Opaque Sealed Hierarchy

Root.scala

// Tired of subtyping and `extends Product with Serializable`?
// It is impossible to instantiate a concrete subtype of `Root`
// It preserves pattern matching exhaustiveness check

sealed abstract class Root
object Root {
  private final case class LeafInt(i: Int) extends Root
  object LeafInt { def apply(i: Int): Root = new LeafInt(i) }
  private final case class LeafString(s: String) extends Root
  object LeafString { def apply(s: String): Root = new LeafString(s) }
}