anchor.diff:                       [erl_syntax:variable("_name"),
                         erl_syntax:variable("_xmlns")])],
                     none,
  -                  [make_function_call(
  -                     erlang, error,
  -                     [erl_syntax:tuple(
  -                        [erl_syntax:atom("unknown_tag"),
  -                         erl_syntax:variable("_name"),
  -                         erl_syntax:variable("_xmlns")])])]),
  +                  [make_erlang_error(
  +                     ModName,
  +                     erl_syntax:tuple(
  +                       [erl_syntax:atom("unknown_tag"),
  +                        erl_syntax:variable("_name"),
  +                        erl_syntax:variable("_xmlns")]))]),
       [make_function(
          "decode",
          [erl_syntax:match_expr(
  
positive.code:                 end, Elem#elem.refs)
        end, TaggedElems),
      G.
  
  %% make_type_spec(RefTag, {_, TypesDict, RecDict}) ->
  %%     ResType = dict:fetch(RefTag, TypesDict),
  
negative.code:     Arity = length(Args) + 1,
      case erlang:function_exported(?MODULE, Fun, Arity) of
          true ->
              {Fun, Args};
          false ->
              case lists:member({Fun, Arity}, KnownFunctions) of
                  true ->
  