Trying to understand this...

matchtype.scala

trait POf2[Bi[_, _]] {
  def unapply[A, B](x: Bi[A, B]): Option[(A, B)]
}
implicit val TuplePOf2: POf2[Tuple2] = new POf2[Tuple2] {
  def unapply[A, B](x: (A, B)) = Some(x)
}
(1, 4) match { case TuplePOf2(a, b) => a + b }