Gauche と Scheme で結果が異なる。 ネストしている箇所の処理に何か違いが…？

let-scope.scm

(define (traverse proc obj)
  (let loop ((obj obj))
    (cond ((or (identifier? obj) (symbol? obj))
           (proc obj))
          ((pair? obj)
           (cons (loop (car obj)) (loop (cdr obj))))
          ((vector? obj)
           (vector-map loop obj))
          (else obj))))

(define-syntax let/scope
  (er-macro-transformer
   (lambda(form rename _)
     (let ((scope (cadr form))
           (body (cddr form)))
       `(let-syntax ((,scope
                      (,(rename 'er-macro-transformer)
                       (,(rename 'lambda) (f r _)
                        (,(rename 'let) ((form2 (,(rename 'cdr) f)))
                         (,(rename 'cons)
                          ',(rename 'begin)
                          (,(rename 'traverse) r form2)))))))
          ,@body)))))

(let ((x 1))
  (let/scope scope-1
    (let ((x 2))
      (let/scope scope-2
        (let ((x 3))
          (let/scope scope-1
            (let ((x 4))
              (display (scope-2 (scope-1 x)))
              (display (scope-2 x))
              (display (scope-1 x))
              (display x))))))))