[bug #57785] dropped syntactic closure in 10.90

[Arthur A. Gleckler]

URL:
  <https://savannah.gnu.org/bugs/?57785>

                 Summary: dropped syntactic closure in 10.90
                 Project: MIT/GNU Scheme
            Submitted by: aag
            Submitted on: Mon 10 Feb 2020 08:29:09 PM UTC
                Category: runtime
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect behavior
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                Keywords: 

    _______________________________________________________

Details:

I've been trying to debug a macro that worked under 9.2.1 but fails under
10.90 (76bb84eaa).  I've narrowed the problem down to the following
reproducible test case:


(define-syntax bar
  (sc-macro-transformer
   (lambda (exp env)
     (let ((bindings (let ((sc (close-syntax (cadr exp) env)))
                       (list sc sc))))
       `(let* (,bindings)
         'x)))))

(define-syntax bat
  (syntax-rules ()
    ((_ body ...)
     (let ((md 'quux))
       (bar md)))))

;; Under 9.2.1:

;; 1 ]=> (pp (lambda () (bat x)))
;; (lambda ()
;;   (let ((md 'quux))
;;     (let ((md md))
;;       'x)))
;; ;Unspecified return value
;;
;; 1 ]=>

;; Under 10.90 (76bb84eaa):

;; 1 ]=> (pp (lambda () (bat x)))
;; (lambda ()
;;   (let ((.md.1-0 'quux))
;;     (let ((.md.2-1 md))
;;       'x)))
;; ;Unspecified return value
;;
;; 1 ]=>


Note that the expansion under 10.90 means that (bat x) will fail because the
variable md will be unbound.

Is this a bug in macro expansion in 10.90, or was there a bug in 9.2.1 that
caused my macro to work there?  Or am I hopelessly confused?

Thanks.




    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?57785>

_______________________________________________
  Message sent via Savannah
  https://savannah.gnu.org/