Revert "More instances that are now possible"

This reverts commit d4cfb0e.

src/Control/Lens/Indexed.hs

@@ -672,31 +672,6 @@ instance (Eq k, Hashable k) => TraversableWithIndex k (HashMap k) where
   itraverse = HashMap.traverseWithKey
   {-# INLINE itraverse #-}
 
-instance FunctorWithIndex i (Accessor r) where
-  imap _ = Accessor . runAccessor
-  {-# INLINE imap #-}
-
-instance FoldableWithIndex i (Accessor r) where
-  ifoldMap _ = mempty . runAccessor
-  {-# INLINE ifoldMap #-}
-
-instance TraversableWithIndex i (Accessor r) where
-  itraverse _ = pure . Accessor . runAccessor
-  {-# INLINE itraverse #-}
-
-
-instance FunctorWithIndex i (Const r) where
-  imap _ = Const . getConst
-  {-# INLINE imap #-}
-
-instance FoldableWithIndex i (Const r) where
-  ifoldMap _ = mempty . getConst
-  {-# INLINE ifoldMap #-}
-
-instance TraversableWithIndex i (Const r) where
-  itraverse _ = pure . Const . getConst
-  {-# INLINE itraverse #-}
-
 instance FunctorWithIndex r ((->) r) where
   imap f g x = f x (g x)
   {-# INLINE imap #-}

src/Control/Lens/Internal/Getter.hs

@@ -21,11 +21,9 @@ module Control.Lens.Internal.Getter
   ) where
 
 import Control.Applicative
-import Data.Foldable
 import Data.Functor.Apply
 import Data.Functor.Contravariant
 import Data.Semigroup
-import Data.Traversable
 import Data.Void
 
 -- | This class is provided mostly for backwards compatibility with lens 3.8,
@@ -68,17 +66,9 @@ noEffect = coerce $ pure ()
 newtype Accessor r a = Accessor { runAccessor :: r }
 
 instance Functor (Accessor r) where
-  fmap _ = Accessor . runAccessor
+  fmap _ (Accessor m) = Accessor m
   {-# INLINE fmap #-}
 
-instance Foldable (Accessor r) where
-  foldMap _ _ = mempty
-  {-# INLINE foldMap #-}
-
-instance Traversable (Accessor r) where
-  traverse _ = pure . Accessor . runAccessor
-  {-# INLINE traverse #-}
-
 instance Contravariant (Accessor r) where
   contramap _ (Accessor m) = Accessor m
   {-# INLINE contramap #-}