Signal error when trying to match against non-existent backref.

original commit: f8a9434cb6d1c3e82742b4090d35d6ebe1ef465d
2005-04-25 14:22:38 +00:00 · 2005-04-25 14:22:38 +00:00 · 4836b4c50e
commit 4836b4c50e
parent e41a34ee34
1 changed files with 10 additions and 2 deletions
--- a/collects/mzlib/pregexp.ss
+++ b/collects/mzlib/pregexp.ss
@ -448,7 +448,16 @@
                  (lambda (i1) (or (sk i1) (loup-or (cdr res))))
                  (lambda () (loup-or (cdr res)))))))
            ((:backref)
-             (let ((backref (cdr (pregexp-list-ref backrefs (cadr re)))))
+             (let* ((c (pregexp-list-ref backrefs (cadr re)))
+                    (backref
+                      (cond
+                       (c => cdr)
+                       (else
+                        (error
+                         'pregexp-match-positions-aux
+                         'non-existent-backref
+                         re)
+                        #f))))
               (if backref
                 (pregexp-string-match
                   (substring s (car backref) (cdr backref))
@ -664,4 +673,3 @@


 )
-