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Better sort ignored-return-value warning

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* lisp/emacs-lisp/bytecomp.el (byte-compile-form)
(bytecomp--actually-important-return-value-p):
Special handling of `sort` that takes into account that it may return
an important value depending on the :in-place keyword argument.
This commit is contained in:
Mattias Engdegård 2024-03-24 18:18:41 +01:00
parent cbd862865f
commit b20866c4b3
1 changed files with 14 additions and 2 deletions
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16
lisp/emacs-lisp/bytecomp.el
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@ -3445,6 +3445,7 @@ lambda-expression."
((and (or sef (function-get (car form) 'important-return-value))
;; Don't warn for arguments to `ignore'.
(not (eq byte-compile--for-effect 'for-effect-no-warn))
(bytecomp--actually-important-return-value-p form)
(byte-compile-warning-enabled-p
'ignored-return-value (car form)))
(byte-compile-warn-x
@ -3471,6 +3472,15 @@ lambda-expression."
(if byte-compile--for-effect
(byte-compile-discard)))))
(defun bytecomp--actually-important-return-value-p (form)
"Whether FORM is really a call with a return value that should not go unused.
This assumes the function has the `important-return-value' property."
(cond ((eq (car form) 'sort)
;; For `sort', we only care about non-destructive uses.
(and (zerop (% (length form) 2)) ; new-style call
(not (plist-get (cddr form) :in-place))))
(t t)))
(let ((important-return-value-fns
'(
;; These functions are side-effect-free except for the
@ -3478,9 +3488,11 @@ lambda-expression."
mapcar mapcan mapconcat
assoc plist-get plist-member
;; It's safe to ignore the value of `sort' and `nreverse'
;; It's safe to ignore the value of `nreverse'
;; when used on arrays, but most calls pass lists.
nreverse sort
nreverse
sort ; special handling (non-destructive calls only)
match-data