<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div>It's pretty bizarre that conforming to `protocol P: Q {}` requires an explicit conformance to Q when Q is a class but not when Q is a protocol. It's the same syntax, but conformance is only "inherited" for protocols.</div><div><br>On Feb 1, 2017, at 3:47 PM, Matthew Johnson via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br><br></div><blockquote type="cite"><div><meta http-equiv="content-type" content="text/html; charset=utf-8"><div><br><br>Sent from my iPad</div><div><br>On Feb 1, 2017, at 5:11 PM, David Sweeris via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html charset=utf-8"><br class=""><div><blockquote type="cite" class=""><div class="">On Feb 1, 2017, at 3:01 PM, David Hart via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="content-type" content="text/html; charset=utf-8" class=""><div dir="auto" class=""><div class=""><br class=""></div><div class="">On 1 Feb 2017, at 22:54, Douglas Gregor <<a href="mailto:dgregor@apple.com" class="">dgregor@apple.com</a>> wrote:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jan 29, 2017, at 8:44 PM, Slava Pestov via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">This is a nice generalization of the existing protocol composition syntax. Implementation might get a little tricky — this touches a lot of things, such as inheritance clauses, constraints in generic signatures, and casts. It would require thorough testing.<div class=""><br class=""></div><div class="">There are also a few odd corner cases to sort out:</div><div class=""><br class=""></div><div class="">typealias T = SomeClass & SomeProtocol</div><div class=""><br class=""></div><div class="">class C : T { // should we allow this? probably yes</div><div class="">}</div><div class=""><br class=""></div><div class="">protocol P : T { // should we allow this? probably no</div><div class="">}</div></div></div></blockquote><div class=""><br class=""></div>IIRC, we already allow the latter where T is a typealias for SomeProtocol1 & SomeProtocol2. Why not allow it generally?</div></div></blockquote><div class=""><br class=""></div><div class="">Well what would it mean? A protocol can't inherit or conform to a class.</div></div></div></blockquote></div><br class=""><div class="">That anything which conforms to that protocol must subclass SomeClass?</div></div></blockquote><div><br></div><div>Yes, this is exactly what I would expect. I was calling it a supertype requirement earlier in the thread.</div><br><blockquote type="cite"><div><div class=""><br class=""></div><div class="">- Dave Sweeris</div></div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>swift-evolution mailing list</span><br><span><a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a></span><br><span><a href="https://lists.swift.org/mailman/listinfo/swift-evolution">https://lists.swift.org/mailman/listinfo/swift-evolution</a></span><br></div></blockquote></div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>swift-evolution mailing list</span><br><span><a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a></span><br><span><a href="https://lists.swift.org/mailman/listinfo/swift-evolution">https://lists.swift.org/mailman/listinfo/swift-evolution</a></span><br></div></blockquote></body></html>