anchor.diff:                                      (cdddr varrec))))
             (varrec-attr-set! varrec 'closure-stack
                               (acons depth local-varrec closure-stack))
  -          (varrec-attr-set! varrec 'boxed (varrec-written? varrec))
  +          (varrec-attr-set! varrec 'boxed (varrec-quasi-written? varrec))
             (rplaca closure-cell (cons local-varrec (car closure-cell)))
             local-varrec))))
   
  
positive.code:     ;; closure.  instead we use a special self-closure attr.
      (let* ((self-varrec (attr-ref attrs 'self)))
        (form-attr-set! form 'self-closure
                        (if (and self-varrec (not (varrec-written? self-varrec)))
                            (resolve-closure-var self-varrec (1+ depth)
                                                 self-closure-cell)
                            false)))
  
negative.code:            (written false))
        (cond ((= state 2) 
               (set! written true))
              ((early-access-state? state)
               (set! written (if (= 3 state) 'early-read true))
               (rplacd (cdr form) (cons (list 'define varrec (quoted-unspecified))
                                        (cddr form))))
              ((= state 5)
               (error "bad variable ~S" (car varrec))))
        (varrec-attr-set! varrec 'written written))))
  
  