Deriving a nice Show in scala 3

Show.scala

import scala.deriving.*
import scala.compiletime.*

trait Show[T]:
  extension (t: T) def show: String

given Show[String] = s => s
given Show[Int] = _.toString

object Show:

  private inline def instances[T <: Tuple]: List[Show[Any]] =
    summonAll[Tuple.Map[T, Show]].toList.asInstanceOf[List[Show[Any]]]

  private inline def deriveAll[T <: Tuple]: Tuple = inline erasedValue[T] match {
    case _: EmptyTuple => EmptyTuple
    case _: (h *: t)   =>
      summonFrom { case given Mirror.Of[`h`] =>
        derived[h]
      } *: deriveAll[t]
  }

  inline def derived[T](
    using m: Mirror.Of[T]
  ): Show[T] = new Show[T]:

    extension (t: T)

      def show: String =
        inline m match {
          case p: Mirror.ProductOf[T] =>
            val label = summonInline[ValueOf[m.MirroredLabel]].value
            val fields = t.asInstanceOf[Product].productElementNames.toList
            val values = t.asInstanceOf[Product].productIterator.toList

            val paramString =
              if (fields.nonEmpty)(fields
                .zip(values)
                .zip(instances[p.MirroredElemTypes]))
                .map { case ((name, value), show) =>
                  s"$name = ${show.show(value)}"
                }
                .mkString("(", ", ", ")")
              else ""

            s"""$label$paramString"""

          case s: Mirror.SumOf[T] =>
            deriveAll[s.MirroredElemTypes].toList.asInstanceOf[List[Show[Any]]](s.ordinal(t)).show(t)
        }

enum Permission derives Show:
  case View
  case Edit
  case Both(p: Permission, p2: Permission)

import Show.given

@main def run =
  println((Permission.Both(Permission.View, Permission.Edit): Permission).show)