sS compareMapsVerbose(Map a, Map b) {
  ret hijackPrint(r {
    if (a.size() != b.size()) ret with print("Size of map differs");
    for (O key, O value : (Map<O>) a) {
      if (!b.containsKey(key))
        print(key + " not found in map 2");
      else {
        O value2 = b.get(key);
        if (!eq(value, value2))
          print("values for key " + key + " differ");
        else
          print("values for key " + key + " ok");
      }
    }
  });
}