bar.rkt

#lang racket

(require "foo.rkt")
(define ns (make-base-namespace))
(define v*
  (let ()
    (parameterize ([current-namespace ns])
       (dynamic-require "foo.rkt" 'v))))

(x? v*) ;; should be #f

foo.rkt

#lang racket
(struct x ())
(define v (x))
(provide v x?)