From 04e8e33313842d94d0cbff458ad23047ee1441fc Mon Sep 17 00:00:00 2001
From: Asumu Takikawa <asumu@ccs.neu.edu>
Date: Tue, 4 Dec 2012 15:33:02 -0500
Subject: [PATCH] Provide a more informative internal error

---
 collects/typed-racket/types/substitute.rkt | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/collects/typed-racket/types/substitute.rkt b/collects/typed-racket/types/substitute.rkt
index 55f327e61d..0810ba4488 100644
--- a/collects/typed-racket/types/substitute.rkt
+++ b/collects/typed-racket/types/substitute.rkt
@@ -48,7 +48,13 @@
                  [#:F name (hash-ref subst name target)]
                  [#:arr dom rng rest drest kws
                         (cond
-                          [(and (pair? drest) (ormap (and/c (cdr drest) (not/c bound-tvar?)) names)) =>
+                          [(and (pair? drest)
+                                (ormap (λ (name)
+                                          (and (equal? name (cdr drest))
+                                               (not (bound-tvar? name))
+                                               name))
+                                       names))
+                           =>
                            (lambda (name)
                              (int-err "substitute used on ... variable ~a in type ~a" name target))]
                           [else