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

static L<S> replaceCodeTokensUsingMap(L<S> tok, SS map) {
  new L<S> out;
  for i over l: {
    S t = l.get(i);
    out.add(odd(i) ? lookupOrKeep(map, t) : t);
  }
  ret out;
}