Problems with SLOT-VALUE-USING-CLASS and CLOS

[arleth@gate.fzi.de (Bernd Wild)]

The problem description given yesterday was a bit to simplified.
The code example leaves out a neccessary part which leads to the 
specified error.

Corrected version of code example:

(defclass my-metaclass (standard-class)
   ((class-slot :accessor metaclass-class-slot))
   )

(defclass my-class-mixin ()
   ((slot1 :accessor slot1)))

(defclass my-class1 (my-class-mixin)
   ((slot2 :accessor slot2))
   (:metaclass my-metaclass))

(make-instance 'my-class1) ==> #<MY-METACLASS ...>

(defmethod slot-value-using-class :around 
           ((class my-metaclass) object slot)
   (let ((result nil))
      (setf result (call-next-method))
      result))

(defclass my-class2 (my-class-mixin)
   ((slot2 :accessor slot2))
   (:metaclass my-metaclass))

(make-instance 'my-class2) ==> NIL

The automatic generated constructor method for MY-CLASS2 has a body
which only contains NIL instead of allocating a structure for this instance etc.

Can anybody help me?

Ekkehard Arleth

email: arleth@fzi.de