bug#69108: closed (false-positive warning "variable ‘_’ not left unused" in if-let* and if-let)

[GNU bug Tracking System]

Your message dated Sun, 25 Feb 2024 09:42:07 +0200
with message-id <86a5npxa5s.fsf@gnu.org>
and subject line Re: bug#69108: false-positive warning "variable ‘_’ not left 
unused" in if-let* and if-let
has caused the debbugs.gnu.org bug report #69108,
regarding false-positive warning "variable ‘_’ not left unused" in if-let* and 
if-let
to be marked as done.

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-- 
69108: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=69108
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> --- Begin Message ---
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>
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> Subject: 
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> false-positive warning "variable ‘_’ not left unused" in if-let* and if-let
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> Date: 
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> Wed, 14 Feb 2024 00:21:01 +0300
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> User-agent: 
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> Evolution 3.50.3 
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>
>
>
> I've been writing an answer for a question on emacs.stackexchange¹ and to avoid
> nested `if` and `let` clauses I used a `if-let*`, and result of one of the 
> checks I
> assigned to a `_` variable, because the variable would be left unused, it's 
> only the
> check being non-nil that mattered.
>
> But when byte-compiled that triggered a:
>
>     test.el:6:9: Warning: variable ‘_’ not left unused
>
> …which is untrue, because it is unused.
>
> The problem is present in both `if-let` and `if-let*`
>
> # Steps to reproduce
>
> 1. Create test.el with the following code:
>
>     ;;; -*- lexical-binding: t -*-
>     (if-let*
>         ((_ nil))
>         (print "then clause")
>       (print "else clause"))
>
> 2. M-x byte-compile test.el
>
> ## Expected
>
> It byte-compiles with no warnings
>
> ## Actual
>
> It compiles with a warning:
>
>     test.el:3:7: Warning: variable ‘_’ not left unused
>
> # Additional information
>
> Emacs version: commit d4d5830f8a0 built two weeks ago from master.
>
> 1: https://emacs.stackexchange.com/questions/80351/delete-prettify-symbol
>
>
>
> --- End Message ---
> --- Begin Message ---
>
>
>
> Subject: 
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> Re: bug#69108: false-positive warning "variable ‘_’ not left unused" in if-let* and if-let
>
>
>
>
> Date: 
>
> Sun, 25 Feb 2024 09:42:07 +0200
>
>
>
>
> > From: Michael Heerdegen <michael_heerdegen@web.de>
> > Cc: 69108@debbugs.gnu.org,  Hi-Angel@yandex.ru
> > Date: Sun, 25 Feb 2024 02:54:04 +0100
> > 
> > Eli Zaretskii <eliz@gnu.org> writes:
> > 
> > > > [...] repeating a test.  Is this what you prefer?
> > >
> > > Yes, I think so.  And you could perhaps avoid repetition of
> > > (cdr binding) by saving the result of (null (cdr binding)) in
> > > a local variable.
> > 
> > I went with a separate `cond' branch added instead, I think this is even
> > simpler.  Ok?
>
> Yes, thanks.
>
> > > > {My unsuccessful doc tweaks}
> > >
> > > [...] I'd prefer to separate it.
> > 
> > Done.  Feel free to tune it to your likes.  Or send me an "ok", then
> > I'll just commit this version.
>
> I installed them both, thanks.
>
> Closing the bug.
>
>
> --- End Message ---