anchor.diff:          (list x))
   	  (expex-make-%setq ex '~%ret x)))
   
  -(defun expex-make-setq-copy (ex x s)
  +(defun expex-copy-%setq (ex x s)
     (? (eq s (second x.))
        x
        `(,x.
  
positive.code: 
  (defun expression-expand (ex x)
    (when x
  	(with-temporary *current-expex* ex
  	  (with-temporary *expex-funinfo* (transpiler-global-funinfo *current-transpiler*)
          (expex-body ex x)))))
  
negative.code: 			   (? (%setq? last.)
  				  (? (eq s (second last.))
  				     (expex-guest-filter-setter ex last.)
  				     (expex-copy-%setq ex last s))
  				  (expex-make-%setq ex s last.)))
  		x)))
  
  