What's the status of Recursive protocol constraints? it's a feature that will help the design of a library I'm working on. How can I help ?
On Tue, Feb 14, 2017 at 1:32 AM Douglas Gregor via swift-evolution < [email protected]> wrote: > > On Feb 13, 2017, at 1:42 PM, Charles Srstka via swift-evolution < > [email protected]> wrote: > > The following comment accompanies the declaration of the SubSequence > associated type in the Collection protocol: > > /// A sequence that represents a contiguous subrange of the collection's > /// elements. > /// > /// This associated type appears as a requirement in the `Sequence` > /// protocol, but it is restated here with stricter constraints. In a > /// collection, the subsequence should also conform to `Collection`. > associatedtype SubSequence : IndexableBase, Sequence = Slice<Self> > > The comments clearly state that the subsequence should conform to > Collection, however, it is not declared as such. Why is this? > > > The compiler doesn’t support “recursive” constraints. We’re working on it > > https://gist.github.com/DougGregor/e7c4e7bb4465d6f5fa2b59be72dbdba6 > > > - Doug > > > _______________________________________________ > swift-evolution mailing list > [email protected] > https://lists.swift.org/mailman/listinfo/swift-evolution >
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