From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org> Newsgroups: gmane.emacs.bugs Subject: bug#45619: 28.0.50; pcase-let on MacOS doesn't work Date: Sat, 12 Feb 2022 17:33:57 -0500 Message-ID: <jwvfsonn2gj.fsf-monnier+emacs@gnu.org> References: <tencent_420EB82A750AC42DCD81ECB23589C171FE07@qq.com> <877dos50su.fsf@web.de> <87k0e04jet.fsf@gnus.org> <jwvr188ywem.fsf-monnier+emacs@gnu.org> <87iltk11z5.fsf@gnus.org> <jwvv8xkovwb.fsf-monnier+emacs@gnu.org> <87ee480zms.fsf@gnus.org> Reply-To: Stefan Monnier <monnier@iro.umontreal.ca> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="3018"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) Cc: Michael Heerdegen <michael_heerdegen@web.de>, jixiuf <jixiuf@qq.com>, 45619@debbugs.gnu.org To: Lars Ingebrigtsen <larsi@gnus.org> Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Sat Feb 12 23:35:23 2022 Return-path: <bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org> Envelope-to: geb-bug-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from <bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org>) id 1nJ0zD-0000bi-88 for geb-bug-gnu-emacs@m.gmane-mx.org; 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Sat, 12 Feb 2022 17:33:58 -0500 (EST) In-Reply-To: <87ee480zms.fsf@gnus.org> (Lars Ingebrigtsen's message of "Sat, 12 Feb 2022 18:21:31 +0100") X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs.gnu.org> List-Unsubscribe: <https://lists.gnu.org/mailman/options/bug-gnu-emacs>, <mailto:bug-gnu-emacs-request@gnu.org?subject=unsubscribe> List-Archive: <https://lists.gnu.org/archive/html/bug-gnu-emacs> List-Post: <mailto:bug-gnu-emacs@gnu.org> List-Help: <mailto:bug-gnu-emacs-request@gnu.org?subject=help> List-Subscribe: <https://lists.gnu.org/mailman/listinfo/bug-gnu-emacs>, <mailto:bug-gnu-emacs-request@gnu.org?subject=subscribe> Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" <bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org> Xref: news.gmane.io gmane.emacs.bugs:226753 Archived-At: <http://permalink.gmane.org/gmane.emacs.bugs/226753> Lars Ingebrigtsen [2022-02-12 18:21:31] wrote: > Stefan Monnier <monnier@iro.umontreal.ca> writes: >> I don't think a single example can represent all cases. Try: >> >> (defun zot () >> (pcase-let (((or `(,foo) foo) '(2))) >> (progn (bar)))) > > Hm, yes. > >>>> I still think pcase should emit a warning when asked to bind >>>> a dynamically scoped variable. >>> If pcase-let currently does work fine for dynamic variables then it's >>> likely that people are depending on it, and it's too late to change... >> >> I don't mean to change the generated code, but to discourage such uses >> since they may break when the code is modified in apparently-minor ways. >> Hence a warning. > > Byte-compiling this does yield a warning in Emacs 29: > > pcase.el:6:28: Warning: Lexical argument shadows the dynamic variable foo Two problems with this: - The warning talks about the generated code rather than the source code, so it's hard for the user to understand what's going on (there's no *argument* by that name in their code). - The warning only shows up when the problem actually bites, whereas we should warn about all uses of dynamically scoped vars, since they all *may* bite at some point. - You only get the warning if you byte-compile the code. Stefan "off-by-one 4ever (in short, 5ever)"