How to use Changeset in protocols?

[pepasflo]

I can't figure out how to make the compiler happy when trying to express something like this:

public protocol ChangesetApplying: class {
    associatedtype T
    func apply(changeset: Changeset<T>)
}

The above will complain that Type 'Self.T' does not conform to protocol 'Collection'.

Changing it to associatedtype T: Collection yields a different error: Type 'Self.T.Iterator.Element' does not conform to protocol 'Equatable'.

Changing it to associatedtype T: Collection where T.Iterator.Element: Equatable, T.IndexDistance == Int yields the error 'where' clause cannot be attached to an associated type declaration, which appears to be the subject of SE-0142.

Any ideas?

[ZevEisenberg]

SE-0142 is implemented for Swift 4. Does this problem still exist in Swift 4?

[pepasflo]

Thanks for poking this ticket! I don't have Swift 4 installed yet, but I can check back in when I do. In the mean time, if someone else can confirm, that would be great!