anchor.diff:                              throw(Error)
                       end;
                   false ->
  -                    custom_tags_clauses_ast1(CustomTags, [Tag | ExcludeTags],
  -					     ClauseAcc, InfoAcc, Context, TreeWalker)
  +                    case call_extension(Context, custom_tag_ast, [Tag, Context, TreeWalker]) of
  +                        undefined ->
  +                            custom_tags_clauses_ast1(
  +                              CustomTags, [Tag | ExcludeTags],
  +                              ClauseAcc, InfoAcc, Context, TreeWalker);
  +                        {{Ast, Info}, TW} ->
  +                            Clause = erl_syntax:clause(
  +                                       [erl_syntax:atom(Tag), erl_syntax:variable("_Variables"), erl_syntax:variable("RenderOptions")],
  +                                       none, options_match_ast(Context, TW) ++ [Ast]),
  +                            custom_tags_clauses_ast1(
  +                             CustomTags, [Tag | ExcludeTags],
  +                             [Clause|ClauseAcc], merge_info(Info, InfoAcc),
  +                             Context, TW)
  +                    end
               end
       end.
   
  
positive.code: custom_tags_clauses_ast(CustomTags, Context, TreeWalker) ->
      custom_tags_clauses_ast1(CustomTags, [], [], #ast_info{}, Context, TreeWalker).
  
  custom_tags_clauses_ast1([], _ExcludeTags, ClauseAcc, InfoAcc, _Context, TreeWalker) ->
      {{lists:reverse(
          [erl_syntax:clause(
             [erl_syntax:variable("_TagName"), erl_syntax:underscore(), erl_syntax:underscore()], 
             none, 
             [erl_syntax:list([])])
           |ClauseAcc]),
        InfoAcc}, 
       TreeWalker};
  custom_tags_clauses_ast1([Tag|CustomTags], ExcludeTags, ClauseAcc, InfoAcc, Context, TreeWalker) ->
      case lists:member(Tag, ExcludeTags) of
          true ->
  
negative.code: %% Custom tags
  %%-------------------------------------------------------------------
  
  tag_ast(Name, Args, Context, TreeWalker) ->
      {{InterpretedArgs, AstInfo1}, TreeWalker1} = lists:foldr(fun
  								 ({{identifier, _, Key}, {trans, StringLiteral}}, {{ArgsAcc, AstInfoAcc}, TreeWalkerAcc}) ->
  