state2.scala

object Counter {
  type CounterState = State[Int, Int]
}

trait Counter {
  import Counter._
  def inc: CounterState = State { s => (s + 1, s + 1) }
}

trait Service {
  self: Counter =>
  import Counter._

  var currentCount: Int = ???

  def foo: Int = {
    val s = inc.run(???)
    currentCount = s.value._1
    s.value._2
  }

}

trait Service2 {
  self: Counter =>
  import Counter._

  var currentCount: CounterState = ???

  def foo: Int = {
    val s = inc.run(???)
    currentCount = s.value._1
    s.value._2
  }

}