class MailBox {
  //class Message 
  type Message = AnyRef
}   
   
abstract class Actor {
  private val in = new MailBox

  def send(msg: in.Message) =  error("foo")

  def unstable: Actor = error("foo")

  def dubiousSend(msg: MailBox#Message) = 
    unstable.send(msg) // in.Message becomes unstable.Message, but that's ok since Message is a concrete type member
}      
