anchor.diff:  
   
   %% @private
  +check_post_check(#parse{syntax = Syntax, ok = Ok} = Parse) ->
  +    case maps:get('__post_check', Syntax, none) of
  +        Fun when is_function(Fun, 1) ->
  +            case Fun(Ok) of
  +                ok ->
  +                    {ok, Parse};
  +                {error, {field, Key}} ->
  +                    {error, {syntax_error, path_key(Key, Parse)}};
  +                {error, Error} ->
  +                    {error, Error}
  +            end;
  +        _ ->
  +            {ok, Parse}
  +    end.
  +
  +
  +
  +%% @private
   to_existing_atom(Term) when is_atom(Term) ->
       {ok, Term};
   
  
positive.code:     list() |                    % First matching option is used
      syntax_fun() |
      '__defaults' |              % Defaults for this level #{atom() => term()}
      '__mandatory'.              % Mandatory fields for this level [atom()]
  
  -type key() :: atom().
  -type val() :: term().
  
negative.code:         {ok, Parse2} ->
              case check_mandatory(Parse2) of
                  ok ->
                      check_post_check(Parse2);
                  {error, Error} ->
                      {error, Error}
              end;
  