static S replaceOrDropCodeTokensUsingMap(S s, SS map) {
  ret join(replaceOrDropCodeTokensUsingMap(javaTok(s), map);
}

static LS replaceOrDropCodeTokensUsingMap(LS tok, SS map) {
  LS out = emptyList(tok);
  for i over tok: {
    if (odd(i)) out.add(tok.get(i));
    else {
      S val = lookupOrKeep(map, tok.get(i));
      if (nempty(val))
        out.add(val);
      else {
        out.add(ai_mergeWhitespace(last(out), tok.get(i+1)));
        i++;
      }
    }
  }
  ret out;
}

sS replaceOrDropCodeTokensUsingMap(SS map, S s) {
  ret replaceOrDropCodeTokensUsingMap(s, map);
}

Began life as a copy of #1014558