defclass.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")


(defun make-progn (&rest forms)
  (let ((progn-form nil))
    (labels ((collect-forms (forms)
	       (unless (null forms)
		 (collect-forms (cdr forms))
		 (if (and (listp (car forms))
			  (eq (caar forms) 'progn))
		     (collect-forms (cdar forms))
		     (push (car forms) progn-form)))))
      (collect-forms forms)
      (cons 'progn progn-form))))

;;; Like the DEFMETHOD macro, the expansion of the DEFCLASS macro is
;;; fixed. DEFCLASS always expands into a call to LOAD-DEFCLASS. Until
;;; the meta-braid is set up, LOAD-DEFCLASS has a special definition
;;; which simply collects all class definitions up, when the metabraid
;;; is initialized it is done from those class definitions.
;;;
;;; After the metabraid has been setup, and the protocol for defining
;;; classes has been defined, the real definition of LOAD-DEFCLASS is
;;; installed by the file defclass.lisp
(defmacro defclass (name direct-superclasses direct-slots &rest options)
  (expand-defclass name direct-superclasses direct-slots options))

(defun expand-defclass (name supers slots options)
  (setq supers  (copy-tree supers)
	slots   (copy-tree slots)
	options (copy-tree options))
  (let ((metaclass 'standard-class))
    (dolist (option options)
      (if (not (listp option))
	  (error "~S is not a legal defclass option." option)
	  (when (eq (car option) ':metaclass)
	    (unless (legal-class-name-p (cadr option))
	      (error "The value of the :metaclass option (~S) is not a~%~
		      legal class name."
		     (cadr option)))
	    (setq metaclass
		  (case (cadr option)
		    (cl:standard-class 'standard-class)
		    (cl:structure-class 'structure-class)
		    (t (cadr option))))
	    (setf options (remove option options))
	    (return t))))

    (let ((*initfunctions* ())
	  (*readers* ())		;Truly a crock, but we got
	  (*writers* ()))               ;to have it to live nicely.
      (declare (special *initfunctions* *readers* *writers*))
      (let ((canonical-slots
	      (mapcar #'(lambda (spec)
			  (canonicalize-slot-specification name spec))
		      slots))
	    (other-initargs
	      (mapcar #'(lambda (option)
			  (canonicalize-defclass-option name option))
		      options))
	    (defstruct-p (and (eq *boot-state* 'complete)
			      (let ((mclass (find-class metaclass nil)))
				(and mclass
				     (*subtypep
				      mclass
				      *the-class-structure-class*))))))
	(let ((defclass-form
		`(progn
		   ,@(mapcar (lambda (x)
			       `(declaim (ftype (function (t) t) ,x)))
			     *readers*)
		   ,@(mapcar (lambda (x)
			       `(declaim (ftype (function (t t) t) ,x)))
			     *writers*)
		   (let ,(mapcar #'cdr *initfunctions*)
		     (load-defclass ',name
				    ',metaclass
				    ',supers
				    (list ,@canonical-slots)
				    (list ,@(apply #'append
						   (when defstruct-p
						     '(:from-defclass-p t))
						   other-initargs)))))))
	  ;; FIXME: The way that we do things like (EVAL DEFCLASS-FORM)
	  ;; here is un-ANSI-Common-Lisp-y and leads to problems
	  ;; (like DEFUN for the type predicate being called more than
	  ;; once when we do DEFCLASS at the interpreter prompt),
	  ;; causing bogus style warnings. It would be better to
	  ;; rewrite this so that the macroexpansion looks like e.g.
	  ;; (PROGN
	  ;;   (EVAL-WHEN (:COMPILE-TOPLEVEL :LOAD-TOPLEVEL :EXECUTE)
	  ;;     (FROB1 ..))
	  ;;   (EVAL-WHEN (:LOAD-TOPLEVEL :EXECUTE)
	  ;;     (FROB2 ..)))
	  (if defstruct-p
	      (progn
		(eval defclass-form) ; Define the class now, so that..
		`(progn	      ; ..the defstruct can be compiled.
		   ,(class-defstruct-form (find-class name))
		   ,defclass-form))
	      (progn
		(when (eq *boot-state* 'complete)
		  ;; FIXME: MNA (on sbcl-devel 2001-05-30) reported
		  ;; (if I understand correctly -- WHN) that this call
		  ;; is directly responsible for defining
		  ;; class-predicates which always return
		  ;; CONSTANTLY-NIL in the compile-time environment,
		  ;; and is indirectly responsible for bogus warnings
		  ;; about redefinitions when making definitions in
		  ;; the interpreter. I didn't like his fix (deleting
		  ;; the call) since I think the type system *should*
		  ;; be informed about class definitions here. And I'm
		  ;; not eager to look too deeply into this sort of
		  ;; done-too-many-times-in-the-interpreter problem
		  ;; right now, since it should be easier to make a
		  ;; clean fix when EVAL-WHEN is made more ANSI (as
		  ;; per the IR1 section in the BUGS file). But
		  ;; at some point this should be cleaned up.
		  (inform-type-system-about-std-class name))
		defclass-form)))))))

(defun make-initfunction (initform)
  (declare (special *initfunctions*))
  (cond ((or (eq initform t)
	     (equal initform ''t))
	 '(function constantly-t))
	((or (eq initform nil)
	     (equal initform ''nil))
	 '(function constantly-nil))
	((or (eql initform 0)
	     (equal initform ''0))
	 '(function constantly-0))
	(t
	 (let ((entry (assoc initform *initfunctions* :test #'equal)))
	   (unless entry
	     (setq entry (list initform
			       (gensym)
			       `(function (lambda () ,initform))))
	     (push entry *initfunctions*))
	   (cadr entry)))))

(defun canonicalize-slot-specification (class-name spec)
  (declare (special *readers* *writers*))
  (cond ((and (symbolp spec)
	      (not (keywordp spec))
	      (not (memq spec '(t nil))))
	 `'(:name ,spec))
	((not (consp spec))
	 (error "~S is not a legal slot specification." spec))
	((null (cdr spec))
	 `'(:name ,(car spec)))
	((null (cddr spec))
	 (error "In DEFCLASS ~S, the slot specification ~S is obsolete.~%~
		 Convert it to ~S"
		class-name spec (list (car spec) :initform (cadr spec))))
	(t
	 (let* ((name (pop spec))
		(readers ())
		(writers ())
		(initargs ())
		(unsupplied (list nil))
		(initform (getf spec :initform unsupplied)))
	   (doplist (key val) spec
	     (case key
	       (:accessor (push val readers)
			  (push `(setf ,val) writers))
	       (:reader   (push val readers))
	       (:writer   (push val writers))
	       (:initarg  (push val initargs))))
	   (loop (unless (remf spec :accessor) (return)))
	   (loop (unless (remf spec :reader)   (return)))
	   (loop (unless (remf spec :writer)   (return)))
	   (loop (unless (remf spec :initarg)  (return)))
	   (setq *writers* (append writers *writers*))
	   (setq *readers* (append readers *readers*))
	   (setq spec `(:name     ',name
			:readers  ',readers
			:writers  ',writers
			:initargs ',initargs
			',spec))
	   (if (eq initform unsupplied)
	       `(list* ,@spec)
	       `(list* :initfunction ,(make-initfunction initform) ,@spec))))))
						
(defun canonicalize-defclass-option (class-name option)
  (declare (ignore class-name))
  (case (car option)
    (:default-initargs
      (let ((canonical ()))
	(let (key val (tail (cdr option)))
	  (loop (when (null tail) (return nil))
		(setq key (pop tail)
		      val (pop tail))
		(push ``(,',key ,,(make-initfunction val) ,',val) canonical))
	  `(':direct-default-initargs (list ,@(nreverse canonical))))))
    (:documentation
      `(',(car option) ',(cadr option)))
    (otherwise
     `(',(car option) ',(cdr option)))))

;;; This is the early definition of load-defclass. It just collects up
;;; all the class definitions in a list. Later, in the file
;;; braid1.lisp, these are actually defined.

;;; Each entry in *EARLY-CLASS-DEFINITIONS* is an EARLY-CLASS-DEFINITION.
(defparameter *early-class-definitions* ())

(defun early-class-definition (class-name)
  (or (find class-name *early-class-definitions* :key #'ecd-class-name)
      (error "~S is not a class in *early-class-definitions*." class-name)))

(defun make-early-class-definition
       (name source metaclass
	superclass-names canonical-slots other-initargs)
  (list 'early-class-definition
	name source metaclass
	superclass-names canonical-slots other-initargs))

(defun ecd-class-name        (ecd) (nth 1 ecd))
(defun ecd-source            (ecd) (nth 2 ecd))
(defun ecd-metaclass         (ecd) (nth 3 ecd))
(defun ecd-superclass-names  (ecd) (nth 4 ecd))
(defun ecd-canonical-slots   (ecd) (nth 5 ecd))
(defun ecd-other-initargs    (ecd) (nth 6 ecd))

(defvar *early-class-slots* nil)

(defun canonical-slot-name (canonical-slot)
  (getf canonical-slot :name))

(defun early-class-slots (class-name)
  (cdr (or (assoc class-name *early-class-slots*)
	   (let ((a (cons class-name
			  (mapcar #'canonical-slot-name
				  (early-collect-inheritance class-name)))))
	     (push a *early-class-slots*)
	     a))))

(defun early-class-size (class-name)
  (length (early-class-slots class-name)))

(defun early-collect-inheritance (class-name)
  ;;(declare (values slots cpl default-initargs direct-subclasses))
  (let ((cpl (early-collect-cpl class-name)))
    (values (early-collect-slots cpl)
	    cpl
	    (early-collect-default-initargs cpl)
	    (gathering1 (collecting)
	      (dolist (definition *early-class-definitions*)
		(when (memq class-name (ecd-superclass-names definition))
		  (gather1 (ecd-class-name definition))))))))

(defun early-collect-slots (cpl)
  (let* ((definitions (mapcar #'early-class-definition cpl))
	 (super-slots (mapcar #'ecd-canonical-slots definitions))
	 (slots (apply #'append (reverse super-slots))))
    (dolist (s1 slots)
      (let ((name1 (canonical-slot-name s1)))
	(dolist (s2 (cdr (memq s1 slots)))
	  (when (eq name1 (canonical-slot-name s2))
	    (error "More than one early class defines a slot with the~%~
		    name ~S. This can't work because the bootstrap~%~
		    object system doesn't know how to compute effective~%~
		    slots."
		   name1)))))
    slots))

(defun early-collect-cpl (class-name)
  (labels ((walk (c)
	     (let* ((definition (early-class-definition c))
		    (supers (ecd-superclass-names definition)))
	       (cons c
		     (apply #'append (mapcar #'early-collect-cpl supers))))))
    (remove-duplicates (walk class-name) :from-end nil :test #'eq)))

(defun early-collect-default-initargs (cpl)
  (let ((default-initargs ()))
    (dolist (class-name cpl)
      (let* ((definition (early-class-definition class-name))
	     (others (ecd-other-initargs definition)))
	(loop (when (null others) (return nil))
	      (let ((initarg (pop others)))
		(unless (eq initarg :direct-default-initargs)
		 (error "~@<The defclass option ~S is not supported by ~
			the bootstrap object system.~:@>"
			initarg)))
	      (setq default-initargs
		    (nconc default-initargs (reverse (pop others)))))))
    (reverse default-initargs)))

(defun !bootstrap-slot-index (class-name slot-name)
  (or (position slot-name (early-class-slots class-name))
      (error "~S not found" slot-name)))

;;; !BOOTSTRAP-GET-SLOT and !BOOTSTRAP-SET-SLOT are used to access and
;;; change the values of slots during bootstrapping. During
;;; bootstrapping, there are only two kinds of objects whose slots we
;;; need to access, CLASSes and SLOT-DEFINITIONs. The first argument
;;; to these functions tells whether the object is a CLASS or a
;;; SLOT-DEFINITION.
;;;
;;; Note that the way this works it stores the slot in the same place
;;; in memory that the full object system will expect to find it
;;; later. This is critical to the bootstrapping process, the whole
;;; changeover to the full object system is predicated on this.
;;;
;;; One important point is that the layout of standard classes and
;;; standard slots must be computed the same way in this file as it is
;;; by the full object system later.
(defmacro !bootstrap-get-slot (type object slot-name)
  `(clos-slots-ref (get-slots ,object)
		   (!bootstrap-slot-index ,type ,slot-name)))
(defun !bootstrap-set-slot (type object slot-name new-value)
  (setf (!bootstrap-get-slot type object slot-name) new-value))

(defun early-class-name (class)
  (!bootstrap-get-slot 'class class 'name))

(defun early-class-precedence-list (class)
  (!bootstrap-get-slot 'pcl-class class 'class-precedence-list))

(defun early-class-name-of (instance)
  (early-class-name (class-of instance)))

(defun early-class-slotds (class)
  (!bootstrap-get-slot 'slot-class class 'slots))

(defun early-slot-definition-name (slotd)
  (!bootstrap-get-slot 'standard-effective-slot-definition slotd 'name))

(defun early-slot-definition-location (slotd)
  (!bootstrap-get-slot 'standard-effective-slot-definition slotd 'location))

(defun early-accessor-method-slot-name (method)
  (!bootstrap-get-slot 'standard-accessor-method method 'slot-name))

(unless (fboundp 'class-name-of)
  (setf (symbol-function 'class-name-of)
	(symbol-function 'early-class-name-of)))
(unintern 'early-class-name-of)

(defun early-class-direct-subclasses (class)
  (!bootstrap-get-slot 'class class 'direct-subclasses))

(declaim (notinline load-defclass))
(defun load-defclass (name metaclass supers canonical-slots canonical-options)
  (setq supers  (copy-tree supers)
	canonical-slots   (copy-tree canonical-slots)
	canonical-options (copy-tree canonical-options))
  (when (eq metaclass 'standard-class)
    (inform-type-system-about-std-class name))
  (let ((ecd
	  (make-early-class-definition name
				       *load-truename*
				       metaclass
				       supers
				       canonical-slots
				       canonical-options))
	(existing
	  (find name *early-class-definitions* :key #'ecd-class-name)))
    (setq *early-class-definitions*
	  (cons ecd (remove existing *early-class-definitions*)))
    ecd))