+ (signal 'file-supersession (cdr data)))
+ (text-read-only
+ ;; This signal may come either from `delete-active-region' or
+ ;; `self-insert-command' (when `overwrite-mode' is non-nil).
+ ;; To avoid clearing out `pre-command-hook' we handle this case
+ ;; by issuing a simple message. Note, however, that we do not
+ ;; handle all related problems: When read-only text ends before
+ ;; the end of the region, the latter is not deleted but any
+ ;; subsequent insertion will succeed. We could avoid this case
+ ;; by doing a (setq this-command 'ignore) here. This would,
+ ;; however, still not handle the case where read-only text ends
+ ;; precisely where the region starts: In that case the deletion
+ ;; would succeed but the subsequent insertion would fail with a
+ ;; text-read-only error. To handle that case we would have to
+ ;; investigate text properties at both ends of the region and
+ ;; skip the deletion when inserting text is forbidden there.
+ (message "Text is read-only") (ding))))))