// Note: This does have the values problem (complicated values can cause memory leaks)
sclass BetterThreadLocal<A> {
  Map<Thread, A> map = newWeakHashMap();
  
  bool isSet() { ret map.containsKey(currentThread()); }
  
  A get() {
    ret map.get(currentThread());
  }
  
  A get(Thread thread) {
    ret map.get(thread);
  }
  
  void set(A a) {
    mapPutOrRemove(map, currentThread(), a);
  }
}