anchor.diff:  			SwpFileName = filename:rootname(FileName, ".erl") ++ ".erl.swp",  %% .erl.swp or .swp.erl?
   			case file:write_file(SwpFileName, list_to_binary(refac_prettypr:print_ast(FileFormat, AST))) of 
   			    ok -> {{FileName,NewFileName, false},SwpFileName};
  -			    _  -> error
  +			    {error,Reason} -> Msg = io_lib:format("Wrangler could not write to directory ~s: ~w \n",
  +								  [filename:dirname(FileName), Reason]),
  +					      throw({error, Msg})
   			end;			
   		    {{FileName,NewFileName, IsNew}, AST} ->
   			FileFormat = file_format(FileName),
   			SwpFileName = filename:rootname(FileName, ".erl") ++ ".erl.swp", 
   			case file:write_file(SwpFileName, list_to_binary(refac_prettypr:print_ast(FileFormat, AST))) of 
   			    ok -> {{FileName,NewFileName, IsNew},SwpFileName};
  -			    _  -> error
  +			    {error, Reason}  -> 
  +				Msg = io_lib:format("Wrangler could not write to directory ~s: ~w \n",
  +						    [filename:dirname(FileName), Reason]),
  +				throw({error, Msg})
   			end
  -		    end
  +		end
   	end,
       FilePairs = lists:map(F, Files),
       case lists:any(fun(R) -> R == error end, FilePairs) of 
  
positive.code: %% ============================================
  -module(refac_util).
  
  -export([ghead/2, glast/2, to_lower/1, to_upper/1, try_evaluation/1,
           is_var_name/1, is_fun_name/1, is_expr/1, is_pattern/1,
  	 is_exported/2, inscope_funs/1,
           once_tdTU/3, stop_tdTP/3, full_tdTP/3,full_buTP/3,
           pos_to_fun_name/2, pos_to_fun_def/2,pos_to_var_name/2,
           pos_to_expr/3, pos_to_expr_list/3, pos_to_expr_or_pat_list/3, pos_to_syntax_units/6, 
  	 pos_to_syntax_units/4, expr_to_fun/2,get_range/1,get_toks/1, concat_toks/1, tokenize/3,
           get_var_exports/1, get_env_vars/1, get_bound_vars/1, get_free_vars/1, 
           get_client_files/2, expand_files/2, get_modules_by_file/1,
           reset_attrs/1, update_ann/2,parse_annotate_file_1/5, parse_annotate_file/3,
           parse_annotate_file/4,write_refactored_files/1, write_refactored_files_for_preview/2,
           build_lib_side_effect_tab/1, build_local_side_effect_tab/2,
  	 build_scc_callgraph/1,build_callercallee_callgraph/1, has_side_effect/3,
           callback_funs/1,auto_imported_bifs/0, called_funs/2, file_format/1, rewrite/2,
  	 predefined_macros/0, default_incls/0]).
  
  -export([test_framework_used/1]).
  -export([analyze_free_vars/1, remove_duplicates/1]).
  
negative.code: 
  
  
  %%=================================================================
  %% @doc Return true if the abstract syntax tree represented by Node has side effect, 
  %%      otherwise return false. As to parameters, File represents filename of the
  