Implement HList reverse

hlistreverse.scala

import shapeless._

object console extends App {

  trait Reverse[T <: HList] {
    type Out <: HList
    def reverse(t: T): Out
  } 

  object Reverse {

    implicit def r[L <: HList, A <: HNil, Out0 <: HNil](implicit rtr: ReverseTR[L, A, Out0]): Reverse[L] = new Reverse[L] {
      type Out = Out0
      def reverse(l: L): Out = rtr.reverse(l, HNil.asInstanceOf[A])
    }

    trait ReverseTR[L <: HList, A <: HList, Out <: HList] {
      def reverse(l: L, a: A): Out
    } 

    object ReverseTR {

      implicit def rtrnil[A <: HList]: ReverseTR[HNil, A, A] = new ReverseTR[HNil, A, A] {
        def reverse(l: HNil, a: A): A = a 
      }

      implicit def rtrcons[H, T <: HList, A <: HList, Out <: HList]
        (implicit rtr: Lazy[ReverseTR[T, H :: A, Out]]): ReverseTR[H :: T, A, Out] = 
        new ReverseTR[H :: T, A, Out] {
          def reverse(l: H :: T, a: A): Out = rtr.value.reverse(l.tail, l.head :: a)
        }
    }
  }

  implicit class PrintOps[T <: HList](t: T) {
    def reverse(implicit r: Reverse[T]): r.Out = r.reverse(t)
  }
}