// name -> (name, parsed map)
static Map<S, Pair<S, SS>> mechMapCI_cache = synchroMap();

please include function parseDoubleLeftArrowMapCI_tlft.

static SS mechMapCI(S listName) {
  Pair<S, SS> p = mechMapCI_cache.get(listName);
  S text = mechList_raw(listName);
  if (p != null && eq(p.a, text)) ret p.b;
  S parsing = first(mechList_opt(listName + " | Parsing"));
  SS map;
  if (parsing == null)
    map = parseDoubleArrowMapCI(tlft(text));
  else
    ifdef FancyMechParsing
      map = asCIMap((SS) callAndMake(parsing, text));
    endifdef
    ifndef FancyMechParsing
      map = asCIMap((SS) callMC(parsing, text));
    endifndef
  p = pair(text, map);
  mechMapCI_cache.put(listName, p);
  ret p.b;
}

Began life as a copy of #1014191