From 9e926d20096aa3648d86ea9b40b939e270fff68a Mon Sep 17 00:00:00 2001
From: Sam Tobin-Hochstadt <samth@racket-lang.org>
Date: Sat, 2 Jun 2012 18:51:51 -0400
Subject: [PATCH] Improve type of `identity`.

Closes PR 12813.

original commit: 8459c22c0106b1dd31531f5dbbfd1ce1e7d65fed
---
 collects/typed-racket/base-env/base-env.rkt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/collects/typed-racket/base-env/base-env.rkt b/collects/typed-racket/base-env/base-env.rkt
index 10219a6b..7a0d94dc 100644
--- a/collects/typed-racket/base-env/base-env.rkt
+++ b/collects/typed-racket/base-env/base-env.rkt
@@ -1357,7 +1357,7 @@
 
 
 ;; scheme/function
-[identity (-poly (a) (-> a a))]
+[identity (-poly (a) (->acc (list a) a null))]
 [const (-poly (a) (-> a (->* '() Univ a)))]
 [negate (-polydots (b) (-> ((list) [b b] . ->... . Univ)
                            ((list) [b b] . ->... . -Boolean)))]