Export `Monoid(..)`/`Foldable(..)`/`Traversable(..)` from Prelude

This finally exposes also the methods of these 3 classes in the Prelude
in order to allow to define basic class instances w/o needing imports.

This almost completes the primary goal of #9586

NOTE: `fold`, `foldl'`, `foldr'`, and `toList` are not exposed yet,
      as they require upstream fixes for at least `containers` and
      `bytestring`, and are not required for defining basic instances.

Reviewed By: ekmett, austin

Differential Revision: https://phabricator.haskell.org/D236

2 files changed, 10 insertions, 3 deletions

diff --git a/compiler/utils/Pair.lhs b/compiler/utils/Pair.lhs
index ca7c2a7f8e..529ba669ea 100644
--- a/compiler/utils/Pair.lhs
+++ b/compiler/utils/Pair.lhs
@@ -10,10 +10,12 @@ module Pair ( Pair(..), unPair, toPair, swap ) where
 #include "HsVersions.h"
 
 import Outputable
-import Data.Monoid
 import Control.Applicative
+#if __GLASGOW_HASKELL__ < 709
 import Data.Foldable
+import Data.Monoid
 import Data.Traversable
+#endif
 
 data Pair a = Pair { pFst :: a, pSnd :: a }
 -- Note that Pair is a *unary* type constructor
@@ -46,4 +48,4 @@ toPair (x,y) = Pair x y
 
 swap :: Pair a -> Pair a
 swap (Pair x y) = Pair y x
-\end{code}
\ No newline at end of file
+\end{code}
diff --git a/compiler/utils/UniqFM.lhs b/compiler/utils/UniqFM.lhs
index d8e08f599a..c941ce8884 100644
--- a/compiler/utils/UniqFM.lhs
+++ b/compiler/utils/UniqFM.lhs
@@ -20,7 +20,10 @@ and ``addToUFM\_C'' and ``Data.IntMap.insertWith'' differ in the order
 of arguments of combining function.
 
 \begin{code}
-{-# LANGUAGE DeriveTraversable, DeriveDataTypeable, GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveTraversable #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# OPTIONS_GHC -Wall #-}
 
 module UniqFM (
@@ -76,7 +79,9 @@ import qualified Data.Foldable as Foldable
 import qualified Data.Traversable as Traversable
 import Data.Typeable
 import Data.Data
+#if __GLASGOW_HASKELL__ < 709
 import Data.Monoid
+#endif
 \end{code}
 
 %************************************************************************