I must be missing something obvious. But I've developed short-term macro 

The idea is that the `foo` identifier is packaged into the call to `submac` as 
a syntax property.

When I retrieve this property from inside `mac`, it returns the expected 
'module-foo value.

But when I retrieve this property from inside `submac`, it creates a new 
nonconflicting variable. This confuses me: what I expect is that `submac` 
should try to bind the same identifier, producing an error.


#lang racket

(define foo 'module-foo)

(define-syntax (mac stx)
  (syntax-case stx ()
    [(_ SUBMAC)
     (with-syntax ([SUBMAC (syntax-property #'SUBMAC 'foo-id #'foo)])
       #`(begin (displayln (format "module foo = ~a" #,(syntax-property 
#'SUBMAC 'foo-id)))

(define-syntax (submac stx)
  (syntax-case stx ()
     (with-syntax ([FOO-ID (syntax-property stx 'foo-id)])
           (define FOO-ID 'submac-foo)
           (displayln (format "submac foo = ~a" FOO-ID))))]))

(mac (submac)) ; why not an "identifier already defined" error?

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