From e5523324d2c55e0091857e21bf5613b5f6b442a7 Mon Sep 17 00:00:00 2001
From: Sylvain Henry <sylvain@haskus.fr>
Date: Wed, 30 Sep 2020 19:26:02 +0200
Subject: Bignum: add integerNegate RULE

---
 libraries/ghc-bignum/src/GHC/Num/Integer.hs | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'libraries')

diff --git a/libraries/ghc-bignum/src/GHC/Num/Integer.hs b/libraries/ghc-bignum/src/GHC/Num/Integer.hs
index 43e4a18cdd..daa7ab8388 100644
--- a/libraries/ghc-bignum/src/GHC/Num/Integer.hs
+++ b/libraries/ghc-bignum/src/GHC/Num/Integer.hs
@@ -486,6 +486,9 @@ integerNegate (IP b)
   | isTrue# (bigNatEqWord# b ABS_INT_MINBOUND##) = IS INT_MINBOUND#
   | True                                         = IN b
 
+{-# RULES
+"integerNegate/integerNegate" forall x. integerNegate (integerNegate x) = x
+#-}
 
 -- | Compute absolute value of an 'Integer'
 integerAbs :: Integer -> Integer
-- 
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