Use DeriveFunctor throughout the codebase (#15654)

6 files changed, 15 insertions, 29 deletions

diff --git a/compiler/typecheck/TcCanonical.hs b/compiler/typecheck/TcCanonical.hs
index 9440d5ff0a..e0c87e0f70 100644
--- a/compiler/typecheck/TcCanonical.hs
+++ b/compiler/typecheck/TcCanonical.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveFunctor #-}
 
 module TcCanonical(
      canonicalize,
@@ -2188,10 +2189,7 @@ data StopOrContinue a
   | Stop CtEvidence   -- The (rewritten) constraint was solved
          SDoc         -- Tells how it was solved
                       -- Any new sub-goals have been put on the work list
-
-instance Functor StopOrContinue where
-  fmap f (ContinueWith x) = ContinueWith (f x)
-  fmap _ (Stop ev s)      = Stop ev s
+  deriving (Functor)
 
 instance Outputable a => Outputable (StopOrContinue a) where
   ppr (Stop ev s)      = text "Stop" <> parens s <+> ppr ev
diff --git a/compiler/typecheck/TcFlatten.hs b/compiler/typecheck/TcFlatten.hs
index 39a33f3fd7..2bb3d1c0e8 100644
--- a/compiler/typecheck/TcFlatten.hs
+++ b/compiler/typecheck/TcFlatten.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, ViewPatterns, BangPatterns #-}
+{-# LANGUAGE CPP, DeriveFunctor, ViewPatterns, BangPatterns #-}
 
 module TcFlatten(
    FlattenMode(..),
@@ -485,15 +485,13 @@ eqFlattenMode _  _ = False
 -- See Note [The flattening work list].
 newtype FlatM a
   = FlatM { runFlatM :: FlattenEnv -> TcS a }
+  deriving (Functor)
 
 instance Monad FlatM where
   m >>= k  = FlatM $ \env ->
              do { a  <- runFlatM m env
                 ; runFlatM (k a) env }
 
-instance Functor FlatM where
-  fmap = liftM
-
 instance Applicative FlatM where
   pure x = FlatM $ const (pure x)
   (<*>) = ap
diff --git a/compiler/typecheck/TcRnTypes.hs b/compiler/typecheck/TcRnTypes.hs
index bf98e0c2b1..221d9cea8c 100644
--- a/compiler/typecheck/TcRnTypes.hs
+++ b/compiler/typecheck/TcRnTypes.hs
@@ -16,7 +16,7 @@ For state that is global and should be returned at the end (e.g not part
 of the stack mechanism), you should use a TcRef (= IORef) to store them.
 -}
 
-{-# LANGUAGE CPP, ExistentialQuantification, GeneralizedNewtypeDeriving,
+{-# LANGUAGE CPP, DeriveFunctor, ExistentialQuantification, GeneralizedNewtypeDeriving,
              ViewPatterns #-}
 
 module TcRnTypes(
@@ -195,7 +195,7 @@ import Util
 import PrelNames ( isUnboundName )
 import CostCentreState
 
-import Control.Monad (ap, liftM, msum)
+import Control.Monad (ap, msum)
 import qualified Control.Monad.Fail as MonadFail
 import Data.Set      ( Set )
 import qualified Data.Set as S
@@ -3832,10 +3832,7 @@ type TcPluginSolver = [Ct]    -- given
                    -> [Ct]    -- wanted
                    -> TcPluginM TcPluginResult
 
-newtype TcPluginM a = TcPluginM (EvBindsVar -> TcM a)
-
-instance Functor TcPluginM where
-  fmap = liftM
+newtype TcPluginM a = TcPluginM (EvBindsVar -> TcM a) deriving (Functor)
 
 instance Applicative TcPluginM where
   pure x = TcPluginM (const $ pure x)
diff --git a/compiler/typecheck/TcSMonad.hs b/compiler/typecheck/TcSMonad.hs
index 8d98a17149..68496dfca6 100644
--- a/compiler/typecheck/TcSMonad.hs
+++ b/compiler/typecheck/TcSMonad.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, TypeFamilies #-}
+{-# LANGUAGE CPP, DeriveFunctor, TypeFamilies #-}
 
 -- Type definitions for the constraint solver
 module TcSMonad (
@@ -2601,10 +2601,7 @@ data TcSEnv
     }
 
 ---------------
-newtype TcS a = TcS { unTcS :: TcSEnv -> TcM a }
-
-instance Functor TcS where
-  fmap f m = TcS $ fmap f . unTcS m
+newtype TcS a = TcS { unTcS :: TcSEnv -> TcM a } deriving (Functor)
 
 instance Applicative TcS where
   pure x = TcS (\_ -> return x)
diff --git a/compiler/typecheck/TcTyDecls.hs b/compiler/typecheck/TcTyDecls.hs
index 205771b2db..7a68fe1144 100644
--- a/compiler/typecheck/TcTyDecls.hs
+++ b/compiler/typecheck/TcTyDecls.hs
@@ -10,6 +10,7 @@ files for imported data types.
 -}
 
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE ViewPatterns #-}
 
@@ -149,12 +150,10 @@ synonymTyConsOfType ty
 -- a failure message reporting that a cycle was found.
 newtype SynCycleM a = SynCycleM {
     runSynCycleM :: SynCycleState -> Either (SrcSpan, SDoc) (a, SynCycleState) }
+    deriving (Functor)
 
 type SynCycleState = NameSet
 
-instance Functor SynCycleM where
-    fmap = liftM
-
 instance Applicative SynCycleM where
     pure x = SynCycleM $ \state -> Right (x, state)
     (<*>) = ap
@@ -677,9 +676,7 @@ newtype RoleM a = RM { unRM :: Maybe Name -- of the tycon
                             -> Int          -- size of VarPositions
                             -> RoleInferenceState
                             -> (a, RoleInferenceState) }
-
-instance Functor RoleM where
-    fmap = liftM
+    deriving (Functor)
 
 instance Applicative RoleM where
     pure x = RM $ \_ _ _ state -> (x, state)
diff --git a/compiler/typecheck/TcUnify.hs b/compiler/typecheck/TcUnify.hs
index cbf98d888c..078ebecd54 100644
--- a/compiler/typecheck/TcUnify.hs
+++ b/compiler/typecheck/TcUnify.hs
@@ -6,7 +6,8 @@
 Type subsumption and unification
 -}
 
-{-# LANGUAGE CPP, MultiWayIf, TupleSections, ScopedTypeVariables #-}
+{-# LANGUAGE CPP, DeriveFunctor, MultiWayIf, TupleSections,
+    ScopedTypeVariables #-}
 
 module TcUnify (
   -- Full-blown subsumption
@@ -2119,9 +2120,7 @@ data MetaTyVarUpdateResult a
   = MTVU_OK a
   | MTVU_Bad     -- Forall, predicate, or type family
   | MTVU_Occurs
-
-instance Functor MetaTyVarUpdateResult where
-      fmap = liftM
+    deriving (Functor)
 
 instance Applicative MetaTyVarUpdateResult where
       pure = MTVU_OK