Trait based interning of case classes

Interning.scala

import scala.collection.mutable

sealed trait InterningProvider[K, V] {
  private[this] val cache =
    mutable.WeakHashMap[K, V]()

  protected def intern(args: (K))(builder: => V): V =
    cache.getOrElseUpdate(args, builder)
}

abstract class Internable1[A, Z](f: (A) => Z) extends InterningProvider[(A), Z] {
  def apply(a: A): Z =
    intern(a)(f(a))
}

abstract class Internable2[A, B, Z](f: (A, B) => Z) extends InterningProvider[(A, B), Z] {
  def apply(a: A, b: B): Z =
    intern(a, b)(f(a,b))
}


// Example

final case class CaseClassWithOneElementInterned(s: String)

object CaseClassWithOneElementInterned
      extends Internable1(new CaseClassWithOneElementInterned(_))