anchor.diff:    (let* ((classes (mapcar #'class-of
                             (required-portion gf args)))
            (applicable-methods
  -          (compute-applicable-methods-using-classes gf classes))
  -         (emfun (std-compute-effective-method-function gf applicable-methods)))
  -    (setf (gethash class (classes-to-emf-table gf)) emfun)
  -    (funcall emfun args)))
  +          (compute-applicable-methods-using-classes gf classes)))
  +    (when (null applicable-methods)
  +      (error "No applicable methods to generic function ~S.
  +Dispatching on class ~S." gf class))
  +    (let ((emfun (std-compute-effective-method-function gf applicable-methods)))
  +      (setf (gethash class (classes-to-emf-table gf)) emfun)
  +      (funcall emfun args))))
   
   ;;; compute-applicable-methods-using-classes
   
  
positive.code:     (character                                     (find-class 'character))
      (hash-table                                    (find-class 'hash-table))
      (package                                       (find-class 'package))
      ;;(pathname                                      (find-class 'pathname))
      ;;(readtable                                     (find-class 'readtable))
      (synonym-stream                                (find-class 'synonym-stream))
      (stream                                        (find-class 'stream))
  
negative.code:   (let ((primaries (remove-if-not #'primary-method-p methods))
          (around (find-if #'around-method-p methods)))
      (when (null primaries)
        (error "No primary methods for the generic function ~S. Called with " gf))
      (if around
          (let ((next-emfun
                  (funcall
  