Replying to swift-users as well, as it's probably the more appropriate forum.
SE-0142 (Permit where clauses to constrain associated types) is what brought about this feature. It is now used in the standard library. On Wed, Jul 5, 2017 at 00:26 Jens Persson via swift-evolution < swift-evolut...@swift.org> wrote: > The following compiles in Swift 4 (but not in Swift 3.1): > > protocol P1 { > associatedtype A > } > protocol P2 : P1 where A == Int { > } > > I've not been able to find any proposal, discussion or documentation > mentioning it so any pointers to such would be greatly appreciated. > > Also, is this new feature used somewhere in the std lib? > > /Jens > _______________________________________________ > swift-evolution mailing list > swift-evolut...@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution >
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