code: function maybe_name_with_default() {
    skip_horiz_white();
    if (look(/\[/)) {
      match(/\[/);
      maybe_ident_chain("name");
      skip_horiz_white();
      if (look(/=/)) {
        match(/=/);
        skip_horiz_white();
        current_tag["default"] = default_value();
      }
      skip_horiz_white();
      match(/\]/);
      current_tag["optional"] = true;
    }
    else {
      maybe_ident_chain("name");
    }
  }
docs: matches: <ident-chain> | "[" <ident-chain> [ "=" <default-value> ] "]"