From 2b7f2aea4193106e8ead088bba510b22e5b60fd1 Mon Sep 17 00:00:00 2001
From: Zejun Wu <watashi@fb.com>
Date: Thu, 13 Aug 2020 09:15:22 -0700
Subject: [PATCH] Fix haxl build for ghc-8.2

Summary:
In ghc-8.2, we don't have `mappend = (<>)`.
We need define `mappend` explicitly.

Reviewed By: babyLiyuan

Differential Revision: D23090224

fbshipit-source-id: 13359dad7cd1cd3928aef895625ddfc08bb2478e
---
 Haxl/Core/Monad.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Haxl/Core/Monad.hs b/Haxl/Core/Monad.hs
index 32c6bb3..5e8502e 100644
--- a/Haxl/Core/Monad.hs
+++ b/Haxl/Core/Monad.hs
@@ -808,6 +808,7 @@ instance Semigroup a => Semigroup (GenHaxl u w a) where
 
 instance Monoid a => Monoid (GenHaxl u w a) where
   mempty = pure mempty
+  mappend = liftA2 mappend
 
 blockedBlocked
   :: Env u w