Leslie P. Polzer writes:
> (defclass pineapple () ()
> (:metaclass persistent-metaclass))
> (let ((fruit (make-instance 'pineapple)))
> (defclass pineapple ()
> ((tree :initform 1))
> (:metaclass persistent-metaclass))
> (slot-value fruit 'tree)))
>
> Will raise unbound slot hell with current code if you have
> a lot of instances. Backends signal UNBOUND-SLOT instead
> of calling SLOT-UNBOUND (which is the more conformant option
> as I see it from CLHS and the MOP spec).
>
> This is also better "do what I mean" behaviour; normally
> when you provide an initform for a slot you rely on never
> having to deal with unbound slots (at least I do).
>
> Attached is a patch which tests this, changes the backend behaviour
> and provides a default for SLOT-UNBOUND that uses the initform
> to fill in the slot value.
This is probably bad: you can't SLOT-MAKUNBOUND anymore. I have not
yet read and understood all about CLHS 4.3.6.2 but something along
UPDATE-INSTANCE-FOR-REDEFINED-CLASS looks like what's needed.
I can't test it here but the test would look like:
(deftest slot-unbound
(progn
(defclass pineapple () ()
(:metaclass persistent-metaclass))
(let ((fruit (make-instance 'pineapple)))
(defclass pineapple ()
((tree :initform 1))
(:metaclass persistent-metaclass))
(values (slot-value fruit 'tree)
(progn (slot-makunbound fruit 'tree)
(signals-specific-condition (unbound-slot)
(slot-value inst 'slot1))))))
1 t)
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