anchor.diff:          [] when Label == '$_els' ->
               {Var, sub_els};
           [] ->
  -            io:format("Labels = ~p~n", [Labels]),
               bad_spec({unresolved_label, Label, TagName});
           [#attr{} = S] ->
               {Var, S};
  
positive.code:                _ -> "attr"
             end,
      Clause1 = erl_syntax:clause(
                  [abstract(<<>>)],
                  none,
                  [if IsRequired ->
                           make_function_call(
  
negative.code:                              [erl_syntax:variable("_attrs")|
                                lists:flatmap(
                                  fun({_Var, #attr{}}) ->
                                          [erl_syntax:atom(undefined)];
                                     (_) ->
                                          []
                                  end, Calls)]),
  