From 4a76ecedccd80f16eca38be05b256bcedd3d6b65 Mon Sep 17 00:00:00 2001
From: Michael Walker <mike@barrucadu.co.uk>
Date: Fri, 14 Aug 2015 15:20:03 +0100
Subject: [PATCH] Add Applicative constraint to classes for pre-AMP GHC

---
 Control/Monad/Conc/Class.hs | 4 +++-
 Control/Monad/STM/Class.hs  | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/Control/Monad/Conc/Class.hs b/Control/Monad/Conc/Class.hs
index 8a77891..c43feac 100755
--- a/Control/Monad/Conc/Class.hs
+++ b/Control/Monad/Conc/Class.hs
@@ -12,6 +12,7 @@ module Control.Monad.Conc.Class
   , killThread
   ) where
 
+import Control.Applicative (Applicative)
 import Control.Concurrent (forkIO)
 import Control.Concurrent.MVar (MVar, readMVar, newEmptyMVar, putMVar, tryPutMVar, takeMVar, tryTakeMVar)
 import Control.Exception (Exception, AsyncException(ThreadKilled), SomeException)
@@ -51,7 +52,8 @@ import qualified Control.Monad.Writer.Strict as WS
 --
 -- Every @MonadConc@ has an associated 'MonadSTM', transactions of
 -- which can be run atomically.
-class ( Monad m, MonadCatch m, MonadThrow m, MonadMask m
+class ( Applicative m, Monad m
+      , MonadCatch m, MonadThrow m, MonadMask m
       , MonadSTM (STMLike m)
       , Eq (ThreadId m), Show (ThreadId m)) => MonadConc m  where
   -- | The associated 'MonadSTM' for this class.
diff --git a/Control/Monad/STM/Class.hs b/Control/Monad/STM/Class.hs
index 01a50c3..ac4790a 100755
--- a/Control/Monad/STM/Class.hs
+++ b/Control/Monad/STM/Class.hs
@@ -4,6 +4,7 @@
 -- with 'MonadConc'.
 module Control.Monad.STM.Class where
 
+import Control.Applicative (Applicative)
 import Control.Concurrent.STM (STM)
 import Control.Concurrent.STM.TVar (TVar, newTVar, readTVar, writeTVar)
 import Control.Exception (Exception)
@@ -30,7 +31,7 @@ import qualified Control.Monad.Writer.Strict as WS
 --
 -- A minimal implementation consists of 'retry', 'orElse', 'newCTVar',
 -- 'readCTVar', and 'writeCTVar'.
-class (Monad m, MonadCatch m, MonadThrow m) => MonadSTM m where
+class (Applicative m, Monad m, MonadCatch m, MonadThrow m) => MonadSTM m where
   -- | The mutable reference type. These behave like 'TVar's, in that
   -- they always contain a value and updates are non-blocking and
   -- synchronised.