gistfile1.rkt

#lang racket/base
(require (for-syntax racket/base
                     racket/list)
         rackunit)

(let ()
  (define-syntax (123-list stx)
    (define middle-x-stx (second (syntax->list stx)))
    (define x-id (syntax-e middle-x-stx))
    (define new-ctxt-stx (datum->syntax #f 'new-ctxt))
    (datum->syntax
     new-ctxt-stx
     (list (datum->syntax #'123-list 'let)
           (list (list x-id
                       (datum->syntax #'123-list 3)))
           (list (datum->syntax #'123-list '#%app)
                 (datum->syntax #'123-list 'list)
                 (datum->syntax #'123-list x-id)
                 middle-x-stx
                 x-id))))

  (define x 1)
  (let ([x 2])
    (check-equal? (123-list x) (list 1 2 3)))

  (define y 1)
  (let ([y 2])
    (check-equal? (123-list y) (list 1 2 3))))