Called on match `//`
function consume_sl_comment (proc_stack) {
  let comment = "//";
  proc_stack.tSkip(2);
  let done = false;

  while (!proc_stack.tAtEnd() && !done) {
    let peek = proc_stack.tPeek();
    if (peek == "\r" || peek == "\n") {
      done = true;
    } else {
      comment += proc_stack.tAccept();
    }
  }

  return comment;
}