OneWayImplicits.scala

object OneWayImplicits {
  //outside implicits visible, but T is not visible inside
  case class Outwards[T](value: T) extends AnyVal

  //outside implicits invisible, T is visible inside
  case class Inwards[T](value: T) extends AnyVal

  implicit def outwardsFromT[T](implicit t: T): Outwards[T] = Outwards(t)
  implicit def tFromInwards[T](implicit inw: Inwards[T]): T = inw.value

  sealed trait X

  def usesOutwards()(implicit ow: Outwards[X]) = {
    //X is not implicitly visible here
    val x: X = ow.value
  }

  //doesn't get X from implicit scope
  def usesInwards(implicit iw: Inwards[X]) = {
    //but X is implicitly visible here
    ???
  }

  def composability(implicit x: Inwards[X]) = {
    usesOutwards() //gets `Outwards(x.value)`
  }
}