[racket] syntax-local-value mystery

Could someone explain why the program below raises a syntax error?

The error goes away if you make either of the following changes:

1. enable errortrace, or
2. change `syntax' to `quote' in the `expand' argument.

;;;;

#lang racket/load

; Change #1
;(require errortrace)

(module t racket
  (provide (struct-out src))
  (struct src (line col)))

(module r racket
  (require (for-syntax 't))
  (provide def use)
  (define-syntax (def stx)
    (syntax-case stx ()
      [(_ x)
       (identifier? #'x)
       #`(define-syntax x
           (src #,(syntax-line stx) #,(syntax-column stx)))]))
  (define-syntax (use stx)
    (syntax-case stx ()
      [(_ x)
       (identifier? #'x)
       (let ([src (syntax-local-value #'x (λ () #f))])
         (if src
             #`(format "~a at ~a:~a"
                       '#,(syntax-e #'x)
                       #,(src-line src)
                       #,(src-col src))
             (raise-syntax-error #f "no def" stx #'x)))])))

(module u racket
  (require 'r)
  (define-namespace-anchor module-anchor)
  (parameterize ([current-namespace (namespace-anchor->namespace
module-anchor)])
    (eval #'
          ; Change #2
          ;'
          (module m racket
              (require 'r)
              (def x)
              (use x)))
    (eval '(require 'm))))

(require 'u)