closer-mop-shared.lisp 34.2 KB
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(in-package :closer-mop)

(defun required-args (lambda-list &optional (collector #'identity))
  (loop for arg in lambda-list
        until (member arg lambda-list-keywords)
        collect (funcall collector arg)))

(defun ensure-finalized (class &optional (errorp t))
  (if (typep class 'class)
    (unless (class-finalized-p class)
      (finalize-inheritance class))
    (when errorp (error "~S is not a class." class)))
  class)

(defun subclassp (class superclass)
  (flet ((get-class (class) (etypecase class
                              (class class)
                              (symbol (find-class class)))))
    
      (loop with class = (get-class class)
            with superclass = (get-class superclass)
            
            for superclasses = (list class)
            then (set-difference 
                  (union (class-direct-superclasses current-class) superclasses)
                  seen)

            for current-class = (first superclasses)

            while current-class
            
            if (eq current-class superclass) return t
            else collect current-class into seen
            
            finally (return nil))))

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#+(or allegro clozure ecl lispworks mcl)
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(progn
  ;; validate-superclass for metaclass classes is a little bit
  ;; more tricky than for class metaobject classes because
  ;; we don't want to make all standard-classes compatible to
  ;; each other.
  
  ;; Our validate-superclass may get passed a class-prototype
  ;; as its second argument, so don't expect its readers to
  ;; yield useful information. (In ANSI parlance, "the
  ;; consequences are undefined...")

  (defmacro define-validate-superclass-method (class superclass)
    `(cl:defmethod validate-superclass ((class ,class) (superclass ,superclass))
       (or (when (eq (class-of class) (find-class ',class))
             (or (eq (class-of superclass) (find-class ',superclass))
                 (eq (class-of superclass) (find-class ',class))))
           (call-next-method)
           (when (eq (class-of superclass) (find-class ',superclass))
             (validate-superclass class (class-prototype (find-class ',class))))))))

#+(or clisp scl)
(progn
  (declaim (inline classp))

  (define-compiler-macro classp (thing)
    `(typep ,thing 'class))
  
  (defun classp (thing)
    (typep thing 'class)))

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#+(or allegro clisp clozure ecl lispworks sbcl)
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(progn ;;; New generic functions.

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  #+ecl
  (cl:defgeneric specializer-direct-methods (metaobject))

  #+ecl
  (defclass funcallable-standard-class (clos:funcallable-standard-class)
    ((direct-methods :initform '() :reader specializer-direct-methods)))

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  (defclass standard-generic-function (cl:standard-generic-function)
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    (#+(or clozure ecl lispworks) (argument-order :accessor argument-order)
     #-sbcl                       (initial-methods :initform '())
     #+ecl                        (declarations :initarg :declarations :initform '()
                                                :reader generic-function-declarations))
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    (:metaclass
     #-lispworks funcallable-standard-class
     #+lispworks clos:funcallable-standard-class)
    
    #+clozure
    (:default-initargs :name (gensym) :method-class (find-class 'standard-method)))

  #+clozure
  (progn
    (cl:defgeneric method-function (method)
      (:method ((method method))
       (ccl:method-function method)))

    (defclass standard-method (cl:standard-method)
      ((fn :initarg :real-function :reader method-function))))

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  #-ecl
  (progn
    (declaim (inline m-function))
    
    (defun m-function (m)
      (method-function m))
    
    (define-compiler-macro m-function (m)
      (handler-case (method-function m)
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        (error () `(the function (method-function (the method ,m)))))))
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  (defun compute-argument-order (gf nof-required-args)
    (loop with specialized-count = (make-array nof-required-args :initial-element 0)
        
          for method in (generic-function-methods gf) do
          (loop for specializer in (method-specializers method)
                for index from 0
                unless (eq specializer (find-class 't))
                do (incf (svref specialized-count index)))

          finally
  
          (loop for arg in (generic-function-argument-precedence-order gf)
                for pos = (position arg (generic-function-lambda-list gf))
                when (> (svref specialized-count pos) 0)
                collect pos into argument-order
                finally (return-from compute-argument-order
                          (coerce argument-order 'simple-vector)))))

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  (defun parse-method-body (body error-form)
    (loop with documentation = nil
          for (car . cdr) = body then cdr
          while (or (and cdr (stringp car))
                    (and (consp car) (eq (car car) 'declare)))
          if (stringp car)
          do (setq documentation
                   (if (null documentation) car
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                     (warn "Too many documentation strings in ~S." error-form)))
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          else append (cdr car) into declarations
          finally (return (values documentation declarations (cons car cdr)))))

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  #-sbcl (cl:defgeneric make-method-lambda (generic-function method lambda-expression environment))

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  #-ecl
  (cl:defmethod make-method-lambda ((gf standard-generic-function) (method standard-method)
                                    lambda-expression environment)
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    (declare (ignore environment) (optimize (speed 3) (space 0) (compilation-speed 0)))
    #+(or clozure lispworks sbcl)
    (when (only-standard-methods gf)
      (return-from make-method-lambda (call-next-method)))
    (let ((args (gensym)) (next-methods (gensym))
          (more-args (gensym)) (method-function (gensym)))
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      (destructuring-bind
          (lambda (&rest lambda-args) &body body)
          lambda-expression
        (declare (ignore lambda-args))
        (assert (eq lambda 'lambda))
        (values
         `(lambda (,args ,next-methods &rest ,more-args)
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            (declare (ignorable ,args ,next-methods ,more-args))
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            (flet ((call-next-method (&rest args)
                     (if ,next-methods
                       (apply (method-function (first ,next-methods))
                              (if args args ,args) (rest ,next-methods) ,more-args)
                       (apply #'no-next-method
                              (getf ,more-args :generic-function)
                              (getf ,more-args :method)
                              (if args args ,args))))
                   (next-method-p () (not (null ,next-methods))))
              (declare (inline call-next-method next-method-p)
                       (ignorable #'call-next-method #'next-method-p))
              (flet ((,method-function ,@(rest lambda-expression)))
                (declare (inline ,method-function))
                (apply #',method-function ,args))))
         (let ((documentation (parse-method-body body lambda-expression)))
           (nconc
            (when documentation
              (list :documentation documentation))
            #+clozure '(:closer-patch t)
            #-clozure '()))))))
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  #+(or clozure ecl lispworks)
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  (cl:defgeneric compute-applicable-methods-using-classes (generic-function classes)
    (:method ((gf standard-generic-function) classes)
     (labels ((subclass* (spec1 spec2 arg-spec)
                (let ((cpl (class-precedence-list arg-spec)))
                  (declare (type list cpl))
                  (find spec2 (the list (cdr (member spec1 cpl :test #'eq))) :test #'eq)))
              (method-more-specific-p (m1 m2)
                (declare (type method m1 m2))
                (loop for n of-type fixnum across (argument-order gf)
                      for spec1 = (nth n (method-specializers m1))
                      for spec2 = (nth n (method-specializers m2))
                      unless (eq spec1 spec2)
                      return (subclass* spec1 spec2 (nth n classes)))))
       (let ((applicable-methods
              (sort
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               (loop for method #-ecl of-type #-ecl method in (the list (generic-function-methods gf))
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                     when (loop for class in classes
                                for specializer in (the list (method-specializers method))
                                if (typep specializer 'eql-specializer)
                                do (when (typep (eql-specializer-object specializer) class)
                                     (return-from compute-applicable-methods-using-classes (values '() nil)))
                                else if (not (subclassp class specializer)) return nil
                                finally (return t))
                     collect method)
               #'method-more-specific-p)))
         (values applicable-methods t)))))

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  (cl:defgeneric compute-effective-method-function (gf effective-method options))

  #-ecl
  (cl:defmethod compute-effective-method-function ((gf generic-function) effective-method options)
    (declare (optimize (speed 3) (space 0) (compilation-speed 0)))
    (when #-clisp options
      #+clisp (or (cdr (assoc :arguments options))
                  (cdr (assoc :duplicates options)))
      (cerror "Ignore these options."
              "This version of compute-effective-method-function does not support method combination options: ~S"
              options))
    (let ((all-t-specializers (required-args (generic-function-lambda-list gf)
                                             (constantly (find-class 't))))
          (args (gensym)))
      (labels ((transform-effective-method (form)
                 (if (atom form) form
                   (case (car form)
                     (call-method (transform-effective-method
                                   (let ((the-method (transform-effective-method (cadr form)))
                                         (method-var (gensym)))
                                     `(locally (declare (optimize (speed 3) (safety 0) (debug 0)))
                                        (let ((,method-var ,the-method))
                                          (declare (ignorable ,method-var))
                                          (funcall (m-function ,(if (typep the-method 'method)
                                                                  the-method method-var))
                                                   ,args
                                                   ,@(let ((subforms
                                                            (loop for subform in (the list (cddr form))
                                                                  collect `',subform)))
                                                       (if subforms subforms '(())))
                                                   :generic-function ,gf
                                                   :method ,(if (typep the-method 'method)
                                                              the-method method-var)))))))
                     (make-method (when (cddr form)
                                    (error "Incorrect make-method form: ~S." form))
                                  (let ((method-class (generic-function-method-class gf)))
                                    #+allegro (ensure-finalized method-class)
                                    (multiple-value-bind
                                        (method-lambda method-options)
                                        (make-method-lambda
                                         gf (class-prototype method-class)
                                         `(lambda (&rest ,args)
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                                            (declare (ignorable ,args))
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                                            ,(transform-effective-method (cadr form))) nil)
                                      (apply #'make-instance
                                             method-class
                                             :qualifiers '()
                                             :specializers all-t-specializers
                                             :lambda-list (generic-function-lambda-list gf)
                                             :function (compile nil method-lambda)
                                             method-options))))
                     (t (mapcar #'transform-effective-method (the list form)))))))
        (let ((emf-lambda `(lambda (&rest ,args)
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                             (declare (ignorable ,args))
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                             ,(transform-effective-method effective-method))))
          (multiple-value-bind (function warnings failure)
              (compile nil emf-lambda)
            (declare (ignore warnings))
            (assert (not failure))
            function)))))

  #+clozure
  (cl:defgeneric compute-effective-method (generic-function combination methods))
  
  #+clozure
  (cl:defgeneric compute-discriminating-function (generic-function))

  #+ecl
  (cl:defgeneric compute-effective-method (generic-function combination methods)
    (:method ((gf generic-function) combination methods)
     (clos:compute-effective-method gf combination methods)))

  #+ecl
  (cl:defgeneric compute-applicable-methods (gf arguments)
    (:method ((gf generic-function) arguments)
     (cl:compute-applicable-methods gf arguments)))
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  (defun get-emf (gf args nof-required-args)
    (declare (optimize (speed 3) (space 0) (compilation-speed 0)))
    (let ((applicable-methods (compute-applicable-methods gf (subseq args 0 nof-required-args))))
      (if applicable-methods
        (multiple-value-bind
            (effective-method options)
            (compute-effective-method
             gf (generic-function-method-combination gf)
             applicable-methods)
          (compute-effective-method-function gf effective-method options))
        (lambda (&rest args)
          (apply #'no-applicable-method gf args)))))

  (defun get-emf-using-classes (gf args classes nof-required-args)
    (declare (type generic-function gf) (type list args classes)
             (optimize (speed 3) (space 0) (compilation-speed 0)))
    (multiple-value-bind
        (applicable-methods validp)
        (compute-applicable-methods-using-classes gf classes)
      (unless validp
        (setq applicable-methods
              (compute-applicable-methods gf (subseq args 0 nof-required-args))))
      (values
       (if applicable-methods
         (multiple-value-bind
             (effective-method options)
             (compute-effective-method
              gf (generic-function-method-combination gf)
              applicable-methods)
           (compute-effective-method-function gf effective-method options))
         (lambda (&rest args)
           (apply #'no-applicable-method gf args)))
       validp)))

  (defvar *standard-gfs*
    (list #'compute-applicable-methods #'compute-applicable-methods-using-classes
          #'compute-effective-method #'compute-effective-method-function #'make-method-lambda
          #+allegro #'compute-discriminating-function))

  (defun only-standard-methods (gf &rest other-gfs)
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    (declare (optimize (speed 3) (space 0) (compilation-speed 0)))
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    (loop for other-gf in (or other-gfs *standard-gfs*)
          always (loop for method in (generic-function-methods other-gf)
                       for specializer = (first (method-specializers method))
                       if (and (typep specializer 'class)
                               (subclassp specializer (find-class 'standard-generic-function))
                               (not (eq specializer (find-class 'standard-generic-function)))
                               (typep gf specializer))
                       return nil
                       else if (and (typep specializer 'eql-specializer)
                                    (eql (eql-specializer-object specializer) gf))
                       return nil
                       finally (return t))))

  (defun methods-all-the-same-specializers (gf)
    (declare (optimize (speed 3) (space 0) (compilation-speed 0)))
    (loop with template = (first (generic-function-methods gf))
          for method in (rest (generic-function-methods gf))
          always (loop for spec1 in (method-specializers template)
                       for spec2 in (method-specializers method)
                       always (etypecase spec1
                                (class (etypecase spec2
                                         (class (eq spec1 spec2))
                                         (eql-specializer nil)))
                                (eql-specializer
                                 (etypecase spec2
                                   (class nil)
                                   (eql-specializer
                                    (eql (eql-specializer-object spec1)
                                         (eql-specializer-object spec2)))))))))

  (defun compute-discriminator (gf compute-native-discriminator)
    (declare (optimize (speed 3) (space 0) (compilation-speed 0)))
    (let ((nof-required-args (length (required-args (generic-function-lambda-list gf))))
          discriminator)
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      #+(or clozure ecl lispworks)
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      (setf (argument-order gf)
            (compute-argument-order gf nof-required-args))
      (flet ((discriminate (emf-setter args &optional (classes (loop for arg in args
                                                                     repeat nof-required-args
                                                                     collect (class-of arg))))
               (declare (type list args classes) (type function emf-setter))
               (multiple-value-bind (emf validp) (get-emf-using-classes gf args classes nof-required-args)
                 (funcall emf-setter (if validp emf (lambda (&rest args)
                                                      (apply (the function (get-emf gf args nof-required-args)) args))))
                 (apply (the function emf) args))))
        (when (only-standard-methods gf #'compute-applicable-methods #'compute-applicable-methods-using-classes)
          (setq discriminator
                (if (only-standard-methods
                     gf #'compute-effective-method #'compute-effective-method-function #'make-method-lambda
                     #+allegro #'compute-discriminating-function)
                  (funcall compute-native-discriminator)
                  (let ((argument-order
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                         #-(or clozure ecl lispworks) (compute-argument-order gf nof-required-args)
                         #+(or clozure ecl lispworks) (argument-order gf)))
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                    (cond ((null (generic-function-methods gf))
                           (lambda (&rest args)
                             (apply #'no-applicable-method gf args)))
                          ((methods-all-the-same-specializers gf)
                           (let ((specializers (method-specializers (first (generic-function-methods gf))))
                                 (effective-method-function nil))
                             (declare (type list specializers))
                             (lambda (&rest args)
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                               (declare (optimize (speed 3) (safety 0) (debug 0)
                                                  (compilation-speed 0)))
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                               (cond ((loop for arg in args
                                            for spec in specializers
                                            always (etypecase spec
                                                     (class (typep arg spec))
                                                     (eql-specializer (eql arg (eql-specializer-object spec)))))
                                      (if effective-method-function
                                        (apply (the function effective-method-function) args)
                                        (discriminate (lambda (emf) (setq effective-method-function emf)) args)))
                                     (t (apply #'no-applicable-method gf args))))))
                          ((= (length argument-order) 1)
                           (let ((dispatch-argument-index (svref argument-order 0))
                                 (emfs (make-hash-table :test #'eq)))
                             (declare (type hash-table emfs) (type fixnum dispatch-argument-index))
                             (lambda (&rest args)
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                               (declare (optimize (speed 3) (safety 0) (debug 0)
                                                  (compilation-speed 0)))
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                               (let* ((dispatch-class (class-of (nth dispatch-argument-index args)))
                                      (effective-method-function (gethash dispatch-class emfs)))
                                 (if effective-method-function
                                   (apply (the function effective-method-function) args)
                                   (discriminate (lambda (emf) (setf (gethash dispatch-class emfs) emf)) args)))))))))))
        (if discriminator discriminator
          (let ((emfs (make-hash-table :test #'equal)))
            (declare (type hash-table emfs))
            (lambda (&rest args)
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              (declare (optimize (speed 3) (safety 0) (debug 0)
                                 (compilation-speed 0)))
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              (let* ((classes (loop for arg in args
                                    repeat nof-required-args
                                    collect (class-of arg)))
                     (effective-method-function (gethash (the list classes) emfs)))
                (if effective-method-function
                  (apply (the function effective-method-function) args)
                  (discriminate (lambda (emf) (setf (gethash (the list classes) emfs) emf)) args classes)))))))))

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  #-(or clisp lispworks)
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  (cl:defmethod compute-discriminating-function ((gf standard-generic-function))
    (if (eq (class-of gf) (find-class 'standard-generic-function))
      (lambda (&rest args)
        (let ((discriminator (compute-discriminator gf #'call-next-method)))
          (set-funcallable-instance-function gf discriminator)
          (apply discriminator args)))
      (compute-discriminator gf #'call-next-method)))

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  #+(or clisp lispworks)
  (cl:defmethod compute-discriminating-function ((gf standard-generic-function))
    (compute-discriminator gf #'call-next-method))

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  #-sbcl
  (progn
    (defun maybe-remove-initial-methods (function-name)
      (let ((generic-function (ignore-errors (fdefinition function-name))))
        (when (and generic-function (typep generic-function 'standard-generic-function))
          (dolist (method (slot-value generic-function 'initial-methods))
            (remove-method generic-function method)))))

    #-(or allegro lispworks)
    (defmacro without-redefinition-warnings (&body body)
      `(progn ,@body))
    
    #+allegro
    (defmacro without-redefinition-warnings (&body body)
      `(excl:without-redefinition-warnings ,@body))

    #+lispworks
    (defmacro without-redefinition-warnings (&body body)
      `(let ((dspec:*redefinition-action* :quiet)) ,@body))
    
    (defmacro defgeneric (&whole form name (&rest args) &body options &environment env)
      (loop initially (unless (every #'consp options)
                        (error "Illegal options in defgeneric form ~S." form))
            with generic-function-class-name = nil
            for option in options
            if (eq (car option) :generic-function-class) do
            (when (or (cddr option) (null (cadr option)) (not (symbolp (cadr option)))
                      generic-function-class-name)
              (error "Illegal or duplicate :generic-function-class option in defgeneric form ~S." form))
            (setq generic-function-class-name (cadr option))
            end
            if (eq (car option) :method) collect option into method-options
            else collect option into non-method-options
            finally
            (let ((gf (gensym))
                  (non-standard (when generic-function-class-name
                                  (let ((standard-generic-function (find-class 'standard-generic-function t env))
                                        (this-generic-function (find-class generic-function-class-name t env)))
                                    (and (subclassp this-generic-function standard-generic-function)
                                         (not (eq this-generic-function standard-generic-function)))))))
              (return-from defgeneric
                `(progn (maybe-remove-initial-methods ',name)
                   ,(if non-standard
                      `(eval-when (:compile-toplevel :load-toplevel :execute)
                         (cl:defgeneric ,name ,args ,@non-method-options))
                      `(progn
                         (eval-when (:compile-toplevel)
                           (cl:defgeneric ,name ,args ,@non-method-options))
                         (eval-when (:load-toplevel :execute)
                           (without-redefinition-warnings
                             (cl:defgeneric ,name ,args ,@options)))))
                   (let ((,gf (fdefinition ',name)))
                     ,(when non-standard
                        `(setf (slot-value ,gf 'initial-methods)
                               (list ,@(loop for method-option in method-options
                                             collect `(defmethod ,name ,@(cdr method-option))))))
                     ,gf)))))))

  #+sbcl
  (defmacro defgeneric (&whole form name (&rest args) &body options)
    (unless (every #'consp options)
      (error "Illegal generic function options in defgeneric form ~S." form))
    (let ((options-without-methods (remove :method options :key #'car :test #'eq)))
      `(progn
         (eval-when (:compile-toplevel)
           (cl:defgeneric ,name ,args ,@options-without-methods))
         (eval-when (:load-toplevel :execute)
           (cl:defgeneric ,name ,args ,@options)))))

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  #-sbcl
  (progn
    (defun create-gf-lambda-list (method-lambda-list)
      (loop with stop-keywords = '#.(remove '&optional lambda-list-keywords)
            for arg in method-lambda-list
            until (member arg stop-keywords)
            collect arg into gf-lambda-list
            finally (return (let (rest)
                              (cond ((member '&key method-lambda-list)
                                     (nconc gf-lambda-list '(&key)))
                                    ((setq rest (member '&rest method-lambda-list))
                                     (nconc gf-lambda-list (subseq rest 0 2)))
                                    (t gf-lambda-list))))))
    
    (defun extract-specializers (specialized-args form)
      (loop for specializer-name in (extract-specializer-names specialized-args)
            collect (typecase specializer-name
                      (symbol `(find-class ',specializer-name))
                      (class specializer-name)
                      (cons (cond
                             ((> (length specializer-name) 2)
                              (error "Invalid specializer ~S in defmethod form ~S."
                                     specializer-name form))
                             ((eq (car specializer-name) 'eql)
                              `(intern-eql-specializer ,(cadr specializer-name)))
                             (t (error "Invalid specializer ~S in defmethod form ~S."
                                       specializer-name form))))
                      (t (error "Invalid specializer ~S in defmethod form ~S."
                                specializer-name form)))))
    
    (defun load-method (name gf-lambda-list type qualifiers specializers lambda-list function options)
      (let* ((gf (if (fboundp name) (fdefinition name)
                   (ensure-generic-function name :lambda-list gf-lambda-list :generic-function-class type)))
             (method (apply #'make-instance
                            (generic-function-method-class gf)
                            :qualifiers qualifiers
                            :specializers specializers
                            :lambda-list lambda-list
                            :function function
                            options)))
        (add-method gf method)
        method)))
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  (define-condition defmethod-without-generic-function (style-warning)
    ((name :initarg :name :reader dwg-name))
    (:report (lambda (c s) (format s "No generic function present when encountering a defmethod for ~S. Assuming it will be an instance of standard-generic-function." (dwg-name c)))))

  (define-symbol-macro warn-on-defmethod-without-generic-function
    #-sbcl t
    #+sbcl nil)

  #-sbcl
  (defmacro defmethod (&whole form name &body body &environment env)
    (loop with generic-function = (when (fboundp name) (fdefinition name))
        
          initially
          (when (macroexpand 'warn-on-defmethod-without-generic-function env)
            (unless generic-function
              (warn 'defmethod-without-generic-function :name name)))
          (unless (typep generic-function 'standard-generic-function)
            (return-from defmethod `(cl:defmethod ,@(cdr form))))
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          #-ecl
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          (when (only-standard-methods generic-function)
            (return-from defmethod `(cl:defmethod ,@(cdr form))))

          for tail = body then (cdr tail)
          until (listp (car tail))
          collect (car tail) into qualifiers
          finally
          (destructuring-bind
              ((&rest specialized-args) &body body) tail
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            (multiple-value-bind
                (documentation declarations main-body)
                (parse-method-body body form)
              (let* ((lambda-list (extract-lambda-list specialized-args))
                     (gf-lambda-list (create-gf-lambda-list lambda-list))
                     (specializers (extract-specializers specialized-args form))
                     (method-class (generic-function-method-class generic-function)))
                #+allegro (ensure-finalized method-class)
                (multiple-value-bind
                    (method-lambda method-options)
                    (make-method-lambda generic-function (class-prototype method-class)
                                        `(lambda ,lambda-list
                                           ,@(when documentation (list documentation))
                                           (declare ,@declarations)
                                           (declare (ignorable ,@(loop for arg in specialized-args
                                                                       until (member arg lambda-list-keywords)
                                                                       when (consp arg) collect (car arg))))
                                           (block ,(if (consp name) (cadr name) name) ,@main-body))
                                        env)
                  (return-from defmethod
                    `(load-method ',name ',gf-lambda-list ',(type-of generic-function)
                                  ',qualifiers (list ,@specializers) ',lambda-list
                                  (function ,method-lambda) ',method-options))))))))
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  #+sbcl
  (defmacro defmethod (&whole form name &body body &environment env)
    (declare (ignore body))
    (let ((generic-function (when (fboundp name) (fdefinition name))))
      (when (macroexpand 'warn-on-defmethod-without-generic-function env)
        (unless generic-function
          (warn 'defmethod-without-generic-function :name name)))
      `(cl:defmethod ,@(cdr form))))
)

#+(or allegro clisp cmu mcl scl)
(defun ensure-method (gf lambda-expression 
                         &key (qualifiers ())
                         (lambda-list (cadr lambda-expression))
                         (specializers (required-args lambda-list (constantly (find-class 't)))))
  
  (let ((form `(defmethod ,(generic-function-name gf) ,@qualifiers
                 ,(loop for specializer in specializers
                        for (arg . rest) on lambda-list
                        collect `(,arg ,specializer) into args
                        finally (return (nconc args rest)))
                 ,@(cddr lambda-expression))))
    
    #+(or allegro clisp cmu scl)
    (funcall (compile nil `(lambda () ,form)))
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    #+mcl (eval form)))

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(defun ensure-method (gf lambda-expression
                         &key (method-class (generic-function-method-class gf))
                         (qualifiers ())
                         (lambda-list (cadr lambda-expression))
                         (specializers (required-args lambda-list (constantly (find-class 't)))))
  (multiple-value-bind
      (method-lambda method-args)
      (make-method-lambda
       gf (class-prototype method-class)
       lambda-expression ())
    (let ((method (apply #'make-instance
                         method-class
                         :qualifiers qualifiers
                         :lambda-list lambda-list
                         :specializers specializers
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                         :function
                         #-ecl (compile nil method-lambda)
                         #+ecl (coerce method-lambda 'function)
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                         method-args)))
      (add-method gf method)
      method)))

;; The following can be used in direct-slot-definition-class to get the correct initargs
;; for a slot. Use it like this:
;;
;; (defmethod direct-slot-definition-class
;;            ((class my-standard-class) &rest initargs)
;;   (destructuring-bind
;;       (&key key-of-interest &allow-other-keys)
;;       (fix-slot-initargs initargs)
;;     ...))

(defvar *standard-slot-keys*
  '(:name :documentation
    :initargs :initform :initfunction
    :readers :writers))

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(define-modify-macro nconcf (&rest lists) nconc)

(defun fix-slot-initargs (initargs)
  #+(or allegro clisp clozure lispworks mcl sbcl)
  initargs

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  (let* ((counts (loop with counts
                       for (key nil) on initargs by #'cddr
                       do (incf (getf counts key 0))
                       finally (return counts)))
         (keys-to-fix (loop for (key value) on counts by #'cddr
                            if (> value 1) collect key)))
    (if keys-to-fix
      (let ((multiple-standard-keys
             (intersection keys-to-fix *standard-slot-keys*)))
        (if multiple-standard-keys
          (error "Too many occurences of ~S in slot initargs ~S."
                 multiple-standard-keys initargs)
          (loop with fixed-keys
                for (key value) on initargs by #'cddr
                if (member key keys-to-fix)
                do (nconcf (getf fixed-keys key) (list value))
                else nconc (list key value) into fixed-initargs
                finally (return (nconc fixed-initargs fixed-keys)))))
      initargs)))