Simplified bug 214.

[sbcl/lichteblau.git] / src / pcl / std-class.lisp

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.

;;;; This software is derived from software originally released by Xerox
;;;; Corporation. Copyright and release statements follow. Later modifications
;;;; to the software are in the public domain and are provided with
;;;; absolutely no warranty. See the COPYING and CREDITS files for more
;;;; information.

;;;; copyright information from original PCL sources:
;;;;
;;;; Copyright (c) 1985, 1986, 1987, 1988, 1989, 1990 Xerox Corporation.
;;;; All rights reserved.
;;;;
;;;; Use and copying of this software and preparation of derivative works based
;;;; upon this software are permitted. Any distribution of this software or
;;;; derivative works must comply with all applicable United States export
;;;; control laws.
;;;;
;;;; This software is made available AS IS, and Xerox Corporation makes no
;;;; warranty about the software, its performance or its conformity to any
;;;; specification.

(in-package "SB-PCL")
\f
(defmethod slot-accessor-function ((slotd effective-slot-definition) type)
  (ecase type
    (reader (slot-definition-reader-function slotd))
    (writer (slot-definition-writer-function slotd))
    (boundp (slot-definition-boundp-function slotd))))

(defmethod (setf slot-accessor-function) (function
                                          (slotd effective-slot-definition)
                                          type)
  (ecase type
    (reader (setf (slot-definition-reader-function slotd) function))
    (writer (setf (slot-definition-writer-function slotd) function))
    (boundp (setf (slot-definition-boundp-function slotd) function))))

(defconstant +slotd-reader-function-std-p+ 1)
(defconstant +slotd-writer-function-std-p+ 2)
(defconstant +slotd-boundp-function-std-p+ 4)
(defconstant +slotd-all-function-std-p+ 7)

(defmethod slot-accessor-std-p ((slotd effective-slot-definition) type)
  (let ((flags (slot-value slotd 'accessor-flags)))
    (declare (type fixnum flags))
    (if (eq type 'all)
        (eql +slotd-all-function-std-p+ flags)
        (let ((mask (ecase type
                      (reader +slotd-reader-function-std-p+)
                      (writer +slotd-writer-function-std-p+)
                      (boundp +slotd-boundp-function-std-p+))))
          (declare (type fixnum mask))
          (not (zerop (the fixnum (logand mask flags))))))))

(defmethod (setf slot-accessor-std-p) (value
                                       (slotd effective-slot-definition)
                                       type)
  (let ((mask (ecase type
                (reader +slotd-reader-function-std-p+)
                (writer +slotd-writer-function-std-p+)
                (boundp +slotd-boundp-function-std-p+)))
        (flags (slot-value slotd 'accessor-flags)))
    (declare (type fixnum mask flags))
    (setf (slot-value slotd 'accessor-flags)
          (if value
              (the fixnum (logior mask flags))
              (the fixnum (logand (the fixnum (lognot mask)) flags)))))
  value)

(defmethod initialize-internal-slot-functions ((slotd
                                                effective-slot-definition))
  (let* ((name (slot-value slotd 'name))
         (class (slot-value slotd 'class)))
    (let ((table (or (gethash name *name->class->slotd-table*)
                     (setf (gethash name *name->class->slotd-table*)
                           (make-hash-table :test 'eq :size 5)))))
      (setf (gethash class table) slotd))
    (dolist (type '(reader writer boundp))
      (let* ((gf-name (ecase type
                              (reader 'slot-value-using-class)
                              (writer '(setf slot-value-using-class))
                              (boundp 'slot-boundp-using-class)))
             (gf (gdefinition gf-name)))
        (compute-slot-accessor-info slotd type gf)))
    (initialize-internal-slot-gfs name)))

(defmethod compute-slot-accessor-info ((slotd effective-slot-definition)
                                       type gf)
  (let* ((name (slot-value slotd 'name))
         (class (slot-value slotd 'class))
         (old-slotd (find-slot-definition class name))
         (old-std-p (and old-slotd (slot-accessor-std-p old-slotd 'all))))
    (multiple-value-bind (function std-p)
        (if (eq *boot-state* 'complete)
            (get-accessor-method-function gf type class slotd)
            (get-optimized-std-accessor-method-function class slotd type))
      (setf (slot-accessor-std-p slotd type) std-p)
      (setf (slot-accessor-function slotd type) function))
    (when (and old-slotd (not (eq old-std-p (slot-accessor-std-p slotd 'all))))
      (push (cons class name) *pv-table-cache-update-info*))))

(defmethod slot-definition-allocation ((slotd structure-slot-definition))
  :instance)
\f
(defmethod shared-initialize :after ((object documentation-mixin)
                                     slot-names
                                     &key (documentation nil documentation-p))
  (declare (ignore slot-names))
  (when documentation-p
    (setf (plist-value object 'documentation) documentation)))

;;; default if DOC-TYPE doesn't match one of the specified types
(defmethod documentation (object doc-type)
  (warn "unsupported DOCUMENTATION: type ~S for object ~S"
        doc-type
        (type-of object))
  nil)

;;; default if DOC-TYPE doesn't match one of the specified types
(defmethod (setf documentation) (new-value object doc-type)
  ;; CMU CL made this an error, but since ANSI says that even for supported
  ;; doc types an implementation is permitted to discard docs at any time
  ;; for any reason, this feels to me more like a warning. -- WHN 19991214
  (warn "discarding unsupported DOCUMENTATION of type ~S for object ~S"
        doc-type
        (type-of object))
  new-value)

(defmethod documentation ((object documentation-mixin) doc-type)
  (declare (ignore doc-type))
  (plist-value object 'documentation))

(defmethod (setf documentation) (new-value
                                 (object documentation-mixin)
                                 doc-type)
  (declare (ignore doc-type))
  (setf (plist-value object 'documentation) new-value))

(defmethod documentation ((slotd standard-slot-definition) doc-type)
  (declare (ignore doc-type))
  (slot-value slotd 'documentation))

(defmethod (setf documentation) (new-value
                                 (slotd standard-slot-definition)
                                 doc-type)
  (declare (ignore doc-type))
  (setf (slot-value slotd 'documentation) new-value))
\f
;;;; various class accessors that are a little more complicated than can be
;;;; done with automatically generated reader methods

(defmethod class-finalized-p ((class pcl-class))
  (with-slots (wrapper) class
    (not (null wrapper))))

(defmethod class-prototype ((class std-class))
  (with-slots (prototype) class
    (or prototype (setq prototype (allocate-instance class)))))

(defmethod class-prototype ((class structure-class))
  (with-slots (prototype wrapper defstruct-constructor) class
    (or prototype
        (setq prototype
              (if defstruct-constructor
                  (allocate-instance class)
                  (allocate-standard-instance wrapper))))))

(defmethod class-direct-default-initargs ((class slot-class))
  (plist-value class 'direct-default-initargs))

(defmethod class-default-initargs ((class slot-class))
  (plist-value class 'default-initargs))

(defmethod class-slot-cells ((class std-class))
  (plist-value class 'class-slot-cells))
\f
;;;; class accessors that are even a little bit more complicated than those
;;;; above. These have a protocol for updating them, we must implement that
;;;; protocol.

;;; Maintaining the direct subclasses backpointers. The update methods are
;;; here, the values are read by an automatically generated reader method.
(defmethod add-direct-subclass ((class class) (subclass class))
  (with-slots (direct-subclasses) class
    (pushnew subclass direct-subclasses)
    subclass))
(defmethod remove-direct-subclass ((class class) (subclass class))
  (with-slots (direct-subclasses) class
    (setq direct-subclasses (remove subclass direct-subclasses))
    subclass))

;;; Maintaining the direct-methods and direct-generic-functions backpointers.
;;;
;;; There are four generic functions involved, each has one method for the
;;; class case and another method for the damned EQL specializers. All of
;;; these are specified methods and appear in their specified place in the
;;; class graph.
;;;
;;;   ADD-DIRECT-METHOD
;;;   REMOVE-DIRECT-METHOD
;;;   SPECIALIZER-DIRECT-METHODS
;;;   SPECIALIZER-DIRECT-GENERIC-FUNCTIONS
;;;
;;; In each case, we maintain one value which is a cons. The car is the list
;;; methods. The cdr is a list of the generic functions. The cdr is always
;;; computed lazily.
(defmethod add-direct-method ((specializer class) (method method))
  (with-slots (direct-methods) specializer
    (setf (car direct-methods) (adjoin method (car direct-methods))     ;PUSH
          (cdr direct-methods) ()))
  method)
(defmethod remove-direct-method ((specializer class) (method method))
  (with-slots (direct-methods) specializer
    (setf (car direct-methods) (remove method (car direct-methods))
          (cdr direct-methods) ()))
  method)

(defmethod specializer-direct-methods ((specializer class))
  (with-slots (direct-methods) specializer
    (car direct-methods)))

(defmethod specializer-direct-generic-functions ((specializer class))
  (with-slots (direct-methods) specializer
    (or (cdr direct-methods)
        (setf (cdr direct-methods)
              (let (collect)
                (dolist (m (car direct-methods))
                  ;; the old PCL code used COLLECTING-ONCE which used
                  ;; #'EQ to check for newness
                  (pushnew (method-generic-function m) collect :test #'eq))
                (nreverse collect))))))
\f
;;; This hash table is used to store the direct methods and direct generic
;;; functions of EQL specializers. Each value in the table is the cons.
(defvar *eql-specializer-methods* (make-hash-table :test 'eql))
(defvar *class-eq-specializer-methods* (make-hash-table :test 'eq))

(defmethod specializer-method-table ((specializer eql-specializer))
  *eql-specializer-methods*)

(defmethod specializer-method-table ((specializer class-eq-specializer))
  *class-eq-specializer-methods*)

(defmethod add-direct-method ((specializer specializer-with-object)
                              (method method))
  (let* ((object (specializer-object specializer))
         (table (specializer-method-table specializer))
         (entry (gethash object table)))
    (unless entry
      (setq entry
            (setf (gethash object table)
                  (cons nil nil))))
    (setf (car entry) (adjoin method (car entry))
          (cdr entry) ())
    method))

(defmethod remove-direct-method ((specializer specializer-with-object)
                                 (method method))
  (let* ((object (specializer-object specializer))
         (entry (gethash object (specializer-method-table specializer))))
    (when entry
      (setf (car entry) (remove method (car entry))
            (cdr entry) ()))
    method))

(defmethod specializer-direct-methods ((specializer specializer-with-object))
  (car (gethash (specializer-object specializer)
                (specializer-method-table specializer))))

(defmethod specializer-direct-generic-functions ((specializer
                                                  specializer-with-object))
  (let* ((object (specializer-object specializer))
         (entry (gethash object (specializer-method-table specializer))))
    (when entry
      (or (cdr entry)
          (setf (cdr entry)
                (let (collect)
                  (dolist (m (car entry))
                    (pushnew (method-generic-function m) collect :test #'eq))
                  (nreverse collect)))))))

(defun map-specializers (function)
  (map-all-classes (lambda (class)
                     (funcall function (class-eq-specializer class))
                     (funcall function class)))
  (maphash (lambda (object methods)
             (declare (ignore methods))
             (intern-eql-specializer object))
           *eql-specializer-methods*)
  (maphash (lambda (object specl)
             (declare (ignore object))
             (funcall function specl))
           *eql-specializer-table*)
  nil)

(defun map-all-generic-functions (function)
  (let ((all-generic-functions (make-hash-table :test 'eq)))
    (map-specializers (lambda (specl)
                        (dolist (gf (specializer-direct-generic-functions
                                     specl))
                          (unless (gethash gf all-generic-functions)
                            (setf (gethash gf all-generic-functions) t)
                            (funcall function gf))))))
  nil)

(defmethod shared-initialize :after ((specl class-eq-specializer)
                                     slot-names
                                     &key)
  (declare (ignore slot-names))
  (setf (slot-value specl 'type) `(class-eq ,(specializer-class specl))))

(defmethod shared-initialize :after ((specl eql-specializer) slot-names &key)
  (declare (ignore slot-names))
  (setf (slot-value specl 'type) `(eql ,(specializer-object specl))))
\f
(defun real-load-defclass (name metaclass-name supers slots other)
  (let ((res (apply #'ensure-class name :metaclass metaclass-name
                    :direct-superclasses supers
                    :direct-slots slots
                    :definition-source `((defclass ,name)
                                         ,*load-truename*)
                    other)))
    ;; Defclass of a class with a forward-referenced superclass does not
    ;; have a wrapper. RES is the incomplete PCL class. The Lisp class
    ;; does not yet exist. Maybe should return NIL in that case as RES
    ;; is not useful to the user?
    (and (class-wrapper res) (sb-kernel:layout-class (class-wrapper res)))))

(setf (gdefinition 'load-defclass) #'real-load-defclass)

(defun ensure-class (name &rest all)
  (apply #'ensure-class-using-class name (find-class name nil) all))

(defmethod ensure-class-using-class (name (class null) &rest args &key)
  (multiple-value-bind (meta initargs)
      (ensure-class-values class args)
    (setf class (apply #'make-instance meta :name name initargs)
          (find-class name) class)
    class))

(defmethod ensure-class-using-class (name (class pcl-class) &rest args &key)
  (multiple-value-bind (meta initargs)
      (ensure-class-values class args)
    (unless (eq (class-of class) meta) (change-class class meta))
    (apply #'reinitialize-instance class initargs)
    (setf (find-class name) class)
    class))

(defmethod class-predicate-name ((class t))
  'constantly-nil)

(defun fix-super (s)
  (cond ((classp s) s)
        ((not (legal-class-name-p s))
          (error "~S is not a class or a legal class name." s))
        (t
          (or (find-class s nil)
              (setf (find-class s)
                      (make-instance 'forward-referenced-class
                                     :name s))))))

(defun ensure-class-values (class args)
  (let* ((initargs (copy-list args))
         (unsupplied (list 1))
         (supplied-meta   (getf initargs :metaclass unsupplied))
         (supplied-supers (getf initargs :direct-superclasses unsupplied))
         (supplied-slots  (getf initargs :direct-slots unsupplied))
         (meta
           (cond ((neq supplied-meta unsupplied)
                  (find-class supplied-meta))
                 ((or (null class)
                      (forward-referenced-class-p class))
                  *the-class-standard-class*)
                 (t
                  (class-of class)))))
    ;; KLUDGE: It seemed to me initially that there ought to be a way
    ;; of collecting all the erroneous problems in one go, rather than
    ;; this way of solving the problem of signalling the errors that
    ;; we are required to, which stops at the first bogus input.
    ;; However, after playing around a little, I couldn't find that
    ;; way, so I've left it as is, but if someone does come up with a
    ;; better way... -- CSR, 2002-09-08
    (loop for (slot . more) on (getf initargs :direct-slots)
          for slot-name = (getf slot :name)
          if (some (lambda (s) (eq slot-name (getf s :name))) more) 
          ;; FIXME: It's quite possible that we ought to define an
          ;; SB-INT:PROGRAM-ERROR function to signal these and other
          ;; errors throughout the code base that are required to be
          ;; of type PROGRAM-ERROR.
          do (error 'simple-program-error 
                    :format-control "More than one direct slot with name ~S."
                    :format-arguments (list slot-name))
          else 
          do (loop for (option value . more) on slot by #'cddr
                   when (and (member option 
                                     '(:allocation :type 
                                       :initform :documentation))
                             (not (eq unsupplied
                                      (getf more option unsupplied)))) 
                   do (error 'simple-program-error 
                             :format-control "Duplicate slot option ~S for slot ~S."
                             :format-arguments (list option slot-name))))
    (loop for (initarg . more) on (getf initargs :direct-default-initargs)
          for name = (car initarg) 
          when (some (lambda (a) (eq (car a) name)) more) 
          do (error 'simple-program-error 
                    :format-control "Duplicate initialization argument ~
                                     name ~S in :default-initargs of class ~A."
                    :format-arguments (list name class)))
    (loop (unless (remf initargs :metaclass) (return)))
    (loop (unless (remf initargs :direct-superclasses) (return)))
    (loop (unless (remf initargs :direct-slots) (return)))
    (values meta
            (list* :direct-superclasses
                   (and (neq supplied-supers unsupplied)
                        (mapcar #'fix-super supplied-supers))
                   :direct-slots
                   (and (neq supplied-slots unsupplied) supplied-slots)
                   initargs))))
\f

(defmethod shared-initialize :after
           ((class std-class)
            slot-names
            &key (direct-superclasses nil direct-superclasses-p)
                 (direct-slots nil direct-slots-p)
                 (direct-default-initargs nil direct-default-initargs-p)
                 (predicate-name nil predicate-name-p))
  (declare (ignore slot-names))
  (cond (direct-superclasses-p
         (setq direct-superclasses
               (or direct-superclasses
                   (list (if (funcallable-standard-class-p class)
                             *the-class-funcallable-standard-object*
                             *the-class-standard-object*))))
         (dolist (superclass direct-superclasses)
           (unless (validate-superclass class superclass)
             (error "The class ~S was specified as a~%
                     super-class of the class ~S;~%~
                     but the meta-classes ~S and~%~S are incompatible.~@
                     Define a method for ~S to avoid this error."
                     superclass class (class-of superclass) (class-of class)
                     'validate-superclass)))
         (setf (slot-value class 'direct-superclasses) direct-superclasses))
        (t
         (setq direct-superclasses (slot-value class 'direct-superclasses))))
  (setq direct-slots
        (if direct-slots-p
            (setf (slot-value class 'direct-slots)
                  (mapcar (lambda (pl) (make-direct-slotd class pl))
                          direct-slots))
            (slot-value class 'direct-slots)))
  (if direct-default-initargs-p
      (setf (plist-value class 'direct-default-initargs)
            direct-default-initargs)
      (setq direct-default-initargs
            (plist-value class 'direct-default-initargs)))
  (setf (plist-value class 'class-slot-cells)
        (let (collect)
          (dolist (dslotd direct-slots)
            (when (eq :class (slot-definition-allocation dslotd))
              (let ((initfunction (slot-definition-initfunction dslotd)))
                (push (cons (slot-definition-name dslotd)
                               (if initfunction
                                   (funcall initfunction)
                                   +slot-unbound+))
                      collect))))
          (nreverse collect)))
  (setq predicate-name (if predicate-name-p
                           (setf (slot-value class 'predicate-name)
                                 (car predicate-name))
                           (or (slot-value class 'predicate-name)
                               (setf (slot-value class 'predicate-name)
                                     (make-class-predicate-name (class-name
                                                                 class))))))
  (add-direct-subclasses class direct-superclasses)
  (update-class class nil)
  (make-class-predicate class predicate-name)
  (add-slot-accessors class direct-slots))

(defmethod shared-initialize :before ((class class) slot-names &key name)
  (declare (ignore slot-names name))
  ;; FIXME: Could this just be CLASS instead of `(CLASS ,CLASS)? If not,
  ;; why not? (See also similar expression in !BOOTSTRAP-INITIALIZE-CLASS.)
  (setf (slot-value class 'type) `(class ,class))
  (setf (slot-value class 'class-eq-specializer)
        (make-instance 'class-eq-specializer :class class)))

(defmethod reinitialize-instance :before ((class slot-class) &key)
  (remove-direct-subclasses class (class-direct-superclasses class))
  (remove-slot-accessors    class (class-direct-slots class)))

(defmethod reinitialize-instance :after ((class slot-class)
                                         &rest initargs
                                         &key)
  (map-dependents class
                  (lambda (dependent)
                    (apply #'update-dependent class dependent initargs))))

(defmethod shared-initialize :after ((slotd structure-slot-definition)
                                     slot-names
                                     &key (allocation :instance))
  (declare (ignore slot-names))
  (unless (eq allocation :instance)
    (error "Structure slots must have :INSTANCE allocation.")))

(defun make-structure-class-defstruct-form (name direct-slots include)
  (let* ((conc-name (intern (format nil "~S structure class " name)))
         (constructor (intern (format nil "~Aconstructor" conc-name)))
         (defstruct `(defstruct (,name
                                 ,@(when include
                                         `((:include ,(class-name include))))
                                 (:predicate nil)
                                 (:conc-name ,conc-name)
                                 (:constructor ,constructor ())
                                 (:copier nil))
                      ,@(mapcar (lambda (slot)
                                  `(,(slot-definition-name slot)
                                    +slot-unbound+))
                                direct-slots)))
         (reader-names (mapcar (lambda (slotd)
                                 (intern (format nil
                                                 "~A~A reader"
                                                 conc-name
                                                 (slot-definition-name
                                                  slotd))))
                               direct-slots))
         (writer-names (mapcar (lambda (slotd)
                                 (intern (format nil
                                                 "~A~A writer"
                                                 conc-name
                                                 (slot-definition-name
                                                  slotd))))
                               direct-slots))
         (readers-init
           (mapcar (lambda (slotd reader-name)
                     (let ((accessor
                             (slot-definition-defstruct-accessor-symbol
                              slotd)))
                       `(defun ,reader-name (obj)
                         (declare (type ,name obj))
                         (,accessor obj))))
                   direct-slots reader-names))
         (writers-init
           (mapcar (lambda (slotd writer-name)
                     (let ((accessor
                             (slot-definition-defstruct-accessor-symbol
                              slotd)))
                       `(defun ,writer-name (nv obj)
                         (declare (type ,name obj))
                         (setf (,accessor obj) nv))))
                   direct-slots writer-names))
         (defstruct-form
             `(progn
               ,defstruct
               ,@readers-init ,@writers-init
               (cons nil nil))))
    (values defstruct-form constructor reader-names writer-names)))

(defmethod shared-initialize :after
      ((class structure-class)
       slot-names
       &key (direct-superclasses nil direct-superclasses-p)
            (direct-slots nil direct-slots-p)
            direct-default-initargs
            (predicate-name nil predicate-name-p))
  (declare (ignore slot-names direct-default-initargs))
  (if direct-superclasses-p
      (setf (slot-value class 'direct-superclasses)
            (or direct-superclasses
                (setq direct-superclasses
                      (and (not (eq (class-name class) 'structure-object))
                           (list *the-class-structure-object*)))))
      (setq direct-superclasses (slot-value class 'direct-superclasses)))
  (let* ((name (class-name class))
         (from-defclass-p (slot-value class 'from-defclass-p))
         (defstruct-p (or from-defclass-p (not (structure-type-p name)))))
    (if direct-slots-p
        (setf (slot-value class 'direct-slots)
              (setq direct-slots
                    (mapcar (lambda (pl)
                              (when defstruct-p
                                (let* ((slot-name (getf pl :name))
                                       (acc-name
                                        (format nil
                                                "~S structure class ~A"
                                                name slot-name))
                                       (accessor (intern acc-name)))
                                  (setq pl (list* :defstruct-accessor-symbol
                                                  accessor pl))))
                              (make-direct-slotd class pl))
                            direct-slots)))
        (setq direct-slots (slot-value class 'direct-slots)))
    (when defstruct-p
      (let ((include (car (slot-value class 'direct-superclasses))))
        (multiple-value-bind (defstruct-form constructor reader-names writer-names)
            (make-structure-class-defstruct-form name direct-slots include)
          (unless (structure-type-p name) (eval defstruct-form))
          (mapc (lambda (dslotd reader-name writer-name)
                  (let* ((reader (gdefinition reader-name))
                         (writer (when (gboundp writer-name)
                                   (gdefinition writer-name))))
                    (setf (slot-value dslotd 'internal-reader-function)
                          reader)
                    (setf (slot-value dslotd 'internal-writer-function)
                          writer)))
                direct-slots reader-names writer-names)
          (setf (slot-value class 'defstruct-form) defstruct-form)
          (setf (slot-value class 'defstruct-constructor) constructor))))
    (add-direct-subclasses class direct-superclasses)
    (setf (slot-value class 'class-precedence-list)
            (compute-class-precedence-list class))
    (setf (slot-value class 'slots) (compute-slots class))
    (let ((lclass (cl:find-class (class-name class))))
      (setf (sb-kernel:class-pcl-class lclass) class)
      (setf (slot-value class 'wrapper) (sb-kernel:class-layout lclass)))
    (update-pv-table-cache-info class)
    (setq predicate-name (if predicate-name-p
                           (setf (slot-value class 'predicate-name)
                                   (car predicate-name))
                           (or (slot-value class 'predicate-name)
                               (setf (slot-value class 'predicate-name)
                                       (make-class-predicate-name
                                        (class-name class))))))
    (make-class-predicate class predicate-name)
    (add-slot-accessors class direct-slots)))
  
(defmethod direct-slot-definition-class ((class structure-class) initargs)
  (declare (ignore initargs))
  (find-class 'structure-direct-slot-definition))

(defmethod finalize-inheritance ((class structure-class))
  nil) ; always finalized
\f
(defun add-slot-accessors (class dslotds)
  (fix-slot-accessors class dslotds 'add))

(defun remove-slot-accessors (class dslotds)
  (fix-slot-accessors class dslotds 'remove))

(defun fix-slot-accessors (class dslotds add/remove)
  (flet ((fix (gfspec name r/w)
           (let ((gf (ensure-generic-function gfspec)))
             (case r/w
               (r (if (eq add/remove 'add)
                      (add-reader-method class gf name)
                      (remove-reader-method class gf)))
               (w (if (eq add/remove 'add)
                      (add-writer-method class gf name)
                      (remove-writer-method class gf)))))))
    (dolist (dslotd dslotds)
      (let ((slot-name (slot-definition-name dslotd)))
        (dolist (r (slot-definition-readers dslotd)) (fix r slot-name 'r))
        (dolist (w (slot-definition-writers dslotd)) (fix w slot-name 'w))))))
\f
(defun add-direct-subclasses (class supers)
  (dolist (super supers)
    (unless (memq class (class-direct-subclasses class))
      (add-direct-subclass super class))))

(defun remove-direct-subclasses (class supers)
  (let ((old (class-direct-superclasses class)))
    (dolist (o (set-difference old supers))
      (remove-direct-subclass o class))))
\f
(defmethod finalize-inheritance ((class std-class))
  (update-class class t))
\f
(defun class-has-a-forward-referenced-superclass-p (class)
  (or (forward-referenced-class-p class)
      (some #'class-has-a-forward-referenced-superclass-p
            (class-direct-superclasses class))))

;;; This is called by :after shared-initialize whenever a class is initialized
;;; or reinitialized. The class may or may not be finalized.
(defun update-class (class finalizep)
  ;; Comment from Gerd Moellmann:
  ;;
  ;; Note that we can't simply delay the finalization when CLASS has
  ;; no forward referenced superclasses because that causes bootstrap
  ;; problems.
  (when (and (not finalizep)
             (not (class-finalized-p class))
             (not (class-has-a-forward-referenced-superclass-p class)))
    (finalize-inheritance class)
    (return-from update-class))
  (when (or finalizep (class-finalized-p class)
            (not (class-has-a-forward-referenced-superclass-p class)))
    (update-cpl class (compute-class-precedence-list class))
    ;; This invocation of UPDATE-SLOTS, in practice, finalizes the
    ;; class.  The hoops above are to ensure that FINALIZE-INHERITANCE
    ;; is called at finalization, so that MOP programmers can hook
    ;; into the system as described in "Class Finalization Protocol"
    ;; (section 5.5.2 of AMOP).
    (update-slots class (compute-slots class))
    (update-gfs-of-class class)
    (update-inits class (compute-default-initargs class))
    (update-make-instance-function-table class))
  (unless finalizep
    (dolist (sub (class-direct-subclasses class)) (update-class sub nil))))

(defun update-cpl (class cpl)
  (if (class-finalized-p class)
      (unless (equal (class-precedence-list class) cpl)
        ;; comment from the old CMU CL sources:
        ;;   Need to have the cpl setup before update-lisp-class-layout
        ;;   is called on CMU CL.
        (setf (slot-value class 'class-precedence-list) cpl)
        (force-cache-flushes class))
      (setf (slot-value class 'class-precedence-list) cpl))
  (update-class-can-precede-p cpl))

(defun update-class-can-precede-p (cpl)
  (when cpl
    (let ((first (car cpl)))
      (dolist (c (cdr cpl))
        (pushnew c (slot-value first 'can-precede-list))))
    (update-class-can-precede-p (cdr cpl))))

(defun class-can-precede-p (class1 class2)
  (member class2 (class-can-precede-list class1)))

(defun update-slots (class eslotds)
  (let ((instance-slots ())
        (class-slots    ()))
    (dolist (eslotd eslotds)
      (let ((alloc (slot-definition-allocation eslotd)))
        (case alloc
          (:instance (push eslotd instance-slots))
          (:class (push eslotd class-slots)))))

    ;; If there is a change in the shape of the instances then the
    ;; old class is now obsolete.
    (let* ((nlayout (mapcar #'slot-definition-name
                            (sort instance-slots #'<
                                  :key #'slot-definition-location)))
           (nslots (length nlayout))
           (nwrapper-class-slots (compute-class-slots class-slots))
           (owrapper (class-wrapper class))
           (olayout (and owrapper (wrapper-instance-slots-layout owrapper)))
           (owrapper-class-slots (and owrapper (wrapper-class-slots owrapper)))
           (nwrapper
            (cond ((null owrapper)
                   (make-wrapper nslots class))
                  ((and (equal nlayout olayout)
                        (not
                         (loop for o in owrapper-class-slots
                               for n in nwrapper-class-slots
                               do (unless (eq (car o) (car n)) (return t)))))
                   owrapper)
                  (t
                   ;; This will initialize the new wrapper to have the
                   ;; same state as the old wrapper. We will then have
                   ;; to change that. This may seem like wasted work
                   ;; (and it is), but the spec requires that we call
                   ;; MAKE-INSTANCES-OBSOLETE.
                   (make-instances-obsolete class)
                   (class-wrapper class)))))

      (with-slots (wrapper slots) class
        (update-lisp-class-layout class nwrapper)
        (setf slots eslotds
              (wrapper-instance-slots-layout nwrapper) nlayout
              (wrapper-class-slots nwrapper) nwrapper-class-slots
              (wrapper-no-of-instance-slots nwrapper) nslots
              wrapper nwrapper))

      (unless (eq owrapper nwrapper)
        (update-pv-table-cache-info class)))))

(defun compute-class-slots (eslotds)
  (let (collect)
    (dolist (eslotd eslotds)
      (push (assoc (slot-definition-name eslotd)
                   (class-slot-cells (slot-definition-class eslotd)))
            collect))
    (nreverse collect)))

(defun compute-layout (cpl instance-eslotds)
  (let* ((names
           (let (collect)
             (dolist (eslotd instance-eslotds)
               (when (eq (slot-definition-allocation eslotd) :instance)
                 (push (slot-definition-name eslotd) collect)))
             (nreverse collect)))
         (order ()))
    (labels ((rwalk (tail)
               (when tail
                 (rwalk (cdr tail))
                 (dolist (ss (class-slots (car tail)))
                   (let ((n (slot-definition-name ss)))
                     (when (member n names)
                       (setq order (cons n order)
                             names (remove n names))))))))
      (rwalk (if (slot-boundp (car cpl) 'slots)
                 cpl
                 (cdr cpl)))
      (reverse (append names order)))))

(defun update-gfs-of-class (class)
  (when (and (class-finalized-p class)
             (let ((cpl (class-precedence-list class)))
               (or (member *the-class-slot-class* cpl)
                   (member *the-class-standard-effective-slot-definition*
                           cpl))))
    (let ((gf-table (make-hash-table :test 'eq)))
      (labels ((collect-gfs (class)
                 (dolist (gf (specializer-direct-generic-functions class))
                   (setf (gethash gf gf-table) t))
                 (mapc #'collect-gfs (class-direct-superclasses class))))
        (collect-gfs class)
        (maphash (lambda (gf ignore)
                   (declare (ignore ignore))
                   (update-gf-dfun class gf))
                 gf-table)))))

(defun update-inits (class inits)
  (setf (plist-value class 'default-initargs) inits))
\f
(defmethod compute-default-initargs ((class slot-class))
  (let ((cpl (class-precedence-list class))
        (direct (class-direct-default-initargs class)))
    (labels ((walk (tail)
               (if (null tail)
                   nil
                   (let ((c (pop tail)))
                     (append (if (eq c class)
                                 direct
                                 (class-direct-default-initargs c))
                             (walk tail))))))
      (let ((initargs (walk cpl)))
        (delete-duplicates initargs :test #'eq :key #'car :from-end t)))))
\f
;;;; protocols for constructing direct and effective slot definitions

(defmethod direct-slot-definition-class ((class std-class) initargs)
  (declare (ignore initargs))
  (find-class 'standard-direct-slot-definition))

(defun make-direct-slotd (class initargs)
  (let ((initargs (list* :class class initargs)))
    (apply #'make-instance
           (direct-slot-definition-class class initargs)
           initargs)))

(defmethod compute-slots ((class std-class))
  ;; As specified, we must call COMPUTE-EFFECTIVE-SLOT-DEFINITION once
  ;; for each different slot name we find in our superclasses. Each
  ;; call receives the class and a list of the dslotds with that name.
  ;; The list is in most-specific-first order.
  (let ((name-dslotds-alist ()))
    (dolist (c (class-precedence-list class))
      (let ((dslotds (class-direct-slots c)))
        (dolist (d dslotds)
          (let* ((name (slot-definition-name d))
                 (entry (assq name name-dslotds-alist)))
            (if entry
                (push d (cdr entry))
                (push (list name d) name-dslotds-alist))))))
    (mapcar (lambda (direct)
              (compute-effective-slot-definition class
                                                 (nreverse (cdr direct))))
            name-dslotds-alist)))

(defmethod compute-slots :around ((class std-class))
  (let ((eslotds (call-next-method))
        (cpl (class-precedence-list class))
        (instance-slots ())
        (class-slots    ()))
    (dolist (eslotd eslotds)
      (let ((alloc (slot-definition-allocation eslotd)))
        (case alloc
          (:instance (push eslotd instance-slots))
          (:class (push eslotd class-slots)))))
    (let ((nlayout (compute-layout cpl instance-slots)))
      (dolist (eslotd instance-slots)
        (setf (slot-definition-location eslotd)
              (position (slot-definition-name eslotd) nlayout))))
    (dolist (eslotd class-slots)
      (setf (slot-definition-location eslotd)
            (assoc (slot-definition-name eslotd)
                   (class-slot-cells (slot-definition-class eslotd)))))
    (mapc #'initialize-internal-slot-functions eslotds)
    eslotds))

(defmethod compute-slots ((class structure-class))
  (mapcan (lambda (superclass)
            (mapcar (lambda (dslotd)
                      (compute-effective-slot-definition class
                                                         (list dslotd)))
                    (class-direct-slots superclass)))
          (reverse (slot-value class 'class-precedence-list))))

(defmethod compute-slots :around ((class structure-class))
  (let ((eslotds (call-next-method)))
    (mapc #'initialize-internal-slot-functions eslotds)
    eslotds))

(defmethod compute-effective-slot-definition ((class slot-class) dslotds)
  (let* ((initargs (compute-effective-slot-definition-initargs class dslotds))
         (class (effective-slot-definition-class class initargs)))
    (apply #'make-instance class initargs)))

(defmethod effective-slot-definition-class ((class std-class) initargs)
  (declare (ignore initargs))
  (find-class 'standard-effective-slot-definition))

(defmethod effective-slot-definition-class ((class structure-class) initargs)
  (declare (ignore initargs))
  (find-class 'structure-effective-slot-definition))

(defmethod compute-effective-slot-definition-initargs
    ((class slot-class) direct-slotds)
  (let* ((name nil)
         (initfunction nil)
         (initform nil)
         (initargs nil)
         (allocation nil)
         (type t)
         (namep  nil)
         (initp  nil)
         (allocp nil))

    (dolist (slotd direct-slotds)
      (when slotd
        (unless namep
          (setq name (slot-definition-name slotd)
                namep t))
        (unless initp
          (when (slot-definition-initfunction slotd)
            (setq initform (slot-definition-initform slotd)
                  initfunction (slot-definition-initfunction slotd)
                  initp t)))
        (unless allocp
          (setq allocation (slot-definition-allocation slotd)
                allocp t))
        (setq initargs (append (slot-definition-initargs slotd) initargs))
        (let ((slotd-type (slot-definition-type slotd)))
          (setq type (cond ((eq type t) slotd-type)
                           ((*subtypep type slotd-type) type)
                           (t `(and ,type ,slotd-type)))))))
    (list :name name
          :initform initform
          :initfunction initfunction
          :initargs initargs
          :allocation allocation
          :type type
          :class class)))

(defmethod compute-effective-slot-definition-initargs :around
    ((class structure-class) direct-slotds)
  (let ((slotd (car direct-slotds)))
    (list* :defstruct-accessor-symbol
           (slot-definition-defstruct-accessor-symbol slotd)
           :internal-reader-function
           (slot-definition-internal-reader-function slotd)
           :internal-writer-function
           (slot-definition-internal-writer-function slotd)
           (call-next-method))))
\f
;;; NOTE: For bootstrapping considerations, these can't use MAKE-INSTANCE
;;;       to make the method object. They have to use make-a-method which
;;;       is a specially bootstrapped mechanism for making standard methods.
(defmethod reader-method-class ((class slot-class) direct-slot &rest initargs)
  (declare (ignore direct-slot initargs))
  (find-class 'standard-reader-method))

(defmethod add-reader-method ((class slot-class) generic-function slot-name)
  (add-method generic-function
              (make-a-method 'standard-reader-method
                             ()
                             (list (or (class-name class) 'object))
                             (list class)
                             (make-reader-method-function class slot-name)
                             "automatically generated reader method"
                             slot-name)))

(defmethod writer-method-class ((class slot-class) direct-slot &rest initargs)
  (declare (ignore direct-slot initargs))
  (find-class 'standard-writer-method))

(defmethod add-writer-method ((class slot-class) generic-function slot-name)
  (add-method generic-function
              (make-a-method 'standard-writer-method
                             ()
                             (list 'new-value (or (class-name class) 'object))
                             (list *the-class-t* class)
                             (make-writer-method-function class slot-name)
                             "automatically generated writer method"
                             slot-name)))

(defmethod add-boundp-method ((class slot-class) generic-function slot-name)
  (add-method generic-function
              (make-a-method 'standard-boundp-method
                             ()
                             (list (or (class-name class) 'object))
                             (list class)
                             (make-boundp-method-function class slot-name)
                             "automatically generated boundp method"
                             slot-name)))

(defmethod remove-reader-method ((class slot-class) generic-function)
  (let ((method (get-method generic-function () (list class) nil)))
    (when method (remove-method generic-function method))))

(defmethod remove-writer-method ((class slot-class) generic-function)
  (let ((method
          (get-method generic-function () (list *the-class-t* class) nil)))
    (when method (remove-method generic-function method))))

(defmethod remove-boundp-method ((class slot-class) generic-function)
  (let ((method (get-method generic-function () (list class) nil)))
    (when method (remove-method generic-function method))))
\f
;;; MAKE-READER-METHOD-FUNCTION and MAKE-WRITE-METHOD function are NOT
;;; part of the standard protocol. They are however useful, PCL makes
;;; use of them internally and documents them for PCL users.
;;;
;;; *** This needs work to make type testing by the writer functions which
;;; *** do type testing faster. The idea would be to have one constructor
;;; *** for each possible type test.
;;;
;;; *** There is a subtle bug here which is going to have to be fixed.
;;; *** Namely, the simplistic use of the template has to be fixed. We
;;; *** have to give the OPTIMIZE-SLOT-VALUE method the user might have
;;; *** defined for this metaclass a chance to run.

(defmethod make-reader-method-function ((class slot-class) slot-name)
  (make-std-reader-method-function (class-name class) slot-name))

(defmethod make-writer-method-function ((class slot-class) slot-name)
  (make-std-writer-method-function (class-name class) slot-name))

(defmethod make-boundp-method-function ((class slot-class) slot-name)
  (make-std-boundp-method-function (class-name class) slot-name))
\f
(defmethod compatible-meta-class-change-p (class proto-new-class)
  (eq (class-of class) (class-of proto-new-class)))

(defmethod validate-superclass ((class class) (new-super class))
  (or (eq new-super *the-class-t*)
      (eq (class-of class) (class-of new-super))))

(defmethod validate-superclass ((class standard-class) (new-super std-class))
  (let ((new-super-meta-class (class-of new-super)))
    (or (eq new-super-meta-class *the-class-std-class*)
        (eq (class-of class) new-super-meta-class))))
\f
(defun force-cache-flushes (class)
  (let* ((owrapper (class-wrapper class)))
    ;; We only need to do something if the state is still T. If the
    ;; state isn't T, it will be FLUSH or OBSOLETE, and both of those
    ;; will already be doing what we want. In particular, we must be
    ;; sure we never change an OBSOLETE into a FLUSH since OBSOLETE
    ;; means do what FLUSH does and then some.
    (unless (invalid-wrapper-p owrapper)
      (let ((nwrapper (make-wrapper (wrapper-no-of-instance-slots owrapper)
                                    class)))
        (setf (wrapper-instance-slots-layout nwrapper)
              (wrapper-instance-slots-layout owrapper))
        (setf (wrapper-class-slots nwrapper)
              (wrapper-class-slots owrapper))
        (sb-sys:without-interrupts
          (update-lisp-class-layout class nwrapper)
          (setf (slot-value class 'wrapper) nwrapper)
          (invalidate-wrapper owrapper :flush nwrapper))))))

(defun flush-cache-trap (owrapper nwrapper instance)
  (declare (ignore owrapper))
  (set-wrapper instance nwrapper))
\f
;;; MAKE-INSTANCES-OBSOLETE can be called by user code. It will cause
;;; the next access to the instance (as defined in 88-002R) to trap
;;; through the UPDATE-INSTANCE-FOR-REDEFINED-CLASS mechanism.
(defmethod make-instances-obsolete ((class std-class))
  (let* ((owrapper (class-wrapper class))
         (nwrapper (make-wrapper (wrapper-no-of-instance-slots owrapper)
                                 class)))
      (setf (wrapper-instance-slots-layout nwrapper)
            (wrapper-instance-slots-layout owrapper))
      (setf (wrapper-class-slots nwrapper)
            (wrapper-class-slots owrapper))
      (sb-sys:without-interrupts
        (update-lisp-class-layout class nwrapper)
        (setf (slot-value class 'wrapper) nwrapper)
        (invalidate-wrapper owrapper :obsolete nwrapper)
        class)))

(defmethod make-instances-obsolete ((class symbol))
  (make-instances-obsolete (find-class class)))

;;; OBSOLETE-INSTANCE-TRAP is the internal trap that is called when we
;;; see an obsolete instance. The times when it is called are:
;;;   - when the instance is involved in method lookup
;;;   - when attempting to access a slot of an instance
;;;
;;; It is not called by class-of, wrapper-of, or any of the low-level
;;; instance access macros.
;;;
;;; Of course these times when it is called are an internal
;;; implementation detail of PCL and are not part of the documented
;;; description of when the obsolete instance update happens. The
;;; documented description is as it appears in 88-002R.
;;;
;;; This has to return the new wrapper, so it counts on all the
;;; methods on obsolete-instance-trap-internal to return the new
;;; wrapper. It also does a little internal error checking to make
;;; sure that the traps are only happening when they should, and that
;;; the trap methods are computing appropriate new wrappers.

;;; OBSOLETE-INSTANCE-TRAP might be called on structure instances
;;; after a structure is redefined. In most cases,
;;; OBSOLETE-INSTANCE-TRAP will not be able to fix the old instance,
;;; so it must signal an error. The hard part of this is that the
;;; error system and debugger might cause OBSOLETE-INSTANCE-TRAP to be
;;; called again, so in that case, we have to return some reasonable
;;; wrapper, instead.

(defvar *in-obsolete-instance-trap* nil)
(defvar *the-wrapper-of-structure-object*
  (class-wrapper (find-class 'structure-object)))

(define-condition obsolete-structure (error)
  ((datum :reader obsolete-structure-datum :initarg :datum))
  (:report
   (lambda (condition stream)
     ;; Don't try to print the structure, since it probably won't work.
     (format stream
             "~@<obsolete structure error for a structure of type ~2I~_~S~:>"
             (type-of (obsolete-structure-datum condition))))))

(defun obsolete-instance-trap (owrapper nwrapper instance)
  (if (not (pcl-instance-p instance))
      (if *in-obsolete-instance-trap*
          *the-wrapper-of-structure-object*
           (let ((*in-obsolete-instance-trap* t))
             (error 'obsolete-structure :datum instance)))
      (let* ((class (wrapper-class* nwrapper))
             (copy (allocate-instance class)) ;??? allocate-instance ???
             (olayout (wrapper-instance-slots-layout owrapper))
             (nlayout (wrapper-instance-slots-layout nwrapper))
             (oslots (get-slots instance))
             (nslots (get-slots copy))
             (oclass-slots (wrapper-class-slots owrapper))
             (added ())
             (discarded ())
             (plist ()))
        ;; local  --> local     transfer
        ;; local  --> shared       discard
        ;; local  -->  --         discard
        ;; shared --> local     transfer
        ;; shared --> shared       discard
        ;; shared -->  --         discard
        ;;  --    --> local     add
        ;;  --    --> shared    --

        ;; Go through all the old local slots.
        (let ((opos 0))
          (dolist (name olayout)
            (let ((npos (posq name nlayout)))
              (if npos
                  (setf (clos-slots-ref nslots npos)
                        (clos-slots-ref oslots opos))
                  (progn
                    (push name discarded)
                    (unless (eq (clos-slots-ref oslots opos) +slot-unbound+)
                      (setf (getf plist name) (clos-slots-ref oslots opos))))))
            (incf opos)))

        ;; Go through all the old shared slots.
        (dolist (oclass-slot-and-val oclass-slots)
          (let ((name (car oclass-slot-and-val))
                (val (cdr oclass-slot-and-val)))
            (let ((npos (posq name nlayout)))
              (if npos
                  (setf (clos-slots-ref nslots npos) (cdr oclass-slot-and-val))
                  (progn (push name discarded)
                         (unless (eq val +slot-unbound+)
                           (setf (getf plist name) val)))))))

        ;; Go through all the new local slots to compute the added slots.
        (dolist (nlocal nlayout)
          (unless (or (memq nlocal olayout)
                      (assq nlocal oclass-slots))
            (push nlocal added)))

        (swap-wrappers-and-slots instance copy)

        (update-instance-for-redefined-class instance
                                             added
                                             discarded
                                             plist)
        nwrapper)))
\f
(defun change-class-internal (instance new-class initargs)
  (let* ((old-class (class-of instance))
         (copy (allocate-instance new-class))
         (new-wrapper (get-wrapper copy))
         (old-wrapper (class-wrapper old-class))
         (old-layout (wrapper-instance-slots-layout old-wrapper))
         (new-layout (wrapper-instance-slots-layout new-wrapper))
         (old-slots (get-slots instance))
         (new-slots (get-slots copy))
         (old-class-slots (wrapper-class-slots old-wrapper)))

    ;; "The values of local slots specified by both the class CTO and
    ;; CFROM are retained. If such a local slot was unbound, it
    ;; remains unbound."
    (let ((new-position 0))
      (dolist (new-slot new-layout)
        (let ((old-position (posq new-slot old-layout)))
          (when old-position
            (setf (clos-slots-ref new-slots new-position)
                  (clos-slots-ref old-slots old-position))))
        (incf new-position)))

    ;; "The values of slots specified as shared in the class CFROM and
    ;; as local in the class CTO are retained."
    (dolist (slot-and-val old-class-slots)
      (let ((position (posq (car slot-and-val) new-layout)))
        (when position
          (setf (clos-slots-ref new-slots position) (cdr slot-and-val)))))

    ;; Make the copy point to the old instance's storage, and make the
    ;; old instance point to the new storage.
    (swap-wrappers-and-slots instance copy)

    (apply #'update-instance-for-different-class copy instance initargs)
    instance))

(defmethod change-class ((instance standard-object)
                         (new-class standard-class)
                         &rest initargs)
  (change-class-internal instance new-class initargs))

(defmethod change-class ((instance funcallable-standard-object)
                         (new-class funcallable-standard-class)
                         &rest initargs)
  (change-class-internal instance new-class initargs))

(defmethod change-class ((instance standard-object)
                         (new-class funcallable-standard-class)
                         &rest initargs)
  (declare (ignore initargs))
  (error "You can't change the class of ~S to ~S~@
          because it isn't already an instance with metaclass ~S."
         instance new-class 'standard-class))

(defmethod change-class ((instance funcallable-standard-object)
                         (new-class standard-class)
                         &rest initargs)
  (declare (ignore initargs))
  (error "You can't change the class of ~S to ~S~@
          because it isn't already an instance with metaclass ~S."
         instance new-class 'funcallable-standard-class))

(defmethod change-class ((instance t) (new-class-name symbol) &rest initargs)
  (apply #'change-class instance (find-class new-class-name) initargs))
\f
;;;; The metaclass BUILT-IN-CLASS
;;;;
;;;; This metaclass is something of a weird creature. By this point, all
;;;; instances of it which will exist have been created, and no instance
;;;; is ever created by calling MAKE-INSTANCE.
;;;;
;;;; But, there are other parts of the protocol we must follow and those
;;;; definitions appear here.

(defmethod shared-initialize :before
           ((class built-in-class) slot-names &rest initargs)
  (declare (ignore slot-names initargs))
  (error "attempt to initialize or reinitialize a built in class"))

(defmethod class-direct-slots       ((class built-in-class)) ())
(defmethod class-slots             ((class built-in-class)) ())
(defmethod class-direct-default-initargs ((class built-in-class)) ())
(defmethod class-default-initargs       ((class built-in-class)) ())

(defmethod validate-superclass ((c class) (s built-in-class))
  (or (eq s *the-class-t*)
      (eq s *the-class-stream*)))
\f
(defmethod validate-superclass ((c slot-class)
                                (f forward-referenced-class))
  t)
\f
(defmethod add-dependent ((metaobject dependent-update-mixin) dependent)
  (pushnew dependent (plist-value metaobject 'dependents)))

(defmethod remove-dependent ((metaobject dependent-update-mixin) dependent)
  (setf (plist-value metaobject 'dependents)
        (delete dependent (plist-value metaobject 'dependents))))

(defmethod map-dependents ((metaobject dependent-update-mixin) function)
  (dolist (dependent (plist-value metaobject 'dependents))
    (funcall function dependent)))