anchor.diff:  			:literal form :types '((body))))
   	  ((symbolp form)		;function call
   	   (compile-funcall form))
  -	  (t (bst-compile-error "Illegal form in BST function body: ~S" form)))))))
  +	  (t (bst-compile-error "Illegal form in BST function body: ~:S" form)))))))
   
   (defun bst-compile-defun (name function-definition)
     "Compile a BST wizard-defined function of given NAME and
  
positive.code:     ((eql a t) t)
      ((eql b t) t)
      (t (union a b))))
  
  (defun type<= (a b)
    (cond
  
negative.code: 	(let ((top-mvform (pop *form-stack*)))
  	  (labels ((return-the-form ()
  		     (let* ((available-type (car (mvform-types top-mvform)))
  			    (lisp-form (mvform-form top-mvform))
  			    (side-effects (mvform-side-effects top-mvform)))
  		     (multiple-value-bind (coerced-form effective-type)
  			 (coerce-form lisp-form available-type type)
  		       (return-from pop-form
  			 (values coerced-form effective-type side-effects))))))
  	    (cond
  	      ((not (null (intersection assigned-variables
  					(side-effects-used-variables
  