This warning can be suppressed using 'with-suppressed-warnings' with
the warning name 'suspicious'.
+---
+*** Warn about more ignored function return values.
+The compiler now warns when the return value from certain functions is
+ignored. Example:
+
+ (progn (nreverse my-list) my-list)
+
+will elicit a warning because it is usually pointless to call
+'nreverse' on a list without using the returned value. To silence the
+warning, make use of the value in some way, such as assigning it to a
+variable. You can also wrap the function call in '(ignore ...)'.
+
+This warning can be suppressed using 'with-suppressed-warnings' with
+the warning name 'ignored-return-value'.
+
+++
** New function 'file-user-uid'.
This function is like 'user-uid', but is aware of file name handlers,
;; so maybe we don't need to bother about it here?
(setq form (cons 'progn (cdr form)))
(setq handler #'byte-compile-progn))
- ((and (or sef (eq (car form) 'mapcar))
+ ((and (or sef
+ (memq (car form)
+ ;; FIXME: Use a function property (declaration)
+ ;; instead of this list.
+ '(
+ ;; Functions that are side-effect-free
+ ;; except for the behaviour of
+ ;; functions passed as argument.
+ mapcar mapcan mapconcat
+ cl-mapcar cl-mapcan cl-maplist cl-map cl-mapcon
+ cl-reduce
+ assoc assoc-default plist-get plist-member
+ cl-assoc cl-assoc-if cl-assoc-if-not
+ cl-rassoc cl-rassoc-if cl-rassoc-if-not
+ cl-member cl-member-if cl-member-if-not
+ cl-adjoin
+ cl-mismatch cl-search
+ cl-find cl-find-if cl-find-if-not
+ cl-position cl-position-if cl-position-if-not
+ cl-count cl-count-if cl-count-if-not
+ cl-remove cl-remove-if cl-remove-if-not
+ cl-member cl-member-if cl-member-if-not
+ cl-remove-duplicates
+ cl-subst cl-subst-if cl-subst-if-not
+ cl-substitute cl-substitute-if
+ cl-substitute-if-not
+ cl-sublis
+ cl-union cl-intersection
+ cl-set-difference cl-set-exclusive-or
+ cl-subsetp
+ cl-every cl-some cl-notevery cl-notany
+ cl-tree-equal
+
+ ;; Functions that mutate and return a list.
+ cl-delete-if cl-delete-if-not
+ ;; `delete-dups' and `delete-consecutive-dups'
+ ;; never delete the first element so it's
+ ;; safe to ignore their return value, but
+ ;; this isn't the case with
+ ;; `cl-delete-duplicates'.
+ cl-delete-duplicates
+ cl-nsubst cl-nsubst-if cl-nsubst-if-not
+ cl-nsubstitute cl-nsubstitute-if
+ cl-nsubstitute-if-not
+ cl-nunion cl-nintersection
+ cl-nset-difference cl-nset-exclusive-or
+ cl-nreconc cl-nsublis
+ cl-merge
+ ;; It's safe to ignore the value of `sort'
+ ;; and `nreverse' when used on arrays,
+ ;; but most calls pass lists.
+ nreverse
+ sort cl-sort cl-stable-sort
+
+ ;; Adding the following functions yields many
+ ;; positives; evaluate how many of them are
+ ;; false first.
+
+ ;;delq delete cl-delete
+ ;;nconc plist-put
+ )))
(byte-compile-warning-enabled-p
'ignored-return-value (car form)))
(byte-compile-warn-x