Note that :custom-show is obsolete.

Fixes: debbugs:75

lisp/ChangeLog

 2011-07-07  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
+	* cus-edit.el (custom-show): Marked as obsolete.
+
 	* net/network-stream.el (network-stream-open-starttls): If gnutls
 	negotiation fails, then possibly try again with a non-encrypted
 	connection (bug#9017).

lisp/cus-edit.el

@@ -1829,6 +1829,7 @@ item in another window.\n\n"))
 ;; We want simple widgets to be displayed by default, but complex
 ;; widgets to be hidden.
 
+;; This widget type is obsolete as of Emacs 24.1.
 (widget-put (get 'item 'widget-type) :custom-show t)
 (widget-put (get 'editable-field 'widget-type)
 	    :custom-show (lambda (_widget value)
@@ -2257,6 +2258,7 @@ and `face'."
 	     (setq widget nil)))))
   (widget-setup))
 
+(make-obsolete 'custom-show "this widget type is no longer supported." "24.1")
 (defun custom-show (widget value)
   "Non-nil if WIDGET should be shown with VALUE by default."
   (let ((show (widget-get widget :custom-show)))