[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
bug#31641: 26.1; iter-do variable not left unused warning
From: |
Lars Ingebrigtsen |
Subject: |
bug#31641: 26.1; iter-do variable not left unused warning |
Date: |
Thu, 04 Feb 2021 11:05:24 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
Noam Postavsky <npostavs@gmail.com> writes:
>> When byte-compiling an iter-do form with a variable intended to be
>> left unused, the compiler emits a false warning:
>>
>> ;;; -*- lexical-binding: t; -*-
>> (require 'generator)
>> (iter-do (_ i))
>> ;; -> "Warning: variable ‘_’ not left unused"
>
> Looking at the expansion, I guess the setf should be dropped if the
> variable name starts with _.
>
> (let (_
> #3=#:iter-do-result11
> (#1=#:iter-do-iterator-done8 nil)
> (#2=#:iter-do-iterator10 i))
> (while (not #1#)
> (condition-case #4=#:iter-do-condition9
> (setf _ (iter-next #2#))
> (iter-end-of-sequence
> (setf #3# (cdr #4#))
> (setf #1# t)))
> (unless #1#))
> #3#)
The following patch does this, but I'm not sure whether this is correct
or not -- in other cases, the _ convention just removes the warning, but
doesn't change the semantics.
I wondered whether we could just suppress this warning like this:
,(if (string-match-p "\\`_" (symbol-name var))
`(with-suppressed-warnings ((not-unused ,var))
(setf ,var (iter-next ,it-symbol)))
`(setf ,var (iter-next ,it-symbol)))
But no, cconv--analyze-use is called too early, and would have to be
taught about `with-suppressed-warnings'... which, looking at the code,
isn't immediately obvious how to do.
So does anybody have any ideas here?
diff --git a/lisp/emacs-lisp/generator.el b/lisp/emacs-lisp/generator.el
index 9eb6d95964..0b644cc72c 100644
--- a/lisp/emacs-lisp/generator.el
+++ b/lisp/emacs-lisp/generator.el
@@ -731,7 +731,10 @@ iter-do
(,it-symbol ,iterator))
(while (not ,done-symbol)
(condition-case ,condition-symbol
- (setf ,var (iter-next ,it-symbol))
+ ;; Variables that start with an underscore shouldn't be set.
+ ,(if (string-match-p "\\`_" (symbol-name var))
+ nil
+ `(setf ,var (iter-next ,it-symbol)))
(iter-end-of-sequence
(setf ,result-symbol (cdr ,condition-symbol))
(setf ,done-symbol t)))
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
- bug#31641: 26.1; iter-do variable not left unused warning,
Lars Ingebrigtsen <=