shapeless-path.scala

  def path[A, B <: AnyRef](name: String, value: A, parent: B): FieldType[(name.type, parent.type), A] =
    field[(name.type, parent.type)].apply[A](value)

  def emptyPath[A](value: A): FieldType[Nothing, A] = field[Nothing](value)

  trait Path[A] {
    type Out <: HList
    val value: Out
  }

  trait LowPriorityPath {
    type Aux[A, B] = Path[A] {
      type Out = B
    }

    implicit def nilPath[V]: Aux[FieldType[Nothing, V], HNil] = new Path[FieldType[Nothing, V]] {
      type Out = HNil
      val value = HNil
    }
  }

  object Path extends LowPriorityPath {
    implicit def consPath[A <: String, K, V <: AnyRef](
      implicit
      w:    Witness.Aux[A],
      rest: Path[V]
    ): Aux[FieldType[(w.T, K), V], A :: rest.Out] = new Path[FieldType[(w.T, K), V]] {
      type Out = w.T :: rest.Out
      val value = w.value :: rest.value
    }

    def apply[A <: AnyRef](a: A)(implicit p: Path[A]): p.Out = p.value
  }

  object Z

  object Y {
    def z = path("z", Z, this)
  }

  object X {
    def y = path("y", Y, this)
  }

  val x = emptyPath(X)
  val v = x.y.z
  val result = Path(v)
  result: Witness.`"z"`.T :: Witness.`"y"`.T :: HNil