anchor.diff:                   (block ,name
                      ,@real-body)))))))))
   
  -
  -
   (defmacro define-default-presentation-method (name &rest args)
     (let ((gf (gethash name *presentation-gf-table*)))
       (unless gf
  
positive.code:             #',(generic-function-name gf)
              ,(type-arg-position gf)
              ,@args)))
  
  
  ;;; Used by map-over-presentation-type-supertypes as well
  
  
negative.code:       (multiple-value-bind (qualifiers lambda-list decls body)
            (parse-method-body args)
          (let ((type-arg (nth (1- (type-arg-position gf)) lambda-list)))
            (with-current-source-form (type-arg)
              (unless (consp type-arg)
                (error "Type argument in presentation method must be ~
                        specialized"))
              (unless (eq (car type-arg)  'type)
                (error "Type argument mismatch with presentation generic ~
                        function definition")))
            (destructuring-bind (type-var type-name) type-arg
              (let* ((method-ll `((,(type-key-arg gf)
                                   ,(ptype-specializer type-name))
  