static LPair<S, Pair<Int>> mruCachesWithStats() {
  ret mruCachesWithStats(mc());
}

static LPair<S, Pair<Int>> mruCachesWithStats(O mc) {
  new LPair<S, Pair<Int>> out;
  for (Pair<S, Map> p : allMapCacheVars(mc)) {
    Int max = maxSizeOfMRUCache(p.b);
    if (max != null)
      out.add(pair(p.a, pair(l(p.b), max)));
  }
  ret out;
}

Began life as a copy of #1021545