if (lock == null) throw new IllegalMonitorStateException(); else
if (lock == null) { VM_Lock.raiseIllegalMonitorStateException("lock nursery: unlock", o); } else {
  public static void unlock (Object o) {    VM_Lock lock = nursery.findOrInsert(o, false);    if (lock == null)       throw new IllegalMonitorStateException();    else      lock.unlockHeavy(o);  }