From fd074a439d7a5ef676d47d950d5d701d04e780fb Mon Sep 17 00:00:00 2001
From: Oleg Grenrus <oleg.grenrus@iki.fi>
Date: Sun, 19 Jun 2022 23:55:00 +0300
Subject: [PATCH] Change RnfArgs to be data family

Then we don't rely that heavily on simplifier to remove the GADT
overhead. Even when unoptimized, there isn't additional
box over RnfArgs1.

I did similar change to hashable in 2019.
---
 Control/DeepSeq.hs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Control/DeepSeq.hs b/Control/DeepSeq.hs
index 84af949..d32b7e8 100644
--- a/Control/DeepSeq.hs
+++ b/Control/DeepSeq.hs
@@ -3,9 +3,9 @@
 {-# LANGUAGE DefaultSignatures #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE GADTs #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE Safe #-}
+{-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE PolyKinds #-}
 {-# LANGUAGE EmptyCase #-}
@@ -152,9 +152,9 @@ instance GNFData arity V1 where
 data Zero
 data One
 
-data RnfArgs arity a where
-  RnfArgs0 :: RnfArgs Zero a
-  RnfArgs1  :: (a -> ()) -> RnfArgs One a
+data family RnfArgs arity a
+data instance RnfArgs Zero a = RnfArgs0
+newtype instance RnfArgs One a = RnfArgs1 (a -> ())
 
 instance GNFData arity U1 where
   grnf _ U1 = ()