(currentState: StringAdd).self
(currentState: StringFormat).self
(currentState: ArrowAssoc[CurrentState[S]]).x
(Since version 2.10.0) Use leftOfArrow instead
(currentState: Ensuring[CurrentState[S]]).x
(Since version 2.10.0) Use resultOfEnsuring instead
Message type which is sent directly to the subscribed actor in akka.actor.FSM.SubscribeTransitionCallBack before sending any akka.actor.FSM.Transition messages.