Scala HList strip suffix

StripSuffix.scala

import shapeless.{ ::, DepFn2, HList, HNil }
import scala.annotation.implicitNotFound

/**
 * Returns {Out = B} after stripping suffix {A} from {BA}
 * {{{
 *    val a: Int :: String :: HNil  1 :: "a" :: HNil
 *    val ba: Boolean :: String :: Int :: String :: HNil = true :: "b" :: 1 :: "a" :: HNil
 *    val b: Boolean :: String :: HNil = StripSuffix[Int :: String :: HNil, Boolean :: String :: Int :: String :: HNil](a, ba)
 * }}}
 */
@implicitNotFound("Cannot find suffix ${A} in ${BA}")
trait StripSuffix[A <: HList, BA <: HList] extends DepFn2[A, BA] {
  type Out <: HList
}

object StripSuffix {
  type Aux[A <: HList, BA <: HList, B <: HList] = StripSuffix[A, BA] {
    type Out = B
  }

  implicit def equalCase[BA <: HList]: Aux[BA, BA, HNil] = new StripSuffix[BA, BA] {
    type Out = HNil
    def apply(a: BA, ba: BA): Out = HNil
  }

  implicit def hlistCase[A <: HList, BH, BT <: HList, BtOut <: HList](
    implicit up: StripSuffix.Aux[A, BT, BtOut]
  ): StripSuffix.Aux[A, BH :: BT, BH :: BtOut] = new StripSuffix[A, BH :: BT] {
    type Out = BH :: BtOut
    def apply(a: A, ba: BH :: BT) =
      ba.head :: up.apply(a, ba.tail)
  }

  def apply[A <: HList, BA <: HList](
    implicit stripSuffix: StripSuffix[A, BA]
  ): StripSuffix.Aux[A, BA, stripSuffix.Out] = stripSuffix
}