[sh-script] Erroneous syntax highlighting of "[[ ]]" expressions with zsh

[jerome]

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In GNU Emacs 21.4.1 (x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2005-10-04 on athlon, modified by Debian
configured using `configure '--build=x86_64-linux-gnu' 
'--host=x86_64-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' 
'--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' 
'--mandir=/usr/share/man' '--with-pop=yes' '--with-x=yes' 
'--with-x-toolkit=athena' 'CFLAGS=-DDEBIAN -g -O2' 
'build_alias=x86_64-linux-gnu' 'host_alias=x86_64-linux-gnu''
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: fr_FR.UTF-8
  locale-coding-system: utf-8
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

This is Debian bug #335712 
(http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=335712)

Thanks in advance.

----------------------------

Consider the following file

#!/bin/zsh
if [[ x == x ]] then
  echo OK
fi
if [[ x == x ]]; then
  echo OK
fi

opened in Shell-script[zsh] mode. The first "then" is not colored
(but the second one is).

Moreover, in the condition "x == x", the first x is colored (this
is incorrect, IMHO), while the second one isn't (OK).

----------------------------

It seems that bash makes the ";" mandatory after "]]" while zsh does
not.


Recent input:
s SPC i n SPC a d v a n c e . <return> <return> C h 
e e r s , <down-mouse-1> <mouse-1> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <down-mouse-1> 
<mouse-1> SPC D a n i e l <down-mouse-1> <mouse-1> 
<backspace> ? C-c C-c , i M-u q g <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
SPC SPC q <help-echo> <help-echo> M-x C-h C-g C-g C-g 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <menu-bar> <help-menu> <re
port-emacs-bug>

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