Why can't I cast `Woo<Any>` to `Woo<Int>` concrete type? But `Array<Any>` to `Array<Int>` is OK?

[anon9791410]

@CharlesS

Would members on any Woo that don't involve the associated type in their signatures be callable here? I'm thinking of things like count on Array that work the same regardless of what the array's element is.

Yes. That's how things work already, with protocols:

func ƒ(collection: any Collection) -> (Any?, Int) {
  (collection.first, collection.count)
}

func ƒ<Collection: Swift.Collection>(collection: Collection) -> (Collection.Element?, Int) {
  (collection.first, collection.count)
}

some and any would be useful with all generic types—just, unlike with protocols, specifying the "associated type" would not useful, because unlike some/any Protocol<T>, there's nothing else for that to mean, other than Type<T> itself.

There hasn't been a lot of discussion yet. You all should start clamoring for it.

[Pitch] Use “some” to express “some specialization of a generic type”

Proposal The some keyword neatly replaces simple cases of <T> where T: Protocol. That said, I think there is an opportunity for a bit of syntactic sugar to elevate the readability of generics. In particular, I think it would be nice if Generic<some A, some B> could also be written as some Generic where A and B are the protocol requirements of Generic's type parameters. Reason The most obvious benefit of this is preventing generic type nesting beyond the point where every possible specializati…