Since you mentioned not finding documentation, here's the new section in "The Swift Programming Language":
Associated Types with a Generic Where Clause https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Generics.html#//apple_ref/doc/uid/TP40014097-CH26-ID557 > On Jul 4, 2017, at 10:53 PM, Xiaodi Wu via swift-evolution > <swift-evolution@swift.org> wrote: > > 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-evolution@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-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
