3 files changed, 10 insertions, 18 deletions
diff --git a/compiler/cmm/CmmLint.hs b/compiler/cmm/CmmLint.hs
index 3224bb8cab..d5c3f84443 100644
--- a/compiler/cmm/CmmLint.hs
+++ b/compiler/cmm/CmmLint.hs
@@ -5,6 +5,7 @@
 -- CmmLint: checking the correctness of Cmm statements and expressions
 --
 -----------------------------------------------------------------------------
+{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE GADTs #-}
 module CmmLint (
     cmmLint, cmmLintGraph
@@ -24,7 +25,7 @@ import PprCmm ()
 import Outputable
 import DynFlags
 
-import Control.Monad (liftM, ap)
+import Control.Monad (ap)
 
 -- Things to check:
 --     - invariant on CmmBlock in CmmExpr (see comment there)
@@ -212,9 +213,7 @@ checkCond _ expr
 -- just a basic error monad:
 
 newtype CmmLint a = CmmLint { unCL :: DynFlags -> Either SDoc a }
-
-instance Functor CmmLint where
-      fmap = liftM
+    deriving (Functor)
 
 instance Applicative CmmLint where
       pure a = CmmLint (\_ -> Right a)
diff --git a/compiler/cmm/Hoopl/Block.hs b/compiler/cmm/Hoopl/Block.hs
index c4ff1794e8..5c31932934 100644
--- a/compiler/cmm/Hoopl/Block.hs
+++ b/compiler/cmm/Hoopl/Block.hs
@@ -1,7 +1,9 @@
+{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE StandaloneDeriving #-}
 module Hoopl.Block
     ( C
     , O
@@ -64,14 +66,8 @@ data MaybeC ex t where
   JustC    :: t -> MaybeC C t
   NothingC ::      MaybeC O t
 
-
-instance Functor (MaybeO ex) where
-  fmap _ NothingO = NothingO
-  fmap f (JustO a) = JustO (f a)
-
-instance Functor (MaybeC ex) where
-  fmap _ NothingC = NothingC
-  fmap f (JustC a) = JustC (f a)
+deriving instance Functor (MaybeO ex)
+deriving instance Functor (MaybeC ex)
 
 -- -----------------------------------------------------------------------------
 -- The Block type
diff --git a/compiler/cmm/PprC.hs b/compiler/cmm/PprC.hs
index 822de431a4..2038801de3 100644
--- a/compiler/cmm/PprC.hs
+++ b/compiler/cmm/PprC.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, GADTs #-}
+{-# LANGUAGE CPP, DeriveFunctor, GADTs, PatternSynonyms #-}
 
 -----------------------------------------------------------------------------
 --
@@ -61,7 +61,7 @@ import Data.Map (Map)
 import Data.Word
 import System.IO
 import qualified Data.Map as Map
-import Control.Monad (liftM, ap)
+import Control.Monad (ap)
 import qualified Data.Array.Unsafe as U ( castSTUArray )
 import Data.Array.ST
 
@@ -1078,10 +1078,7 @@ pprExternDecl lbl
         <> semi
 
 type TEState = (UniqSet LocalReg, Map CLabel ())
-newtype TE a = TE { unTE :: TEState -> (a, TEState) }
-
-instance Functor TE where
-      fmap = liftM
+newtype TE a = TE { unTE :: TEState -> (a, TEState) } deriving (Functor)
 
 instance Applicative TE where
       pure a = TE $ \s -> (a, s)