> On May 20, 2016, at 11:34 AM, Jordan Rose via swift-evolution > <[email protected]> wrote: > >> >> On May 20, 2016, at 10:25, John McCall <[email protected] >> <mailto:[email protected]>> wrote: >> >>> On May 19, 2016, at 4:13 PM, Jordan Rose via swift-evolution >>> <[email protected] <mailto:[email protected]>> wrote: >>>> On May 14, 2016, at 22:16, Chris Lattner via swift-evolution >>>> <[email protected] <mailto:[email protected]>> wrote: >>>> >>>> On May 13, 2016, at 9:16 AM, Joe Groff via swift-evolution >>>> <[email protected] <mailto:[email protected]>> wrote: >>>>>> This encourages the use of empty closures over optional closures, which >>>>>> I think is open for debate. In general I try to avoid optionals when >>>>>> they can be precisely replaced with a non-optional value. Furthermore, >>>>>> most Cocoa completion handlers are not optional. >>>>>> >>>>>> The alternative is to not do this, but encourage that any closure that >>>>>> could reasonably be empty should in fact be optional. I would then want >>>>>> Cocoa functions with void-returning closures to be imported as optionals >>>>>> to avoid "{ _ in }". >>>>> >>>>> +1. In general, I think we should allow implicit arguments, without >>>>> requiring the closure to use all the implicit $n variables like we do >>>>> today. These should all be valid: >>>>> >>>>> let _: () -> () = {} >>>>> let _: (Int) -> () = {} >>>>> let _: (Int, Int) -> Int = { 5 } >>>>> let _: (Int, Int) -> Int = { $0 } >>>>> let _: (Int, Int) -> Int = { $1 } >>>> >>>> I agree, but I consider this to be an obvious bug in the compiler. I >>>> don’t think it requires a proposal. >>> >>> Sorry to find this thread late. I don’t think this is just a bug; it’s also >>> a way to check that a parameter isn’t getting forgotten. For a >>> single-expression closure that’s probably overkill, but maybe we’d keep the >>> restriction for multi-statement closures? >> >> The bug we're talking about is that closures have to have a reference to $n >> when there are n+1 parameters. > > Oh, I completely forgot that it’s only $n you have to reference, not $n-1 or > anything else. So I guess it’s not quite serving the purpose I thought it was. > > Jordan
Who knew? http://i.imgur.com/8ytNkn0.jpg <http://i.imgur.com/8ytNkn0.jpg> ! So anyway, how hard a problem is this to fix? And do you want me to submit the proposal as a PR or not? -- E
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