Cannot safely cast "Promise" to "Deferred"

[loretoparisi]

I get this error

Cannot safely cast "Promise" to "Deferred" did you mean to use as!?

in

for promise in promises {
                var p = (promise as? Deferred == nil) ? promise : (promise as Deferred).promise
                self.promises.append(p)
                p.statusObserver = observe
            }

So I can try a nullable like

 for promise in promises {
                var p = (promise as? Deferred == nil) ?
                    promise :
                    (promise as? Deferred).promise
                self.promises.append(p)
                p.statusObserver = observe
            }

        }

This time the compiler complains (but a warn) that

Nullable must be unwrapped