or and refute

refute.scala

trait Refute[A]

object Refute {
  implicit def ambiguous1[A](implicit ev: A): Refute[A] = new Refute[A] {}
  implicit def ambiguous2[A](implicit ev: A): Refute[A] = new Refute[A] {}
  implicit def refute[A]: Refute[A] = new Refute[A] {}
}

object TestRefute {
  trait Foo
  implicitly[Refute[Foo]]
}


trait Or[A, B] 

object Or {
  implicit def aAndB[A, B](implicit ev0: A, ev1: B): Or[A, B] = new Or[A, B] {}
  implicit def aNotB[A, B](implicit ev0: A, ev1: Refute[B]): Or[A, B] = new Or[A, B] {}
  implicit def bNotA[A, B](implicit ev0: B, ev1: Refute[A]): Or[A, B] = new Or[A, B] {}
}

object TestOr {
  trait Foo
  trait Bar

  object BothPresent {
    implicit val foo: Foo = new Foo {}
    implicit val bar: Bar = new Bar {}
    implicitly[Or[Foo, Bar]]
  }

  object NoFoo {
    implicit val bar: Bar = new Bar {}
    implicitly[Or[Foo, Bar]]
  }

  object NoBar {
    implicit val foo: Foo = new Foo {}
    implicitly[Or[Foo, Bar]]
  }
}