If you put the code below in a module, you don't get an error, because the syntax object that has the unsealed context doesn't appear in the fully-expanded module. The syntax object is in a local macro binding that disappears.
If you remove the `let' around (bind h (define q 5)) (define q 8) (nab h) then the relevant syntax object remains in the fully expanded result, and you get an error. At Fri, 15 Aug 2014 14:33:35 -0400, Stephen Chang wrote: > The docs say that if I make an internal definition context with > syntax-local-make-definition-context, I have to seal it with > internal-definition-context-seal, otherwise an exception gets raised. > But I can't get this to happen. Does someone have an example that > causes the exception to get thrown? > > For example, this program from the racket tests produces the same > result if I comment out the seal line. Other tests behave similarly. > > (define-syntax (bind stx) > (syntax-case stx () > [(_ handle def) > (let ([def-ctx (syntax-local-make-definition-context)] > [ctx (cons (gensym 'intdef) > (let ([orig-ctx (syntax-local-context)]) > (if (pair? orig-ctx) > orig-ctx > null)))] > [kernel-forms (list #'define-values)]) > (let ([def (local-expand #'def ctx kernel-forms def-ctx)]) > (syntax-case def () > [(define-values (id) rhs) > (begin > (syntax-local-bind-syntaxes (list #'id) #f def-ctx) > (internal-definition-context-seal def-ctx) > #'(begin > (define-values (id) rhs) > (define-syntax handle (quote-syntax id))))] > [_ (error "no")])))])) > > (define-syntax (nab stx) > (syntax-case stx () > [(_ handle) > (syntax-local-value #'handle)])) > > (let () > (bind h (define q 5)) > (define q 8) > (nab h)) > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev _________________________ Racket Developers list: http://lists.racket-lang.org/dev
