From d462a25bd19d5a8b80f69d918c488e0dee106222 Mon Sep 17 00:00:00 2001
From: Eli Barzilay <eli@barzilay.org>
Date: Sat, 16 Apr 2005 18:59:42 +0000
Subject: [PATCH] .

original commit: 1e66762202bc42766ae64dac137ace0c89d878db
---
 collects/mzlib/foreign.ss | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/collects/mzlib/foreign.ss b/collects/mzlib/foreign.ss
index dcb7dcb..db523ac 100644
--- a/collects/mzlib/foreign.ss
+++ b/collects/mzlib/foreign.ss
@@ -464,6 +464,11 @@
 ;; `-> expr'               specify different output, can use previous names
 ;; Also, see below for custom function types.
 
+(provide ->) ; to signal better errors when trying to use this with contracts
+(define-syntax ->
+  (syntax-id-rules ()
+    [_ (raise-syntax-error '-> "should be used only in a _fun context")]))
+
 (provide _fun)
 (define-syntax (_fun stx)
   (define (err msg . sub) (apply raise-syntax-error '_fun msg stx sub))