Replace Observer with a generic typealias?

[andersio]

Observers can now be represented using a generic typealias, since they carry no context other than the closure:

extension Signal {
    public typealias Observer<Value, Error> = (Event<Value, Error>) -> Void
}

Without the shorthands, it doesn't seem to hurt the legibility at call site.

observer.send(value: 1)
observer(.value(1))

observer.sendCompleted()
observer(.completed)

observer.sendInterrupted()
observer(.interrupted)

observer.send(error: Error())
observer(.failed(error))

The downside is impossible migration.

Related: Observer was introduced in ReactiveCocoa/ReactiveCocoa#2442 to replace the send* free functions and Event.Sink.