Tagged types experiment

tagged.scala

bject Tag {

  type Tagged[T] = {
    type Tag = T
  }


  type @@[A, T] = A with Tagged[T]


  final class NewType[A](val underlying: A) extends AnyVal {

  }

//  final class Tagger[U] {
//    def apply[T](t: T): T @@ U = t.asInstanceOf[T @@ U]
//  }
//
//  def tag[U] = new Tagger[U]

  final implicit class RichAnyRef[A <: AnyRef](val underlying: A) extends AnyVal {
    def tag[T]: A @@ T = underlying.asInstanceOf[A @@ T]
  }

  final implicit class RichInt(val underlying: Int) extends AnyVal {
    def tag[T]: Int @@ T = underlying.asInstanceOf[Int @@ T]
  }

  def tag[T](i: Int): Int @@ T = i.asInstanceOf[Int @@ T]

  final class Foo
  final class Bar

  val f = 5.tag[Foo]
  val b = 6.tag[Bar]
  val a = tag[Foo](0)

  val x = 1 - f
  val y = f - b

  val fs: List[Int @@ Foo] = List(f)
  val bs: List[Int @@ Bar] = List(b)

}