anchor.diff:  		(!return (ret) `,`(return-from ,',blockname ,(or ret :undefined))))
          (lambda (js-user::this
   		&optional ,@(mapcar (lambda (arg)
  -				      `(,(->usersym arg) :undefined)) args)
  +				      `(,(->usersym arg) :undefined-unset)) args)
   		&rest ,additional-args)
   	 (let (js-user::arguments)
   	   (let (,@(mapcar (lambda (var)
  
positive.code: 	 (get-arr (gensym))
  	 (set-arr (gensym))
  	 (inst (gensym))
  	 (len (length vars)))
      `(let ((,get-arr
  	    (make-array ,(1+ len)
  			:element-type 'function
  			:initial-contents
  
negative.code: 					(declare (ignore n))
  					(setf ,var val)))
  				   vars)
  			 (lambda (n val) (setf (nth (- n ,len) ,oth) val)))))
  	    (,inst (make-instance 'arguments
  				   :vlen ,len
  				   :length (+ ,argument-cnt (length ,oth))
  				   :get-arr ,get-arr :set-arr ,set-arr)))
         (add-sealed-property ,inst
  			    "length"
  			    (lambda (-)
  			      (declare (ignore -))
  			      (+ ,argument-cnt (length ,oth))))
         ,inst)))
  
  
  