From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Michael Heerdegen <michael_heerdegen@web.de>
Cc: jixiuf <jixiuf@qq.com>, 45619@debbugs.gnu.org
Subject: bug#45619: 28.0.50; pcase-let on MacOS doesn't work
Date: Mon, 04 Jan 2021 21:06:27 -0500 [thread overview]
Message-ID: <jwv4kjw16nf.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <87wnws2w3o.fsf@web.de> (Michael Heerdegen's message of "Mon, 04 Jan 2021 23:08:59 +0100")
>> It's messier than that: the issue is that it doesn't bind variables
>> which aren't used lexically (this is needed to avoid spurious warnings
>> about unused vars when the var is used in on place but not in another).
> BTW, a similar issue (pitfall) I faced was that I sometimes expect that
> when a variable is already bound, already the first appearance of the
> symbol would be turned into an equality test.
Hmm... so-called "non-linear patterns". We should emit a warning when the
same var is used twice in a pattern, indeed, to avoid surprises.
We could also do as you describe but I'm not completely sure it's a good
idea (it begs questions about which equality test to use and when it
should be tested).
> I wonder if pcase variable bindings could be hygienic in the sense that
> they would use fresh symbols internally. That would maybe make the
> semantics clearer.
I don't know what you mean by that. Can you clarify?
Stefan
next prev parent reply other threads:[~2021-01-05 2:06 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-03 7:59 bug#45619: 28.0.50; pcase-let on MacOS doesn't work jixiuf
2021-01-04 12:44 ` Michael Heerdegen
2021-01-04 15:41 ` Drew Adams
2021-01-04 17:41 ` Stefan Monnier
2021-01-04 19:50 ` Michael Heerdegen
2021-01-04 20:37 ` Stefan Monnier
2021-01-04 22:08 ` Michael Heerdegen
2021-01-05 2:06 ` Stefan Monnier [this message]
2021-01-07 11:38 ` Michael Heerdegen
2021-01-07 15:19 ` Stefan Monnier
2021-01-08 20:05 ` Michael Heerdegen
2021-01-08 22:13 ` Stefan Monnier
2022-02-12 7:46 ` Lars Ingebrigtsen
2022-02-12 14:56 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-02-12 16:30 ` Lars Ingebrigtsen
2022-02-12 17:10 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-02-12 17:21 ` Lars Ingebrigtsen
2022-02-12 22:33 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
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