expandedtypemismatch.scala

  trait AbstractAgent[S,A] {
    type Self = AbstractAgent[S,A]
    def learn(s: S): Self
  }

  trait GameDomain {
    type State
    type Action
    type Agent <: AbstractAgent[State, Action]
  }

  case class LearningSimulation[G<:GameDomain with Singleton]( agent: G#Agent,
                                                               state: G#State)
  {
    def step: LearningSimulation[G] = {
      def newAgent = agent.learn(state): G#Agent // type mismatch
      copy(agent = newAgent)
    }
  }