Use DeriveFunctor throughout the codebase (#15654)

2 files changed, 6 insertions, 9 deletions

diff --git a/compiler/stgSyn/CoreToStg.hs b/compiler/stgSyn/CoreToStg.hs
index 12766e90d4..3187298425 100644
--- a/compiler/stgSyn/CoreToStg.hs
+++ b/compiler/stgSyn/CoreToStg.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP #-}
+{-# LANGUAGE CPP, DeriveFunctor #-}
 
 --
 -- (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
@@ -50,7 +50,7 @@ import SrcLoc           ( mkGeneralSrcSpan )
 
 import Data.List.NonEmpty (nonEmpty, toList)
 import Data.Maybe    (fromMaybe)
-import Control.Monad (liftM, ap)
+import Control.Monad (ap)
 
 -- Note [Live vs free]
 -- ~~~~~~~~~~~~~~~~~~~
@@ -813,6 +813,7 @@ newtype CtsM a = CtsM
     { unCtsM :: IdEnv HowBound
              -> a
     }
+    deriving (Functor)
 
 data HowBound
   = ImportBound         -- Used only as a response to lookupBinding; never
@@ -861,9 +862,6 @@ thenCts :: CtsM a -> (a -> CtsM b) -> CtsM b
 thenCts m k = CtsM $ \env
   -> unCtsM (k (unCtsM m env)) env
 
-instance Functor CtsM where
-    fmap = liftM
-
 instance Applicative CtsM where
     pure = returnCts
     (<*>) = ap
diff --git a/compiler/stgSyn/StgLint.hs b/compiler/stgSyn/StgLint.hs
index c949f348f1..f83b44859c 100644
--- a/compiler/stgSyn/StgLint.hs
+++ b/compiler/stgSyn/StgLint.hs
@@ -32,7 +32,8 @@ Since then there were some attempts at enabling it again, as summarised in
 basic properties listed above.
 -}
 
-{-# LANGUAGE ScopedTypeVariables, FlexibleContexts, TypeFamilies #-}
+{-# LANGUAGE ScopedTypeVariables, FlexibleContexts, TypeFamilies,
+  DeriveFunctor #-}
 
 module StgLint ( lintStgTopBindings ) where
 
@@ -258,6 +259,7 @@ newtype LintM a = LintM
               -> Bag MsgDoc        -- Error messages so far
               -> (a, Bag MsgDoc)   -- Result and error messages (if any)
     }
+    deriving (Functor)
 
 data LintFlags = LintFlags { lf_unarised :: !Bool
                              -- ^ have we run the unariser yet?
@@ -293,9 +295,6 @@ initL this_mod unarised locals (LintM m) = do
   else
       Just (vcat (punctuate blankLine (bagToList errs)))
 
-instance Functor LintM where
-      fmap = liftM
-
 instance Applicative LintM where
       pure a = LintM $ \_mod _lf _loc _scope errs -> (a, errs)
       (<*>) = ap