// BREAKING CHANGE!
// Also NOTE: Iterators of these sync-wrapped collections
// after generally NOT thread-safe!
// TODO: change that?
static <A> Set<A> synchroLinkedHashSet() {
  ifdef UseOldLinkedHashSet
    ret synchronizedSet(new LinkedHashSet<A>);
  endifdef
  ifndef UseOldLinkedHashSet
  ret synchronizedSet(new CompactLinkedHashSet);
  endifndef
}