[swift-users] Workarounds for SR-6039?

[Marc Palmer]

Hi,

It’s hard to be 100% certain because of bugs.swift.org being down currently, but I believe I have hit this bug:

https://bugs.swift.org/browse/SR-6039 "A `protocol A: class` is not any `AnyObject`”

This is marked as a duplicate of a presumably very old issue judging by its low number:

https://bugs.swift.org/browse/SR-55 "non- at objc protocol existentials do not conform to their own protocol type"

So, I have a protocol:

public protocol ActionAuditorObserver: AnyObject {
    func actionAuditorInserted(entries: [ActionAuditEntry])
}

…where ActionAuditEntry is a struct.

Trying to use a generic collection of my own for these, of the form:

class ObserverSet<T: AnyObject> {
…
}

Using:

let observers = ObserverSet<ActionAuditorObserver>()

…results in "'ActionAuditorObserver' is not convertible to ‘AnyObject’”.

I think this is indeed SR-6039, which makes me really sad as it implies this is not going to be fixed imminently.

I am trying to write this as a pure-swift framework as so far have succeeded. If I add @objc to the protocol as a workaround for this, I then can no longer have the observer pass in an array of structs.

So then I have to change the struct to a class, and I’m pushed farther away from my goals :(

Is there anything I am missing, or a better way to workaround this?

I have to have the ObserverSet require AnyObject because it needs to do identity checking when removing them. Equatable does not make sense for observers. Losing the struct and forcing @objc feels like such a bitter pill for something so simple.

Thanks in advance
Marc