Using SF-0011 with protocols

Using Swift
1

Because conformance to AnyObject is not the same as subtyping of any AnyObject, SF-0011 does not allow to use existentials of AnyObject-constrained protocols as Subject, unless they are marked as @objc.

protocol MySubject: AnyObject {
}

struct MyMessage: NotificationCenter.AsyncMessage {
    typealias Subject = any MySubject
}

class C: MySubject {
    private func notify() {
        // error: No exact matches in call to instance method 'post'
        NotificationCenter.default.post(MyMessage(), subject: self)
    }
}