From d9b084b86c99749a801ca4cbb16cf201fa027ed1 Mon Sep 17 00:00:00 2001
From: Zejun Wu <watashi@fb.com>
Date: Tue, 29 Dec 2015 14:40:34 -0800
Subject: [PATCH] Do not require Show for memoFingerprintKey

Summary:
We don't need memoized value to be showable. By removing this constrait,
we no longer require deriving `Show` for many user-defined data types
and we support values like `Haxl a` which doesn't have a proper `Show`
instance.

Differential Revision: D2793617

fbshipit-source-id: f4958ca83eda97d4a27f4e1544a1078039ce6875
---
 Haxl/Core/Memo.hs  | 4 +---
 Haxl/Core/Monad.hs | 2 +-
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/Haxl/Core/Memo.hs b/Haxl/Core/Memo.hs
index d907bf3..fa4a731 100644
--- a/Haxl/Core/Memo.hs
+++ b/Haxl/Core/Memo.hs
@@ -55,7 +55,6 @@ data MemoTextKey a where
   deriving Typeable
 
 deriving instance Eq (MemoTextKey a)
-deriving instance Show (MemoTextKey a)
 
 instance Hashable (MemoTextKey a) where
   hashWithSalt s (MemoText t) = hashWithSalt s t
@@ -73,7 +72,6 @@ data MemoFingerprintKey a where
   deriving Typeable
 
 deriving instance Eq (MemoFingerprintKey a)
-deriving instance Show (MemoFingerprintKey a)
 
 instance Hashable (MemoFingerprintKey a) where
   hashWithSalt s (MemoFingerprintKey x _) =
@@ -89,5 +87,5 @@ instance Hashable (MemoFingerprintKey a) where
 --
 {-# NOINLINE memoFingerprint #-}
 memoFingerprint
-   :: (Show a, Typeable a) => MemoFingerprintKey a -> GenHaxl u a -> GenHaxl u a
+  :: Typeable a => MemoFingerprintKey a -> GenHaxl u a -> GenHaxl u a
 memoFingerprint key = cachedComputation key
diff --git a/Haxl/Core/Monad.hs b/Haxl/Core/Monad.hs
index 2a7f3fd..63921e4 100644
--- a/Haxl/Core/Monad.hs
+++ b/Haxl/Core/Monad.hs
@@ -725,7 +725,7 @@ runHaxl).
 --
 cachedComputation
    :: forall req u a.
-      (Eq (req a)
+      ( Eq (req a)
       , Hashable (req a)
       , Typeable (req a))
    => req a -> GenHaxl u a -> GenHaxl u a