bug#26960: 26.0.50; Complaints about unused variable in cl-destructuring-bind

[Philipp Stephani <p.stephani2@gmail.com>]

Create a file with the following contents (here /tmp/destr.el):

;;; -*- lexical-binding: t; -*-
(require 'cl-lib)
(cl-destructuring-bind (&whole a b &rest _) '(1 2)
  (print (list a b)))

Then run

emacs -Q -batch -f batch-byte-compile /tmp/destr.el

The byte compiler will complain:

In toplevel form:
/tmp/destr.el:3:1:Warning: variable ‘_’ not left unused

even though the variable is clearly unused.


In GNU Emacs 26.0.50 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.10.8)
 of 2017-05-17 built on localhost
Repository revision: f7c07930b581b1bcfdfb1874b6883233516bdf11
Windowing system distributor 'The X.Org Foundation', version 11.0.11803000
System Description:	Ubuntu 14.04 LTS

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --without-pop --with-mailutils --enable-checking
 --enable-check-lisp-object-type --with-modules 'CFLAGS=-O0 -ggdb3''

Configured features:
XPM JPEG TIFF GIF PNG SOUND GSETTINGS NOTIFY GNUTLS FREETYPE XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message subr-x puny seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils time-date mule-util
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite charscript charprop case-table epa-hook jka-cmpr-hook
help simple abbrev obarray minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote inotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty
make-network-process emacs)

Memory information:
((conses 16 94336 9026)
 (symbols 48 20116 1)
 (miscs 40 39 145)
 (strings 32 17446 3603)
 (string-bytes 1 571028)
 (vectors 16 13884)
 (vector-slots 8 481230 5848)
 (floats 8 48 108)
 (intervals 56 216 0)
 (buffers 976 12)
 (heap 1024 34121 952))

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