anchor.diff:  
   -type parse_ret() :: {'ok', erl_parse_expr_list(), line()}
                      | {'eof', line()}
  -                   | {'error', erl_scan:error_info(), line()}.
  +                   | {'error', erl_scan:error_info(), line()}
  +                   | request_error().
   
   -spec parse_erl_exprs(prompt()) -> parse_ret().
   
  
positive.code: 
  -type parse_form_ret() :: {'ok', erl_parse_absform(), line()}
                          | {'eof', line()}
                          | {'error', erl_scan:error_info(), line()}.
  
  -spec parse_erl_form(prompt()) -> parse_form_ret().
  
  
negative.code: -type device() :: atom() | pid().
  -type prompt() :: atom() | string().
  
  -type error_description() :: term(). % Whatever the io-server sends.
  -type request_error() :: {'error',error_description()}.
  %% XXX: Some uses of line() in this file may need to read erl_scan:location()
  -type line()   :: pos_integer().
  
  