summonFrom.scala

import scala.compiletime.summonFrom

trait Show[A]:
  def show(a: A): String

given Show[String] with 
  def show(a: String): String = s"String: $a"

inline def show[A](a: A) = summonFrom:
  case show: Show[A] => show.show(a)
  case _ => s"Unknown type: $a"

@main def main =
  println(show(42))
  println(show("Scala 3"))