racket hack for reporting shadowed bindings

gistfile1.rkt

#lang racket/base

(require (for-syntax racket/base)
         (only-in racket/base
                  [define orig-define]))

(define-syntax (define stx)
  (syntax-case stx ()
    [(_ x e) 
     (when (identifier-binding #'x)                                 
       (printf "WARNING: ~a shadows an existing name~%" (syntax->datum #'x)))
     #'(orig-define x e)]))

(define x 20)
(define list 0)

(define foo
  (lambda ()
    (define x 10)
    (add1 x)))