Shapeless : Checking of the Type Constraints of Polymorphic Functions (lifted types)

shapeless_example.scala

// details: https://stackoverflow.com/questions/44159203/shapeless-checking-of-the-type-constraints-of-polymorphic-functions-lifted-ty
import shapeless._
import ops.hlist._
import ops.function._
import syntax.std.function._

object ShapelessExample {

  case class Place[A](a: A) extends AnyVal

  implicit class Ops[P <: Product, L <: HList, U <: HList, C <: HList](p: P)(
    implicit
      val g: Generic.Aux[P, L],
      val l: LiftAll.Aux[Unwrapped, L, U],
      val c: Comapped.Aux[L, Place, C]) {

    def ~|>[F, R](fn: F)(implicit fp: FnToProduct.Aux[F, C ⇒ R]) = {

      def fuckitZip(l1: HList, l2: HList): HList = (l1, l2) match {
        case (h1 :: t1, h2 :: t2) => (h1, h2) :: fuckitZip(t1, t2)
        case _ => HNil
      }

      def fuckitMap(l: HList, f: Any => Any): HList = l match {
        case HNil => HNil
        case h :: t => f(h) :: fuckitMap(t, f)
      }

      def f(a: Any): Any = a match {
        case (y: Any, x: Any) =>
          x.asInstanceOf[Unwrapped[Any] {type U = Any}].unwrap(y)
      }

      val zp = fuckitZip(g.to(p), l.instances)
      val uw = fuckitMap(zp, f _).asInstanceOf[C]
      fn.toProduct(uw)
    }
  }


  val p1 = Place(1)
  val p2 = Place(2)

  val res = (p1,p2, p2) ~|> ((x: Int, y: Int, z: Int) ⇒ x + y + z)
}