; elisp-scope.el: Fix error during widget args analysis

* lisp/emacs-lisp/elisp-scope.el (elisp-scope--match-spec-to-arg):
Simplify and fix handling of empty list.

* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el:
Add test.

lisp/emacs-lisp/elisp-scope.el

@@ -2685,8 +2685,7 @@ ARGS bound to the analyzed arguments."
   (let ((symbols-with-pos-enabled t)) (and (member arg (cdr spec)) t)))
 
 (cl-defmethod elisp-scope--match-spec-to-arg ((spec (head plist)) arg)
-  (cond
-   ((consp arg)
+  (when (listp arg)
     (let ((res nil) (go t))
       (while (and arg go)
         (let* ((key (car arg))
@@ -2695,17 +2694,14 @@ ARGS bound to the analyzed arguments."
           (push (if (keywordp bkw) '(symbol . constant) t) res)
           (push (setq go (elisp-scope--match-spec-to-arg (alist-get bkw (cdr spec) t) val)) res))
         (setq arg (cddr arg)))
-      (when go (cons 'list (nreverse res)))))
-   ((null arg) t)))
+      (when go (cons 'list (nreverse res))))))
 
 (cl-defmethod elisp-scope--match-spec-to-arg ((spec (head list)) arg)
-  (cond
-   ((consp arg)
+  (when (listp arg)
     (let ((specs (cdr spec)) (go t) res)
       (while (and specs (setq go (elisp-scope--match-spec-to-arg (pop specs) (pop arg))))
         (push go res))
-      (when go (cons 'list (nreverse res)))))
-   ((null arg) t)))
+      (when go (cons 'list (nreverse res))))))
 
 (cl-defmethod elisp-scope--match-spec-to-arg ((spec (head plist-and-then)) arg)
   (cond

test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el

@@ -150,6 +150,13 @@
                           )))
   :version "29.1")
 
+;; Taken from browse-url.el:
+(defcustom baz-opt 'browse-url-mail
+  "Baz."
+  :type '(function-item :tag "Emacs Mail" :value browse-url-mail))
+;;        ^ elisp-widget-type
+;;                                         ^ (elisp-constant font-lock-builtin-face)
+
 (e-s-analyze-form #'ignore)
 ;; ^ (elisp-shorthand-font-lock-face elisp-function)
 ;;   ^ elisp-function