--- /dev/null
+(in-package "SPECIALIZABLE")
+
+(defclass binding ()
+ ((used :initform nil :accessor used)))
+
+(defun make-env (bindings env)
+ (append bindings env))
+(defun find-binding (env var)
+ (cdr (assoc var env)))
+
+(defun bindings-from-ll (ll)
+ (mapcar (lambda (n) (cons n (make-instance 'binding))) ll))
+
+(define-condition walker-warning (warning)
+ ((env :initarg :env :reader env)
+ (call-stack :initarg :call-stack :reader call-stack)))
+(define-condition unused-variable (walker-warning)
+ ((name :initarg :name :reader name)))
+(define-condition unbound-variable-referenced (walker-warning)
+ ((name :initarg :name :reader name)))
+
+(fmakunbound 'walk)
+(defgeneric walk (form env vars)
+ (:generic-function-class cons-generic-function))
+
+(defmethod walk ((expr cons) env call-stack)
+ (let ((cs (cons expr call-stack)))
+ (when (consp (car expr))
+ (walk (car expr) env cs))
+ (dolist (e (cdr expr))
+ (walk e env (cons e cs)))))
+(defmethod walk ((expr symbol) env call-stack)
+ (if (constantp expr)
+ nil
+ (let ((binding (find-binding env expr)))
+ (if binding
+ (setf (used binding) t)
+ (warn 'unbound-variable-referenced :name expr
+ :env env :call-stack call-stack)))))
+(defmethod walk ((expr t) env call-stack)
+ nil)
+(defmacro with-checked-bindings ((bindings env call-stack) &body body)
+ `(let* ((bindings ,bindings)
+ (,env (make-env bindings ,env)))
+ ,@body
+ (dolist (binding bindings)
+ (unless (used (cdr binding))
+ (warn 'unused-variable :name (car binding)
+ :env ,env :call-stack ,call-stack)))))
+(defmethod walk ((expr (cons lambda)) env call-stack)
+ (let ((lambda-list (cadr expr))
+ (body (cddr expr)))
+ (with-checked-bindings ((bindings-from-ll lambda-list) env call-stack)
+ (dolist (form body)
+ (walk form env (cons form call-stack))))))
+(defmethod walk ((expr (cons multiple-value-bind)) env call-stack)
+ (let ((lambda-list (cadr expr))
+ (value-form (caddr expr))
+ (body (cdddr expr)))
+ (walk value-form env (cons value-form call-stack))
+ (with-checked-bindings ((bindings-from-ll lambda-list) env call-stack)
+ (dolist (form body)
+ (walk form env (cons form call-stack))))))
+(defmethod walk ((expr (cons let)) env call-stack)
+ (with-checked-bindings ((mapcar (lambda (x) (walk (cadr x) env (cons (cadr x) call-stack)) (cons (car x) (make-instance 'binding))) (cadr expr)) env call-stack)
+ (dolist (form (cddr expr))
+ (walk form env (cons form call-stack)))))
+
+(defun walk/case (expr env call-stack)
+ (typecase expr
+ (symbol
+ (if (constantp expr)
+ nil
+ (let ((binding (find-binding env expr)))
+ (if binding
+ (setf (used binding) t)
+ (warn 'unbound-variable-referenced :name expr
+ :env env :call-stack call-stack)))))
+ ((cons (eql lambda))
+ (let ((lambda-list (cadr expr))
+ (body (cddr expr)))
+ (with-checked-bindings ((bindings-from-ll lambda-list) env call-stack)
+ (dolist (form body)
+ (walk/case form env (cons form call-stack))))))
+ ((cons (eql multiple-value-bind))
+ (let ((lambda-list (cadr expr))
+ (value-form (caddr expr))
+ (body (cdddr expr)))
+ (walk/case value-form env (cons value-form call-stack))
+ (with-checked-bindings ((bindings-from-ll lambda-list) env call-stack)
+ (dolist (form body)
+ (walk/case form env (cons form call-stack))))))
+ ((cons (eql macrolet)))
+ ((cons (eql flet)))
+ ((cons (eql labels)))
+ ((cons (eql symbol-macrolet)))
+ ((cons (eql if)))
+ ((cons (eql progn)))
+ ((cons (eql tagbody)))
+ ((cons (eql return-from)))
+ ((cons (eql multiple-value-call)))
+ ((cons (eql block)))
+ ((cons (eql catch)))
+ ((cons (eql throw)))
+ ((cons (eql let))
+ (with-checked-bindings ((mapcar (lambda (x) (walk/case (cadr x) env (cons (cadr x) call-stack)) (cons (car x) (make-instance 'binding))) (cadr expr)) env call-stack)
+ (dolist (form (cddr expr))
+ (walk/case form env (cons form call-stack)))))
+ (cons
+ (let ((cs (cons expr call-stack)))
+ (when (consp (car expr))
+ (walk/case (car expr) env cs))
+ (dolist (e (cdr expr))
+ (walk/case e env (cons e cs)))))
+ (t)))
+
+(defgeneric walk/meth (expr env call-stack))
+
+(defmethod walk/meth ((expr symbol) env call-stack)
+ (if (constantp expr)
+ nil
+ (let ((binding (find-binding env expr)))
+ (if binding
+ (setf (used binding) t)
+ (warn 'unbound-variable-referenced :name expr
+ :env env :call-stack call-stack)))))
+(defmethod walk/meth ((expr t) env call-stack)
+ nil)
+
+(defmethod walk/meth ((expr cons) env call-stack)
+ (typecase expr
+ ((cons (eql lambda))
+ (let ((lambda-list (cadr expr))
+ (body (cddr expr)))
+ (with-checked-bindings ((bindings-from-ll lambda-list) env call-stack)
+ (dolist (form body)
+ (walk/meth form env (cons form call-stack))))))
+ ((cons (eql multiple-value-bind))
+ (let ((lambda-list (cadr expr))
+ (value-form (caddr expr))
+ (body (cdddr expr)))
+ (walk/meth value-form env (cons value-form call-stack))
+ (with-checked-bindings ((bindings-from-ll lambda-list) env call-stack)
+ (dolist (form body)
+ (walk/meth form env (cons form call-stack))))))
+ ((cons (eql macrolet)))
+ ((cons (eql flet)))
+ ((cons (eql labels)))
+ ((cons (eql symbol-macrolet)))
+ ((cons (eql if)))
+ ((cons (eql progn)))
+ ((cons (eql tagbody)))
+ ((cons (eql return-from)))
+ ((cons (eql multiple-value-call)))
+ ((cons (eql block)))
+ ((cons (eql catch)))
+ ((cons (eql throw)))
+ ((cons (eql let))
+ (with-checked-bindings ((mapcar (lambda (x) (walk/meth (cadr x) env (cons (cadr x) call-stack)) (cons (car x) (make-instance 'binding))) (cadr expr)) env call-stack)
+ (dolist (form (cddr expr))
+ (walk/meth form env (cons form call-stack)))))
+ (t
+ (let ((cs (cons expr call-stack)))
+ (when (consp (car expr))
+ (walk/meth (car expr) env cs))
+ (dolist (e (cdr expr))
+ (walk/meth e env (cons e cs)))))))
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