@Override
  public void afterMerge(@NotNull DfaMemoryState other) {
    super.afterMerge(other);
    assert other instanceof TrackingDfaMemoryState;
    MemoryStateChange otherHistory = ((TrackingDfaMemoryState)other).myHistory;
    myHistory = myHistory == null ? otherHistory :
                otherHistory == null ? myHistory :
                myHistory.merge(otherHistory);
  }
@Override
  public void afterMerge(@NotNull DfaMemoryState other)