2 files changed, 5 insertions, 7 deletions
diff --git a/compiler/simplCore/CoreMonad.hs b/compiler/simplCore/CoreMonad.hs
index 3a2277a7a7..29e4b00c4d 100644
--- a/compiler/simplCore/CoreMonad.hs
+++ b/compiler/simplCore/CoreMonad.hs
@@ -5,6 +5,7 @@
 -}
 
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveFunctor #-}
 
 module CoreMonad (
     -- * Configuration of the core-to-core passes
@@ -582,9 +583,7 @@ type CoreIOEnv = IOEnv CoreReader
 -- | The monad used by Core-to-Core passes to access common state, register simplification
 -- statistics and so on
 newtype CoreM a = CoreM { unCoreM :: CoreState -> CoreIOEnv (a, CoreState, CoreWriter) }
-
-instance Functor CoreM where
-    fmap = liftM
+    deriving (Functor)
 
 instance Monad CoreM where
     mx >>= f = CoreM $ \s -> do
diff --git a/compiler/simplCore/SimplMonad.hs b/compiler/simplCore/SimplMonad.hs
index c28f99f9dd..732805e9ee 100644
--- a/compiler/simplCore/SimplMonad.hs
+++ b/compiler/simplCore/SimplMonad.hs
@@ -4,6 +4,7 @@
 \section[SimplMonad]{The simplifier Monad}
 -}
 
+{-# LANGUAGE DeriveFunctor #-}
 module SimplMonad (
         -- The monad
         SimplM,
@@ -37,7 +38,7 @@ import MonadUtils
 import ErrUtils as Err
 import Panic (throwGhcExceptionIO, GhcException (..))
 import BasicTypes          ( IntWithInf, treatZeroAsInf, mkIntWithInf )
-import Control.Monad       ( liftM, ap )
+import Control.Monad       ( ap )
 
 {-
 ************************************************************************
@@ -57,6 +58,7 @@ newtype SimplM result
                 -> SimplCount
                 -> IO (result, UniqSupply, SimplCount)}
   -- we only need IO here for dump output
+    deriving (Functor)
 
 data SimplTopEnv
   = STE { st_flags     :: DynFlags
@@ -104,9 +106,6 @@ computeMaxTicks dflags size
 {-# INLINE returnSmpl #-}
 
 
-instance Functor SimplM where
-    fmap = liftM
-
 instance Applicative SimplM where
     pure  = returnSmpl
     (<*>) = ap