Walker and lexical environment

walker-and-lexenv.lisp

(in-package :cl-user)

(#+sbcl
 sb-walker:walk-form
 #+allegro
 excl::walk-form
 `(let ((x 1))
    (declare (fixnum x))
    :marker)
 nil
 (lambda (subform context env)
   (declare (ignore context))
   (when (eq subform :marker)
     (print
      (multiple-value-list
       #+sbcl
       (sb-cltl2:variable-information 'x env)
       #+allegro
       (sys:variable-information 'x env))))
   subform))
; SBCL:
; (NIL NIL NIL)
; Allegro CL:
; (:LEXICAL NIL ((TYPE (INTEGER -1152921504606846976 1152921504606846975))) T)