anchor.diff:          {return, return} -> ""
       end.
   
  -get_warning_opt(Opts) ->
  +get_warning_opt_from_perspective_of_return(Opts) -> get_warn_opt(Opts, return).
  +get_warning_opt_from_perspective_of_output(Opts) -> get_warn_opt(Opts, report).
  +
  +get_error_opt_from_perspective_of_return(Opts) -> get_err_opt(Opts, return).
  +get_error_opt_from_perspective_of_output(Opts) -> get_err_opt(Opts, report).
  +
  +get_warn_opt(Opts, WhatToReturnIfBothAreSet) ->
       case {member(return_warnings, Opts), member(report_warnings, Opts)} of
           {false, false} -> report; %% default
           {true,  false} -> return;
  -        {false,  true} -> report
  -    end.
  -
  -get_error_opt(Opts) ->
  +        {false,  true} -> report;
  +        {true,   true} -> WhatToReturnIfBothAreSet
  +    end.
  +
  +get_err_opt(Opts, WhatToReturnIfBothAreSet) ->
       case {member(return_errors, Opts), member(report_errors, Opts)} of
           {false, false} -> report; %% default
           {true,  false} -> return;
  -        {false,  true} -> report
  +        {false,  true} -> report;
  +        {true,   true} -> WhatToReturnIfBothAreSet
       end.
   
   member(Elem, List) ->
  
positive.code:         {return, report, erroneous_code}  -> {error, '_', []}
      end;
  compute_expected_return(Options, to_proto_defs, SrcQuality) ->
      WarnOpt = get_warning_opt(Options),
      ErrOpt = get_error_opt(Options),
      case {WarnOpt, ErrOpt, SrcQuality} of
          {report, report, clean_code}      -> {ok, non_empty_list};
          {report, report, warningful_code} -> {ok, non_empty_list};
  
negative.code:                        [return_errors],
                         [report_warnings, return_errors],
                         [return_warnings, report_errors],
                         [return_warnings, report_warnings],
                         [return_errors, report_errors],
                         [return_warnings, report_warnings]
                         ++ [return_errors, report_errors],
                         []
                        ],
          CompileTo  <- [to_binary, to_file, to_proto_defs],
  