anchor.diff:                                   (second form)))
       (dolist* ((var . value) (binds let))
         (declare (ignore value))
  -      (setf env (register env :let var :dummy)))
  +      (extend env :let var :dummy))
       (multiple-value-setf ((body let) nil (declares let)) (walk-implict-progn let (cddr form) env :declare t))))
   
   (defclass let*-form (variable-binding-form)
  
positive.code: 
  (defwalker-handler tagbody (form parent env)
    (with-form-object (tagbody tagbody-form :parent parent :source form :body (cdr form))
      (setf env (register env :tagbody 'enclosing-tagbody tagbody))
      (flet ((go-tag-p (form)
               (or (symbolp form) (integerp form))))
        ;; the loop below destructuivly modifies the body of tagbody,
  
negative.code:       (loop
           for part on (body tagbody)
           if (go-tag-p (car part))
             do (extend env :tag (car part) (cdr part)))
        (loop
           for part on (body tagbody)
           if (go-tag-p (car part))
  