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