anchor.diff:  file(File, Opts) ->
       case parse_file(File, Opts) of
           {ok, Defs} ->
  +            possibly_probe_defs(Defs, Opts),
               Ext = filename:extension(File),
               Mod = list_to_atom(filename:basename(File, Ext)),
               Erl = change_ext(File, ".erl"),
               Hrl = change_ext(File, ".hrl"),
  -            file:write_file(Erl, format_erl(Mod, Defs, Opts)),
  -            file:write_file(Hrl, format_hrl(Mod, Defs, Opts));
  +            file_write_file(Erl, format_erl(Mod, Defs, Opts), Opts),
  +            file_write_file(Hrl, format_hrl(Mod, Defs, Opts), Opts);
           {error, _Reason} = Error ->
               Error
       end.
  
positive.code: 
  f(F)   -> f(F,[]).
  f(F,A) -> io_lib:format(F,A).
  
negative.code: parse_file_and_imports(FName, AlreadyImported, Opts) ->
      case locate_import(FName, Opts) of
          {ok, FName2} ->
              {ok,B} = file_read_file(FName2, Opts),
              %% Add to AlreadyImported to prevent trying to import it again: in
              %% case we get an error we don't want to try to reprocess it later
              %% (in case it is multiply imported) and get the error again.
  