> On Jan 9, 2018, at 21:39, Brent Royal-Gordon <br...@architechies.com> wrote: > > > >> On Jan 9, 2018, at 4:46 PM, Jordan Rose via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> >> - FWIW I can't actually think of a use case for using this with `if case` or >> anything else. I'm not against it, but I don't know why you would ever do >> it, just like I don't know why you would mix `case #unknown` with `default` >> when matching against a single value. > > if case #unknown = someEnum { > throw MyError.unknownValue > } > …
Yes, you can write that, but why would you do it? What are you going to do below now that you know 'someEnum' is a known value but the compiler doesn't? (Also, it doesn't play well with recompiling…) > >> That said, it sounds like people are happier with `case #unknown` than >> `unknown case`, and that leaves things a little more consistent if we ever >> do expand it to other pattern positions, so I'll change the proposal >> revision to use that spelling. (And if anyone comes up with a nicer >> spelling, great!) > > I don't love the spelling of `#unknown`—particularly since some enums in the > Apple frameworks actually *have* an ordinary case called "unknown"—but I > think it's a nice, pragmatic solution which slots into pattern matching very > nicely. > > (And if we ever *do* decide to support @testable enum parameters, we'll > already have the syntax to specify unknown values.) > > -- > Brent Royal-Gordon > Architechies >
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