svoid tok_script_settable(LS tok) {
  int i;
  while ((i = jfind(tok, "settable <id> :")) >= 0) {
    S id = tok.get(i+2);
    int iType = i+6;
    S type = tok_script_scanType(tok, i+6);
    S getter = "def !synthetic " + id + ": " + type + " { this !_getField_ " + id + "}";
    S setter = "def !synthetic " + id + " " + id + ": " + type + " { this " + id + " <- " + id + "; this }";
    replaceToken_reTok(tok, i, joinWithSpace(getter, setter));
  }
}

Began life as a copy of #1036295