Don't throw away string-builder's state when building.

diff --git a/src/runtime/ustring.scm b/src/runtime/ustring.scm
index 9b36cef8ecdaf84f10ebbd8eec2a52f0f3db5d73..d8a1a125bcb827bca98ae3e8142ab555d7b08e88 100644 (file)
--- a/src/runtime/ustring.scm
+++ b/src/runtime/ustring.scm
@@ -242,10 +242,7 @@ USA.
        unspecific)
 
       (define (build)
-       (let ((strings (reverse! (cons (string-slice buffer 0 index) buffers))))
-         (set! buffer)
-         (set! buffers)
-         (set! index)
+       (let ((strings (reverse (cons (string-slice buffer 0 index) buffers))))
          (let ((result
                 (do ((strings strings (cdr strings))
                      (n 0 (fix:+ n (string-length (car strings))))