>>    (defun next-error-quit-window ()
>>      (when (and (eq current-prefix-arg 0)
>>                 (not (eq next-error-last-buffer (current-buffer))))
>>        (let ((window (get-buffer-window next-error-last-buffer)))
>>          (when (window-live-p window)
>>            (with-selected-window window
>>              (quit-restore-window window))))))
>>    (add-hook 'next-error-hook 'next-error-quit-window)
>
> Since next-error-hook is a defcustom, perhaps we can/should include this
> function as one of the advertised values in :type?
>
> Even if we keep the list nil by default.

I completely forgot that we have 'next-error-found-function',
so implemented it with 'next-error-hook'.  I don't remember
why we have both.

Anyway, here is a patch with corrections from Martin: