bug#29842: 27.0; `dired-change-marks': args should not be optional

[Tino Calancha]

Drew Adams <drew.adams@oracle.com> writes:

> Furthermore, the code should perhaps not just call
> `ding' if you hit RET.  Instead of this:
>
>  (if (or (eq old ?\r) (eq new ?\r))
>      (ding)
>   ...)
>
> it should perhaps do something like this:
>
>  (unless (char-displayable-p old)
>    (error "Not a displayable character: `%c'" old))
>  (unless (char-displayable-p new)
>    (error "Not a displayable character: `%c'" new))
>
> The current code predates the existence of
> `char-displayable-p'.
The more information the better; just a ding force you to read the
source code to know what was wrong.
Maybe `user-error' instead of `error'?