type | [+A, +B] = Union.Type[A, B]
object Union {
  trait Tag extends Any
  type Base
  type Type[+A, +B] <: Base with Tag

  implicit def first[A]: A <:< Type[A, Nothing] =
    implicitly[A <:< A].asInstanceOf[A <:< Type[A, Nothing]]
  implicit def second[B]: B <:< Type[Nothing, B] =
    implicitly[B <:< B].asInstanceOf[B <:< Type[Nothing, B]]
}

object A
object B
object C

type X = A.type | B.type | C.type
type Y = A.type with B.type with C.type
implicitly[Y <:< X]