Add type level boolean to OneOf

OneOfProof.scala

trait OneOfProof[Obj, Types] {
  type Cond <: Bool
}

object OneOfProof extends OneOfProof1{
  implicit def left[Obj, R]: Aux[Obj, Obj | R, True] = new OneOfProof[Obj, Obj | R] { type Cond = True }
}

trait OneOfProof1 extends OneOfProof2{
  implicit def right[Obj, L]: Aux[Obj, L | Obj, True] = new OneOfProof[Obj, L | Obj] { type Cond = True }
}

trait OneOfProof2 extends OneOfProof3{
  implicit def recur[Obj, L, R](implicit proof: OneOfProof[Obj, R]): Aux[Obj, L | R, proof.Cond] =
    new OneOfProof[Obj, L | R] { type Cond = proof.Cond }
}

trait OneOfProof3{
  type Aux[O, T, C <: Bool] = OneOfProof[O, T]{ type Cond = C }

  implicit def nt[Obj, L, R](implicit has: Aux[Obj, L | R, True]): Aux[Obj, L | R, False] = ???

  implicit def fail[Obj, L, R]: Aux[Obj, L | R, False] = new OneOfProof[Obj, L | R] { type Cond = False }
}

package.scala

package object lala{
  type |[A, B] = (A, B)

  sealed trait Bool
  sealed trait True extends Bool
  sealed trait False extends Bool

  type OneOf[Obj, Types] = OneOfProof.Aux[Obj, Types, True]
  type NotOneOf[Obj, Types] = OneOfProof.Aux[Obj, Types, False]
}