what if OneOf<A, A>? duplicate variable compile warning?
> 在 2016年7月1日，20:59，Adrian Z. <[email protected] > <mailto:[email protected]>> 写道： > > Just one simple thing to add: > > If ...T equals 10 then <...T, U> = 10 + 1 = 11 types > If ...U equals 17 then <T, ...U> = 1 + 17 = 18 types > If ...T equals 20 and ...Uequals 22 then <...T, ...U> = 20 + 22 = 42 types > — > You are receiving this because you were mentioned. > Reply to this email directly, view it on GitHub > <https://github.com/apple/swift-evolution/pull/404#issuecomment-229940122>, > or mute the thread > <https://github.com/notifications/unsubscribe/ABsfmhH9yasaWK8vAs17DGXWHV54QuCkks5qRQ9KgaJpZM4JC7-2>. > >> > >> 在 2016年7月1日，21:33，Cao Jiannan <[email protected]> 写道： >> >> I can't compile your code. I'm really not sure your code will pass the >> complex generic check 🙃 >> >> Union version more complex or generic version? >> I think union version is more normal. >>> For example: >>> >>> typealias ABC = A | B | C >>> >>> typealias ABCD = ABC | D >>> >>> we just use an existed type ABC to construct ABCD >>> >>> But how about generic wrap? >>> >>> Bikeshedding: >>> >>> // we generate the boundary with `A | B` or directly OneOf<A, B> >>> enum OneOf<...T> { >>> >>> ...case $#(T) >>> >>> // Bikeshedding variadic enum casses: >>> // we might need an index to set the value? >>> init(index: Int, value: T) { >>> >>> self = .$index(value) >>> } >>> } >>> >>> /// Usage: >>> /// A | B | C == OneOf<A, B, C> >>> func |<T, U>(_: T.Type, _: U.Type) -> OneOf<T, U>.Type { >>> >>> // I believe the usage of `type` like this was prposed by Joe Groff >>> // I also use the proposal to remove `.self` magic here >>> return OneOf<T, U> >>> } >>> >>> // Here is how to merge OneOf into a single dimension >>> func |<...T, U>(_: OneOf<...T>.Type, _: U.Type) -> OneOf<...T, U>.Type { >>> >>> // Copy and merge types into the new `OneOf` type >>> return OneOf<...T, U> >>> } >>> >>> func |<T, ...U>(_: T.Type, _: OneOf<...U>.Type) -> OneOf<T, ...U>.Type { >>> >>> // Copy and merge types into the new `OneOf` type >>> return OneOf<T, ...U> >>> } >>> >>> func |<...T, ...U>(_: OneOf<...T>.Type, _: OneOf<...U>.Type) -> OneOf<...T, >>> ...U>.Type { >>> >>> // Copy and merge types into the new `OneOf` type >>> return OneOf<...T, ...U> >>> } >>> Your example will become: >>> >>> typealias ABC = A | B | C // or OneOf<A, B, C> >>> typealias ABCD = ABC | D // merging lhs OneOf with D to OneOf<A, B, C, D> >>> Mission accomplished. >>> >>> >>>> 在 2016年7月1日，17:06，Cao Jiannan <[email protected] <mailto:[email protected]>> >>>> 写道： >>>> >>>> https://github.com/frogcjn/swift-evolution/blob/master/proposals/xxxx-union-type.md >>>> >>>> <https://github.com/frogcjn/swift-evolution/blob/master/proposals/xxxx-union-type.md> >>>> >>>> Hi, >>>> >>>> I'm now officially proposal the union type feature for Swift. Please see: >>>> >>>> >>>> https://github.com/apple/swift/commit/eb7311de065df7ea332cdde8782cb44f9f4a5121 >>>> >>>> <https://github.com/apple/swift/commit/eb7311de065df7ea332cdde8782cb44f9f4a5121> >>>> Introduction >>>> >>>> Add union type grammar, represents the type which is one of other types. >>>> >>>> var stringOrURL: String | URL = "https://www.apple.com >>>> <https://www.apple.com/>" >>>> >>>> >>>> I would be thankful if someone support this idea and give some advice. >>>> Thanks! >>>> >>>> >>>> -- >>>> Jiannan >>>> >>>> >>> >
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