StackOverflow at compile time, Attempt to add OrElse to Poly

OrElse.scala

//This is all I'm adding...
object PolyDefns extends Cases{
  //stuff
  //.
  //.
  //.
  //my stuff

  class OrElse[F, G](f: F, g: G) extends Poly

  object OrElse extends LowPriorityOrElseImplicits {
    implicit def orElseCase[C, F <: Poly, G, L <: HList](implicit unpack: Unpack2[C, OrElse, F, G], ev: Case[F, L]): Case.Aux[C, L, ev.Result] = 
      new Case[C, L]{
        type Result = ev.Result
        val value = ev.value
      }
  }

  trait LowPriorityOrElseImplicits {
    implicit def orElseCase2[C, F, G <: Poly, L <: HList](implicit unpack: Unpack2[C, OrElse, F, G], ev: Case[G, L]): Case.Aux[C, L, ev.Result] = 
      new Case[C, L]{
        type Result = ev.Result
        val value = ev.value
      }
  }
}

//with declaration within Poly as
  def orElse(f: Poly) = new OrElse[this.type, f.type](this, f)

PolyTest.scala

//Within the unit tests

object one extends Poly3{
    implicit val iii = at[Int, Int, Int]{ 
      case (x, y, z) => x+y+z
    }
    implicit val iid = at[Int, Int, Double]{
      case (x, y, z) => 1.0
    }
  }
  object two extends Poly3{
    implicit val iid = at[Int, Int, Double]{
      case (x, y, z) => 2.0
    }
    implicit val idd = at[Int, Double, Double]{
      case (x, y, z) => 2.0
    }
  }

  @Test
  def testOrElse{
    { //Test with similar arity
      val gen = one orElse two

      assertTypedEquals[Int](gen(1, 1, 1), 3)
      assertTypedEquals[Double](gen(1, 1, 1.0), 1.0)
      assertTypedEquals[Double](gen(1, 1.0, 1.0), 2.0)
    }

    { //Test with different arity
      val gen = bidi orElse one

      assertTypedEquals[Int](gen("1"), 1)
      assertTypedEquals[Int](gen(1, 1, 1), 3)
    }
  }