sclass MechListDependentCache<A> extends Cache<A> {
  // maker is now F1<S, A>
  S listName, lastListContents;
  
  *() {}
  *(S *listName, O *maker) {}
  
  A make() { ret (A) callF(maker, lastListContents); }
  
  A get() {
    if (hasLock(lock)) ret value; // Must be called from within maker
    {
      S listContents = mL_raw(listName);
      lock lock;
      if (!eqOrSame(listContents, lastListContents))
        clear();
      lastListContents = listContents;
    }
    ret super.get();
  }
}

Began life as a copy of #1011310