[Bug-mit-scheme] [bug #55090] 9.2 -> 10.1 breaks macro by skipping some variable renaming

[Arthur A. Gleckler]

URL:
  <https://savannah.gnu.org/bugs/?55090>

                 Summary: 9.2 -> 10.1 breaks macro by skipping some variable
renaming
                 Project: MIT/GNU Scheme
            Submitted by: aag
            Submitted on: Sat 24 Nov 2018 11:50:55 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:

While porting my code to 10.1, I've found one macro that no longer works.  The
problem is that one variable is no longer renamed upon a recursive macro call.
 Since the same macro worked under 9.2 and with other syntax-rules
implementations (e.g. it's part of the implementation of SRFI 146, which runs
on other Schemes), I'm fairly confident that this is a bug.

For this bug report, I've pared the macro down to this:


(define-syntax vector-edit-code
  (syntax-rules ()
    ((_ v r o s)
     (let ((index (vector-length v)))
       (subvector-move-left! v o index r (+ o s))
       r))
    ((_ v r o s i e)
     (let ((index i))
       (subvector-move-left! v o index r (+ o s))
       (vector-set! r (+ s index) e)
       (let ((skew (1+ s)))
         (vector-edit-code v r index skew))))))


Here's an example:


(pp (lambda () (let ((input (vector 0 1 3))) (let ((array (make-vector 4)))
(vector-edit-code input array 0 0 2 2)))))


In 9.2, evaluating that expression produces:


(lambda ()
  (let ((input (vector 0 1 3)))
    (let ((array (make-vector 4)))
      (let ((index 2))
        (subvector-move-left! input 0 index array (+ 0 0))
        (vector-set! array (+ 0 index) 2)
        (let ((skew (1+ 0)))
          (let ((.index.1-0 (vector-length input)))
            (subvector-move-left! input index .index.1-0 array (+ index
skew))
            array))))))


In 10.1, evaluating the same form produces:


(lambda ()
  (let ((input (vector 0 1 3)))
    (let ((array (make-vector 4)))
      (let ((index 2))
        (subvector-move-left! input 0 index array (+ 0 0))
        (vector-set! array (+ 0 index) 2)
        (let ((skew (|1+| 0)))
          (let ((index (vector-length input)))
            (subvector-move-left! input index index array (+ index skew))
            array))))))


The inner use of the identifier index does not get renamed, which makes the
calculation fail.




    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?55090>

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