anchor.diff:                                     ,name-string
                                      ,interface
                                      ',parameter-types
  +                                   ',parameter-names
                                      (lambda (,@parameter-names)
                                        ,@body))))
   
  
positive.code: (defclass method-handler (handler)
    ((output-signature :initarg :output-signature :reader handler-output-signature)))
  
  (defun register-dbus-method (object-name method-name name-string interface parameter-types return-types handler)
    (check-type method-name symbol)
    (check-type name-string string)
    (check-type interface string)
  
negative.code:                            ,name-string
                             ,interface
                             ',parameter-types
                             ',parameter-names
                             ',return-types
                             (lambda (,@parameter-names)
                               ,@body))))
  