Add moral Functor constraint for to and friends

src/Control/Lens/Getter.hs

@@ -16,6 +16,13 @@
 {-# LANGUAGE NoPolyKinds #-}
 {-# LANGUAGE NoDataKinds #-}
 #endif
+
+-- Disable the warnings generated by 'to', 'ito', 'like', 'ilike'.
+-- These functions are intended to produce 'Getters'. Without this constraint
+-- users would get warnings when annotating types at uses of these functions.
+#if __GLASGOW_HASKELL__ >= 711
+{-# OPTIONS_GHC -fno-warn-redundant-constraints #-}
+#endif
 -------------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Getter
@@ -137,15 +144,15 @@ infixl 8 ^., ^@.
 -- @
 -- 'to' :: (s -> a) -> 'IndexPreservingGetter' s a
 -- @
-to :: (Profunctor p, Contravariant f) => (s -> a) -> Optic' p f s a
+to :: (Profunctor p, Contravariant f, Functor f) => (s -> a) -> Optic' p f s a
 to k = dimap k (contramap k)
 {-# INLINE to #-}
 
 -- |
 -- @
 -- 'ito' :: (s -> (i, a)) -> 'IndexedGetter' i s a
 -- @
-ito :: (Indexable i p, Contravariant f) => (s -> (i, a)) -> Over' p f s a
+ito :: (Indexable i p, Contravariant f, Functor f) => (s -> (i, a)) -> Over' p f s a
 ito k = dimap k (contramap (snd . k)) . uncurry . indexed
 {-# INLINE ito #-}
 
@@ -164,15 +171,15 @@ ito k = dimap k (contramap (snd . k)) . uncurry . indexed
 -- @
 -- 'like' :: a -> 'IndexPreservingGetter' s a
 -- @
-like :: (Profunctor p, Contravariant f) => a -> Optic' p f s a
+like :: (Profunctor p, Contravariant f, Functor f) => a -> Optic' p f s a
 like a = to (const a)
 {-# INLINE like #-}
 
 -- |
 -- @
 -- 'ilike' :: i -> a -> 'IndexedGetter' i s a
 -- @
-ilike :: (Indexable i p, Contravariant f) => i -> a -> Over' p f s a
+ilike :: (Indexable i p, Contravariant f, Functor f) => i -> a -> Over' p f s a
 ilike i a = ito (const (i, a))
 {-# INLINE ilike #-}
 

src/Control/Lens/Review.hs

@@ -108,7 +108,7 @@ un = unto . view
 -- 're' :: 'Prism' s t a b -> 'Getter' b t
 -- 're' :: 'Iso' s t a b   -> 'Getter' b t
 -- @
-re :: Contravariant f => AReview t b -> LensLike' f b t
+re :: AReview t b -> Getter b t
 re p = to (runIdentity #. unTagged #. p .# Tagged .# Identity)
 {-# INLINE re #-}