bug#8253: 23.2; variable-at-point on ' of 'foo

[Kevin Ryde <user42@zip.com.au>]

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When point is on the ' of a 'foo quoted variable, M-x describe-variable
doesn't offer that variable as a default, and `variable-at-point'
doesn't return it.  Eg.

    (set 'baud-rate 9600)
         ^---point here
    M-: (variable-at-point)
    => 0

where I hoped it would return `baud-rate', as it does if point is on say
the "b".

I strike this when using backward/forward sexp to move between args
since that leaves point on the '.  It'd be good if variable-at-point
allowed/recognised that.

In the code there's a

    (skip-chars-forward "'")

which looks like it's supposed to do this, but it's after the bit going
to the start of the word and seems to be defeated by (forward-sexp -1).
Actually that ends up going to the previous sexp, so if you've got

    (list 'emacs-version
             'baud-rate)
             ^---point here

then it returns the preceding `emacs-version' instead of `baud-rate'.

Perhaps the change below.  bzr has still defeated me, or I would try a
diff with it :-(

2011-03-14  Kevin Ryde  <user42@zip.com.au>

	* help-fns.el (variable-at-point): Skip forward across ' first, to
	allow point on the ' part of quoted 'emacs-version etc.  Helps
	when moving by sexps which leaves point on the ' instead of the
	variable name as such.


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--- help-fns.el.~1.146.~	2009-11-17 17:24:19.000000000 +1100
+++ help-fns.el	2011-03-15 09:48:49.000000000 +1100
@@ -527,11 +527,11 @@
   (with-syntax-table emacs-lisp-mode-syntax-table
     (or (condition-case ()
 	    (save-excursion
+	      (skip-chars-forward "'")
 	      (or (not (zerop (skip-syntax-backward "_w")))
 		  (eq (char-syntax (following-char)) ?w)
 		  (eq (char-syntax (following-char)) ?_)
 		  (forward-sexp -1))
-	      (skip-chars-forward "'")
 	      (let ((obj (read (current-buffer))))
 		(and (symbolp obj) (boundp obj) obj)))
           (error nil))

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In GNU Emacs 23.2.1 (i486-pc-linux-gnu, GTK+ Version 2.20.0)
 of 2010-05-16 on raven, modified by Debian
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_AU
  value of $XMODIFIERS: nil
  locale-coding-system: iso-latin-1-unix
  default enable-multibyte-characters: t