Invert module-dep between Control.Monad and Data.Foldable

This is the last preparation needed before generalizing entities in
Control.Monad conflicting with those from Data.Foldable (re #9586)

Reviewed By: ekmett, austin

Differential Revision: https://phabricator.haskell.org/D225

2 files changed, 5 insertions, 0 deletions

diff --git a/libraries/base/Control/Applicative.hs b/libraries/base/Control/Applicative.hs
index accf58f561..d6157b3d69 100644
--- a/libraries/base/Control/Applicative.hs
+++ b/libraries/base/Control/Applicative.hs
@@ -53,6 +53,7 @@ import Data.Maybe
 import Data.Tuple
 import Data.Eq
 import Data.Ord
+import Data.Foldable (Foldable(..))
 import Data.Functor ((<$>))
 
 import GHC.Base hiding ((.), id)
@@ -64,6 +65,9 @@ import GHC.Show (Show)
 newtype Const a b = Const { getConst :: a }
                   deriving (Generic, Generic1)
 
+instance Foldable (Const m) where
+    foldMap _ _ = mempty
+
 instance Functor (Const m) where
     fmap _ (Const v) = Const v
 
diff --git a/libraries/base/Control/Monad.hs b/libraries/base/Control/Monad.hs
index 0597055da9..3487a09c65 100644
--- a/libraries/base/Control/Monad.hs
+++ b/libraries/base/Control/Monad.hs
@@ -76,6 +76,7 @@ module Control.Monad
     , (<$!>)
     ) where
 
+import Data.Foldable ()
 import Data.Functor ( void )
 import Data.Maybe