proposal is a great idea. But I would vote for the >>>> alternative of >>>> only having default and implicitly deducing extend when default is not >>>> specified: >>>> >>>> >>>> This wouldn't work with the fundamental design decision that these are >>>> optional keywords, which IMO is absolutely key. >> >>> Hmm, I'm inclined to agree with David that only the default keyword really >>> seems like it's necessary, and that extend can be implied. >> … > > I think a good plan would be to make default required in a later Swift > version (Swift 5) for example, and only warn for now.
I like only having “default,” and I like David’s plan for achieving that. • • • It seems that this proposal could help mitigate the problems described in the classic “Ghost of Swift Bugs Future” (https://nomothetis.svbtle.com/the-ghost-of-swift-bugs-future <https://nomothetis.svbtle.com/the-ghost-of-swift-bugs-future>). There’s a nice new convention (I think?) of: `extend` / no modifier in extension → static dispatch `default` in extension → dynamic dispatch (Does this always hold in an extensions?) Knowing whether the extension’s author •intended• static or dynamic dispatch could also allow the compiler to give better warnings: about shadowing at declaration sites, and also also potentially at call sites where multiple extension methods could match depending on the compile-time type of the receiver. Might it be worth describing some of these warnings out in the proposal? I realize warnings don’t require full swift-evo treatment, but it would be nice to at least sketch out in the “Impact on Existing Code” section what the warnings might look like. Cheers, Paul
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