base: Add missing instances for Data.Ord.Down

Specifically:

 * MonadFix
 * MonadZip
 * Data
 * Foldable
 * Traversable
 * Eq1
 * Ord1
 * Read1
 * Show1
 * Generic
 * Generic1

Fixes #15098.

Reviewers: RyanGlScott, hvr

Reviewed By: RyanGlScott

Subscribers: sjakobi, rwbarton, thomie, ekmett, carter

GHC Trac Issues: #15098

Differential Revision: https://phabricator.haskell.org/D4870

2 files changed, 15 insertions, 0 deletions

diff --git a/libraries/base/Control/Monad/Fix.hs b/libraries/base/Control/Monad/Fix.hs
index 4c333c32ed..bb269847b6 100644
--- a/libraries/base/Control/Monad/Fix.hs
+++ b/libraries/base/Control/Monad/Fix.hs
@@ -29,6 +29,7 @@ import Data.Function ( fix )
 import Data.Maybe
 import Data.Monoid ( Dual(..), Sum(..), Product(..)
                    , First(..), Last(..), Alt(..), Ap(..) )
+import Data.Ord ( Down(..) )
 import GHC.Base ( Monad, NonEmpty(..), errorWithoutStackTrace, (.) )
 import GHC.Generics
 import GHC.List ( head, tail )
@@ -149,3 +150,10 @@ instance (MonadFix f, MonadFix g) => MonadFix (f :*: g) where
       where
         fstP (a :*: _) = a
         sndP (_ :*: b) = b
+
+-- Instances for Data.Ord
+
+-- | @since 4.12.0.0
+instance MonadFix Down where
+    mfix f = Down (fix (getDown . f))
+      where getDown (Down x) = x
diff --git a/libraries/base/Control/Monad/Zip.hs b/libraries/base/Control/Monad/Zip.hs
index d484d1fa83..beef913119 100644
--- a/libraries/base/Control/Monad/Zip.hs
+++ b/libraries/base/Control/Monad/Zip.hs
@@ -21,6 +21,7 @@ module Control.Monad.Zip where
 import Control.Monad (liftM, liftM2)
 import Data.Functor.Identity
 import Data.Monoid
+import Data.Ord ( Down(..) )
 import Data.Proxy
 import qualified Data.List.NonEmpty as NE
 import GHC.Generics
@@ -124,3 +125,9 @@ instance MonadZip f => MonadZip (M1 i c f) where
 -- | @since 4.9.0.0
 instance (MonadZip f, MonadZip g) => MonadZip (f :*: g) where
     mzipWith f (x1 :*: y1) (x2 :*: y2) = mzipWith f x1 x2 :*: mzipWith f y1 y2
+
+-- instances for Data.Ord
+
+-- | @since 4.12.0.0
+instance MonadZip Down where
+    mzipWith = liftM2