`any` cannot be used for reference type parameters like `some` can

[JessyCatterwaul]

The last line doesn't compile.

protocol Protocol { }
final class Class { }
actor Actor { }
func ƒ(_: some Class & Protocol, _: some Actor & Protocol) { }
func ƒ(_: some Class, _: some Actor) { }
func ƒ(_: any Class & Protocol, _: any Actor & Protocol) { }
func ƒ(_: any Class, _: any Actor) { }

I think it would be better if it wouldn't compile for some, either, but they should both behave similarly regardless of what that behavior is.

[AnthonyLatsis]

This is expected behavior per the proposal. A generic parameter constrained to a class is a fair use case and static type abstraction, unlike this kind of class existential, which is completely redundant in practice. I don’t think symmetry is a good enough reason to allow any syntax on bare classes without imposing semantic weight, but you are welcome to start a discussion on the forums.

cc @hborla