bug#11811: 23.2; Macro pushnew in cl.el captures variable x

[Janne Nykopp]

Evaluating the following forms triggers a lisp error:
(require 'cl)
(let ((x (list 1 2 3)))
  (pushnew 'a x))

Evaluating in *scratch* buffer results in the following debugger
backtrace:
Debugger entered--Lisp error: (wrong-type-argument listp a)
  memql(a a)
  (if (memql x x) x (setq x (cons x x)))
  (let ((x ...)) (if (memql x x) x (setq x ...)))
  (pushnew (quote a) x)
  (let ((x ...)) (pushnew (quote a) x))
  eval((let ((x ...)) (pushnew (quote a) x)))
  eval-last-sexp-1(t)
  eval-last-sexp(t)
  eval-print-last-sexp()
  call-interactively(eval-print-last-sexp nil nil)

The macro `pushnew' seems to capture variable x when no keyword
arguments are given:
(macroexpand '(pushnew 'a x)) =>
(let ((x (quote a))) (if (memql x x) x (setq x (cons x x))))

This bug still exists in emacs-24 developer branch cl.el revision
108062 (latest version at the time of writing).



Information collected by M-x report-emacs-bug follows.

In GNU Emacs 23.2.1 (i486-pc-linux-gnu, GTK+ Version 2.20.0)
 of 2010-12-11 on raven, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
configured using `configure  '--build' 'i486-linux-gnu' '--build' 
'i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' 
'--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' 
'--mandir=/usr/share/man' '--with-pop=yes' 
'--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.2/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.2/leim'
 '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 
'build_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g' 'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-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-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<help-echo> <help-echo> ( r e q u i r e SPC ' c l ) 
<return> <backspace> C-j ( l e t SPC ( ( x SPC ( l 
i s t SPC 1 SPC 3 SPC 4 <backspace> <backspace> <backspace> 
2 SPC 4 ) <backspace> <backspace> 3 ) ) ) <return> 
<tab> ( p u s h n e w SPC ' a SPC x ) ) C-j q M-x r 
e p o r t - <tab> <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Entering debugger...
Back to top level.

Load-path shadows:
/usr/share/emacs/23.2/site-lisp/debian-startup hides 
/usr/share/emacs/site-lisp/debian-startup
/usr/share/emacs/23.2/site-lisp/dictionaries-common/ispell hides 
/usr/share/emacs/23.2/lisp/textmodes/ispell
/usr/share/emacs/23.2/site-lisp/dictionaries-common/flyspell hides 
/usr/share/emacs/23.2/lisp/textmodes/flyspell

Features:
(shadow sort mail-extr message sendmail regexp-opt ecomplete rfc822 mml
mml-sec password-cache mm-decode mm-bodies mm-encode mailcap mail-parse
rfc2231 rfc2047 rfc2045 qp ietf-drums mailabbrev nnheader gnus-util
netrc time-date mm-util mail-prsvr gmm-utils wid-edit mailheader canlock
sha1 hex-util hashcash mail-utils emacsbug help-mode easymenu view debug
cl cl-19 tooltip ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd
font-setting tool-bar dnd fontset image fringe lisp-mode register page
menu-bar rfn-eshadow timer select scroll-bar mldrag mouse jit-lock
font-lock syntax facemenu font-core frame cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew
greek romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev loaddefs button
minibuffer faces cus-face files text-properties overlay md5 base64
format env code-pages mule custom widget hashtable-print-readable
backquote make-network-process dbusbind system-font-setting
font-render-setting gtk x-toolkit x multi-tty emacs)