Slots of a class with a custom meta-class are reported as unbound.

[stassats]

(defpackage test2
  (:use :cl :mop))

(in-package test2)

(defclass storable-class (standard-class)
  ())

(defmethod validate-superclass
    ((class standard-class) (superclass storable-class))
  t)

(defmethod validate-superclass
    ((class storable-class) (superclass standard-class))
  t)

;;;

(defclass identifiable ()
  ((id :accessor id
       :initform 1))
  (:metaclass storable-class))

ID slot is unbound and bound at the same time, despite having an
initform.

(describe (make-instance 'identifiable))
#<IDENTIFIABLE {181F4B24}> is an instance of #<STORABLE-CLASS IDENTIFIABLE {1E4B2D10}>.
The following slots have :INSTANCE allocation:

ID unbound

(slot-boundp (make-instance 'identifiable) 'id)
=>
NIL

(slot-value (make-instance 'identifiable) 'id)
=>
1

[stassats]

Apparently, this has been fixed in ticket:14154

[stassats]

Meaning changeset:14154