(defpackage #:clsafe
  (:use #:cl)
  (:shadow :defmethod :setq :setf :set)
  (:export ))

(in-package #:clsafe)

(defmacro lexical-boundp (symbol)
  `(if (ignore-errors (or (null ,symbol)
			  (not (null ,symbol))))
       t
       nil))

(defun specialp (symbol)
  (or (boundp symbol)
      (eval `(let ((,symbol ))
               (boundp ',symbol)))))


(defmacro setq (&rest pairs)
  `(and ,@(loop :for (symbol value) :on pairs :by #'cddr
		:collect
		`(or (lexical-boundp ,symbol)
		     (specialp ',symbol)
		     (error "Variable ~A doesn't exist." ',symbol)))
	(cl:setq ,@pairs)))

(specialp '*standard-output*);=>t
(specialp '*yyy);=>nil
(lexical-boundp *yyy*);=>nil
(defvar *y*)
(specialp '*y*);=>t
(lexical-boundp *y*);=>nil
(setq *y* 3);=>3
(lexical-boundp *y*);=>t
(setq a 3);The variable A doesn't exist. [Condition of type SIMPLE-ERROR

(let ((a))
  (lexical-boundp a) ;=>t
  (setq a 5)) ;=>5