Scala 2 existential typeclass pattern

exists.scala

object Main {
  def main(args: Array[String]) = {
    implicit val showInt = new Show[Int] {
      override def show(a: Int): String = a.toString
    }
​
    implicit val readInt = new Read[Int] {
      override def read(s: String): Int = s.toInt
    }
​
    val a = 5
​
    val e = Exists[Show](a)
​
    e match {
      case Exists(value, tc) => println(tc.show(value))
    }
  }
}
​
​
trait Show[A] {
  def show(a: A): String
}
​
trait Read[A] {
  def read(s: String): A
}
​
sealed trait Exists[C[_]] {
  type Value
  val value: Value
  val typeClassInstance: C[Value]
​
  final def use[R](f: C[Value] => Value => R): R = f(typeClassInstance)(value)
}
​
object Exists {
  private class ExistsConcrete[A, C[_]](override val value: A, override val typeClassInstance: C[A]) extends Exists[C] {
    override type Value = A
  }
​
​
  def apply[C[_]]: ApplyPartialApplicationHelper1[C] = new ApplyPartialApplicationHelper1()
​
  class ApplyPartialApplicationHelper1[C[_]] private[Exists]  {
    def apply[A](a: A)(implicit tc: C[A]): Exists[C] = new ExistsConcrete[A, C](a, tc)
  }
​
  def unapply[C[_]](e: Exists[C]): Some[(e.Value, C[e.Value])] = Some(e.value, e.typeClassInstance)
}