Toio little error information from widgets

["Lennart Borgman (gmail)" <lennart.borgman@gmail.com>]

The following code has an error. This error is however very hard to 
detect. I do not get a traceback, it just behaves very strange.

Try the following:

   emacs -Q
   (eval the code below)
   M-x customize-option RET temp-cust2 RET

Then click INS. It does not work as I expect. (To get it working 
uncomment the line

   ;;(or (eq value 'fundamental-mode)

and the corresponding ")" in the code.

What could be done about this?

Here is the code:

(defun major-modep(value)
   (let ((sym-name (symbol-name value)))
     ;; Do some reasonable test to find out if it is a major mode.
     ;; Load autoloaded mode functions.
     ;;
     ;; Fix-me: Maybe test for minor modes? How was that done?
     (when (and (fboundp value)
                (< 5 (length sym-name))
                (string= "-mode" (substring sym-name (- (length 
sym-name) 5)))
                (if (and (listp (symbol-function value))
                         (eq 'autoload (car (symbol-function value))))
                    (progn
                      (message "loading ")
                      (load (cadr (symbol-function value)) t t))
                  t)
                ;;(or (eq value 'fundamental-mode)
                    (intern-soft (concat sym-name "-hook"))
                    (boundp (intern-soft (concat sym-name "-hook"))))
                ;;)
       t)))

(define-widget 'major-mode-function2 'function
   "A major mode lisp function."
   :complete-function (lambda ()
		       (interactive)
		       (lisp-complete-symbol 'major-modep))
   :prompt-match 'major-modep
   :prompt-history 'widget-function-prompt-value-history
   :match-alternatives '(major-modep)
   :validate (lambda (widget)
	      (unless (major-modep (widget-value widget))
		(widget-put widget :error (format "Invalid function: %S"
						  (widget-value widget)))
		widget))
   :value 'fundamental-mode
   :tag "Major mode function")

(defcustom temp-cust2 nil
   "doc"
   :type '(alist :key-type major-mode-function2
                 :value-type (set
                              (list :tag "Highlighting on" (const hion) 
boolean)
                              (list :tag "Highlighting" (const hili) 
function)
                              (list :tag "Goto" (const goto) function)
                              (list :tag "Next" (const next) function)
                              (list :tag "Prev" (const next) function)
                              )))