I get some strange result when I evaluate if two identifiers with
different module-level context are bound-identifier=?. They don't bind
to each other and it's possible to have a different definition for
each one but the result of bound-identifier=? is #t, but I expect to
get a #f. The macro "expand-to-define-show-twice" defines the two
versions of show, with different module-level context.
If the definitions are inside a local definition context, then the
expansion fails with an error, because when the "define" are
transformed into "letrec" the two identifiers bind each other. I
expect that the results are the same that before.
I'm not sure if I understand correctly the binding rules, but this
looks like a strange border case.
Gustavo
;;; file: define-show-twice.rkt
#lang racket/base
(require (for-syntax racket/base))
(provide (all-defined-out))
{define-syntax (check-bound-identifier=? stx)
(syntax-case stx ()
[(_ a b) (datum->syntax stx (bound-identifier=? #'a #'b))])}
{define-syntax (expand-to-define-show-twice stx)
(with-syntax ([show-good (datum->syntax stx 'show)]
[show-bad (syntax-local-introduce (datum->syntax
#'here 'show))])
#'(begin
(define show-good displayln)
(define show-bad displayln)
(show-good "G")
(show-bad "B")
(displayln (check-bound-identifier=? show-good show-bad))
))}
;;; end file: define-show-twice.rkt
;;; file: example.rkt
#lang racket/base
(require "define-show-twice.rkt")
(expand-to-define-show-twice)
;==> G B #t
;exp. ==> G B #f?
;(let () (expand-to-define-show-twice))
; ==> error: internal definition: duplicate binding name in: show
;exp. ==> G B #f??
;;; end file: example.rkt
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