> On Jul 30, 2017, at 5:03 PM, Tino Heth <2...@gmx.de> wrote: > >> [Apologies if this is in Swift 4 already.] >> >> We can have generic parameters match a protocol. But I have an idea in my >> head that involves the type NOT conforming to a protocol. I don’t think we >> have a way currently to work with this. > Why do you want that? > When something conforms, you know that you can call the methods of the > protocol, but without conformance, you can't do anything that's not possible > using "is". > Also: > Don't forget retroactive conformance — you can never rely on non-conformance.
I forgot about that last part. But my idea still has merit, due to why I desired it in the first place. The “AnyObject” protocol is marked on all class types. All class types conform to it, and it’s illegal (as I understand it) to put on a type that isn’t already a class. I have been working on a “strong type-alias” proposal, and it has a similar protocol. And I came up with ideas that depend on a type NOT being a strong type-alias. That’s what prompted the post. Note that these protocols cannot be retroactively applied, so negation has merit. Since there’s a limited number of them, a better solution could be to add a “NeverAnObject” protocol that’s automatically slapped onto non-class types (and cannot be added onto class types). And like “AnyObject,” it can be a base protocol, but this time it forces the conforming protocol to not be for classes. — Daryle Walker Mac, Internet, and Video Game Junkie darylew AT mac DOT com _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
