static BasicLogicRule<S> ai_sharedWordsIntoDollarVars(BasicLogicRule<S> r) {
  LS words = antiFilter isDollarVar(sharedWords(r.lhs, r.rhs));
  SS map = ciMapWithUnusedCountingDollarVars(words, linesLL(r.lhs, r.rhs));
  ret mapBasicLogicRule(r, s -> replaceCodeTokensUsingMap(s, map));
}