Locking based on object equality rather than referential equality in Scala

EquivalenceLock.scala

/**
  * An util that provides synchronization using value equality rather than referential equality
  * It is guaranteed that if two objects are value-equal, their corresponding blocks are invoked mutually exclusively.
  * But the converse may not be true i.e. if two objects are not value-equal, they may be invoked exclusively too
  * Note: Typically, no need to create instances of this class. The default instance in the companion object can be safely reused
  *
  * @param size There is a 1/size probability that two invocations that could be invoked concurrently is invoked sequentially
  *
  * Example usage:
  *   import EquivalenceLock.{defaultInstance => lock}
  *   def run(person: Person) = lock(person) { .... }
  */
class EquivalenceLock(val size: Int) {
  private[this] val locks = IndexedSeq.fill(size)(new Object())
  def apply[A](lock: Any)(f: => A): A = locks(lock.hashCode().abs % size).synchronized(f)
}

object EquivalenceLock {
  implicit val defaultInstance = new EquivalenceLock(1 << 10)
}