Prepare for liftA2 being exposed in the Prelude

Use a private `Prelude` temporarily to deal with warnings arising
from the fact that `liftA2` hasn't always been exposed in the
`Prelude`. Other approaches seemed to involve too much CPP or
required disabling redundant import warnings, which we really don't
want.

Author: treeowl

containers-tests/containers-tests.cabal

@@ -109,6 +109,7 @@ library
       Utils.NoThunks
 
   other-modules:
+    Prelude
     Utils.Containers.Internal.Coercions
     Utils.Containers.Internal.PtrEquality
     Utils.Containers.Internal.State

containers/containers.cabal

@@ -71,6 +71,7 @@ Library
         Utils.Containers.Internal.StrictPair
 
     other-modules:
+        Prelude
         Utils.Containers.Internal.State
         Utils.Containers.Internal.StrictMaybe
         Utils.Containers.Internal.PtrEquality

containers/src/Data/Graph.hs

@@ -107,7 +107,6 @@ import qualified Data.IntSet as Set
 import Data.Tree (Tree(Node), Forest)
 
 -- std interfaces
-import Control.Applicative
 import Data.Foldable as F
 import Control.DeepSeq (NFData(rnf))
 import Data.Maybe

containers/src/Data/IntMap/Internal.hs

@@ -294,7 +294,6 @@ module Data.IntMap.Internal (
     ) where
 
 import Data.Functor.Identity (Identity (..))
-import Control.Applicative (liftA2)
 import Data.Semigroup (Semigroup(stimes))
 #if !(MIN_VERSION_base(4,11,0))
 import Data.Semigroup (Semigroup((<>)))

containers/src/Data/IntMap/Strict/Internal.hs

@@ -345,7 +345,6 @@ import Data.IntMap.Internal.DeprecatedDebug (showTree, showTreeWith)
 import qualified Data.IntSet.Internal as IntSet
 import Utils.Containers.Internal.BitUtil
 import Utils.Containers.Internal.StrictPair
-import Control.Applicative (Applicative (..), liftA2)
 import qualified Data.Foldable as Foldable
 
 {--------------------------------------------------------------------

containers/src/Data/Sequence.hs

@@ -250,7 +250,6 @@ import Data.Sequence.Internal.Sorting
 import Prelude ()
 #ifdef __HADDOCK_VERSION__
 import Control.Monad (Monad (..))
-import Control.Applicative (Applicative (..))
 import Data.Functor (Functor (..))
 #endif
 

containers/src/Data/Sequence/Internal.hs

@@ -199,12 +199,12 @@ import Prelude hiding (
 #if MIN_VERSION_base(4,11,0)
     (<>),
 #endif
-    Applicative, (<$>), foldMap, Monoid,
+    (<$>), foldMap, Monoid,
     null, length, lookup, take, drop, splitAt, foldl, foldl1, foldr, foldr1,
     scanl, scanl1, scanr, scanr1, replicate, zip, zipWith, zip3, zipWith3,
     unzip, takeWhile, dropWhile, iterate, reverse, filter, mapM, sum, all)
-import Control.Applicative (Applicative(..), (<$>), (<**>),  Alternative,
-                            liftA2, liftA3)
+import Control.Applicative ((<$>), (<**>),  Alternative,
+                            liftA3)
 import qualified Control.Applicative as Applicative
 import Control.DeepSeq (NFData(rnf))
 import Control.Monad (MonadPlus(..))

containers/src/Data/Tree.hs

@@ -53,7 +53,6 @@ module Data.Tree(
     ) where
 
 import Data.Foldable (toList)
-import Control.Applicative (Applicative(..), liftA2)
 import Control.Monad (liftM)
 import Control.Monad.Fix (MonadFix (..), fix)
 import Data.Sequence (Seq, empty, singleton, (<|), (|>), fromList,

containers/src/Prelude.hs

@@ -0,0 +1,21 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE PackageImports #-}
+-- | This hideous module lets us avoid dealing with the fact that
+-- @liftA2@ wasn't previously exported from the standard prelude.
+module Prelude
+  ( module Prel
+  , Applicative (..)
+#if !MIN_VERSION_base(4,10,0)
+  , liftA2
+#endif
+  )
+  where
+
+import "base" Prelude as Prel
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative(Applicative(..))
+#endif
+
+#if !MIN_VERSION_base(4,10,0)
+import Control.Applicative(liftA2)
+#endif

containers/src/Utils/Containers/Internal/State.hs

@@ -6,7 +6,7 @@
 module Utils.Containers.Internal.State where
 
 import Control.Monad (ap, liftM2)
-import Control.Applicative (Applicative(..), liftA)
+import Control.Applicative (liftA)
 
 newtype State s a = State {runState :: s -> (s, a)}