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bug#26486: 25.1.91; unused var warning from cconv.el can't be suppressed
From: |
Stefan Monnier |
Subject: |
bug#26486: 25.1.91; unused var warning from cconv.el can't be suppressed |
Date: |
Mon, 05 Jul 2021 11:29:40 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
Lars Ingebrigtsen [2021-07-05 17:17:06] wrote:
> Noam Postavsky <npostavs@users.sourceforge.net> writes:
>
>> This happens also without a macro.
>>
>> ;; -*- lexical-binding: t; byte-compile-warnings: nil -*-
>> (with-no-warnings (let (unused)))
>
> This currently gives a warning about both an unused variable and an
> empty let body.
>
> The following seemingly straightforward patch fixes both these things,
> I'd appreciate it if somebody had a look over it first, though. :-)
> (So Stefan M added to the CCs.)
[...]
> @@ -259,7 +259,8 @@ cconv--warn-unused-msg
> (not (intern-soft var))
> (eq ?_ (aref (symbol-name var) 0))
> ;; As a special exception, ignore "ignore".
> - (eq var 'ignored))
> + (eq var 'ignored)
> + (not (byte-compile-warning-enabled-p 'unbound var)))
> (let ((suggestions (help-uni-confusable-suggestions (symbol-name
> var))))
> (format "Unused lexical %s `%S'%s"
> varkind var
LGTM, thank you. This said, I suspect that it may fail to correctly
heed `with-suppressed-warnings`. More specifically, I think we may want
to add a "category" argument to `macroexp-warn-and-return` which is then
matched against `byte-compile-warnings` (either directly inside
`macroexp-warn-and-return` or within the subsequent handling of
`macroexp--funcall-if-compiled`).
> diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
> index 70999648d4..d97bc1073b 100644
> --- a/lisp/emacs-lisp/bytecomp.el
> +++ b/lisp/emacs-lisp/bytecomp.el
> @@ -325,6 +325,7 @@ byte-compile-warnings
> docstrings docstrings that are too wide (longer than 80 characters,
> or `fill-column', whichever is bigger)
> suspicious constructs that usually don't do what the coder wanted.
> + empty-body the body of a binding form is empty.
>
> If the list begins with `not', then the remaining elements specify warnings
> to
> suppress. For example, (not mapcar) will suppress warnings about mapcar."
> diff --git a/lisp/emacs-lisp/cconv.el b/lisp/emacs-lisp/cconv.el
> index f663710902..f1579cda8b 100644
> --- a/lisp/emacs-lisp/cconv.el
> +++ b/lisp/emacs-lisp/cconv.el
> diff --git a/lisp/emacs-lisp/macroexp.el b/lisp/emacs-lisp/macroexp.el
> index df864464b7..e9c2eb3fee 100644
> --- a/lisp/emacs-lisp/macroexp.el
> +++ b/lisp/emacs-lisp/macroexp.el
> @@ -319,14 +319,16 @@ macroexp--expand-all
> (`(,(and fun (or 'let 'let*)) . ,(or `(,bindings . ,body)
> pcase--dontcare))
> (macroexp--cons fun
> - (macroexp--cons (macroexp--all-clauses bindings 1)
> - (if (null body)
> - (macroexp-unprogn
> - (macroexp-warn-and-return
> - (format "Empty %s body" fun)
> - nil t))
> - (macroexp--all-forms body))
> - (cdr form))
> + (macroexp--cons
> + (macroexp--all-clauses bindings 1)
> + (if (null body)
> + (macroexp-unprogn
> + (macroexp-warn-and-return
> + (and (byte-compile-warning-enabled-p
> 'empty-body)
> + (format "Empty %s body" fun))
> + nil t))
> + (macroexp--all-forms body))
> + (cdr form))
> form))
> (`(,(and fun `(lambda . ,_)) . ,args)
> ;; Embedded lambda in function position.
We already discussed the use(ful|less)ness of this empty-body warning,
and I don't think it's useful enough to justify adding a new warning
category for it.
When `byte-compile-warnings` is nil, arguably `macroexp-warn-and-return`
should just silence all warnings.
Stefan