Type Level OneOf

OneOf.scala

trait OneOf[Obj, Items]

object OneOf extends LowPriorityOneOf{
  implicit def apply[Obj, Items](implicit oneOf: OneOf[Obj, Items]) = oneOf

  implicit def left[L, R, Obj <: L] = new OneOf[Obj, L | R]{}
}

protected trait LowPriorityOneOf extends LowPriorityOneOf1{
  implicit def right[L, R, Obj <: R] = new OneOf[Obj, L | R]{}
}

protected trait LowPriorityOneOf1{
  implicit def recur[L, R, Obj](implicit oneOf: OneOf[Obj, R]) = new OneOf[Obj, L | R]{}
}