(describe-function): Handle the arglist of a macro.

lisp/help.el

@@ -565,10 +565,13 @@ C-w Display information on absence of warranty for GNU Emacs."
 		(princ "'")))
 	  (princ ".")
 	  (terpri)
-	  (let ((arglist (cond ((byte-code-function-p def)
-				(car (append def nil)))
-			       ((eq (car-safe def) 'lambda)
-				(nth 1 def))
+	  (let* ((inner-function (if (and (listp def) 'macro)
+				     (cdr def)
+				   def))
+		 (arglist (cond ((byte-code-function-p inner-function)
+				(car (append inner-function nil)))
+			       ((eq (car-safe inner-function) 'lambda)
+				(nth 1 inner-function))
 			       (t t))))
 	    (if (listp arglist)
 		(progn