Move `Maybe`-typedef into GHC.Base

This is preparatory work for reintroducing SPECIALISEs that were lost
in d94de87252d0fe2ae97341d186b03a2fbe136b04

Differential Revision: https://phabricator.haskell.org/D214

31 files changed, 57 insertions, 78 deletions

diff --git a/libraries/base/Control/Exception.hs b/libraries/base/Control/Exception.hs
index 7c019eb5ca..252597d70e 100644
--- a/libraries/base/Control/Exception.hs
+++ b/libraries/base/Control/Exception.hs
@@ -133,7 +133,6 @@ import Control.Exception.Base
 
 import GHC.Base
 import GHC.IO (unsafeUnmask)
-import Data.Maybe
 
 -- | You need this when using 'catches'.
 data Handler a = forall e . Exception e => Handler (e -> IO a)
diff --git a/libraries/base/Control/Exception/Base.hs b/libraries/base/Control/Exception/Base.hs
index 8df4958cbb..afb715193b 100644
--- a/libraries/base/Control/Exception/Base.hs
+++ b/libraries/base/Control/Exception/Base.hs
@@ -105,7 +105,6 @@ import GHC.Conc.Sync
 
 import Data.Dynamic
 import Data.Either
-import Data.Maybe
 
 -----------------------------------------------------------------------------
 -- Catching exceptions
diff --git a/libraries/base/Data/Maybe.hs b/libraries/base/Data/Maybe.hs
index de8eadcd6e..5923ae1061 100644
--- a/libraries/base/Data/Maybe.hs
+++ b/libraries/base/Data/Maybe.hs
@@ -34,52 +34,6 @@ module Data.Maybe
 import GHC.Base
 
 -- ---------------------------------------------------------------------------
--- The Maybe type, and instances
-
--- | The 'Maybe' type encapsulates an optional value.  A value of type
--- @'Maybe' a@ either contains a value of type @a@ (represented as @'Just' a@), 
--- or it is empty (represented as 'Nothing').  Using 'Maybe' is a good way to 
--- deal with errors or exceptional cases without resorting to drastic
--- measures such as 'error'.
---
--- The 'Maybe' type is also a monad.  It is a simple kind of error
--- monad, where all errors are represented by 'Nothing'.  A richer
--- error monad can be built using the 'Data.Either.Either' type.
-
-data  Maybe a  =  Nothing | Just a
-  deriving (Eq, Ord)
-
--- | Lift a semigroup into 'Maybe' forming a 'Monoid' according to
--- <http://en.wikipedia.org/wiki/Monoid>: \"Any semigroup @S@ may be
--- turned into a monoid simply by adjoining an element @e@ not in @S@
--- and defining @e*e = e@ and @e*s = s = s*e@ for all @s ∈ S@.\" Since
--- there is no \"Semigroup\" typeclass providing just 'mappend', we
--- use 'Monoid' instead.
-instance Monoid a => Monoid (Maybe a) where
-  mempty = Nothing
-  Nothing `mappend` m = m
-  m `mappend` Nothing = m
-  Just m1 `mappend` Just m2 = Just (m1 `mappend` m2)
-
-instance  Functor Maybe  where
-    fmap _ Nothing       = Nothing
-    fmap f (Just a)      = Just (f a)
-
-instance Applicative Maybe where
-    pure = return
-    (<*>) = ap
-
-instance  Monad Maybe  where
-    (Just x) >>= k      = k x
-    Nothing  >>= _      = Nothing
-
-    (Just _) >>  k      = k
-    Nothing  >>  _      = Nothing
-
-    return              = Just
-    fail _              = Nothing
-
--- ---------------------------------------------------------------------------
 -- Functions over Maybe
 
 -- | The 'maybe' function takes a default value, a function, and a 'Maybe'
diff --git a/libraries/base/Data/Monoid.hs b/libraries/base/Data/Monoid.hs
index 6b393b173e..8b8c8e80b7 100644
--- a/libraries/base/Data/Monoid.hs
+++ b/libraries/base/Data/Monoid.hs
@@ -46,7 +46,6 @@ import GHC.Num
 import GHC.Read
 import GHC.Show
 import GHC.Generics
-import Data.Maybe
 
 {-
 -- just for testing
diff --git a/libraries/base/Data/OldTypeable/Internal.hs b/libraries/base/Data/OldTypeable/Internal.hs
index 2b02930466..d5e39c5688 100644
--- a/libraries/base/Data/OldTypeable/Internal.hs
+++ b/libraries/base/Data/OldTypeable/Internal.hs
@@ -57,7 +57,6 @@ module Data.OldTypeable.Internal {-# DEPRECATED "Use Data.Typeable.Internal inst
 import GHC.Base
 import GHC.Word
 import GHC.Show
-import Data.Maybe
 import Data.List
 import GHC.Num
 import GHC.Real
diff --git a/libraries/base/Data/Typeable/Internal.hs b/libraries/base/Data/Typeable/Internal.hs
index b67f88c446..1a901792c1 100644
--- a/libraries/base/Data/Typeable/Internal.hs
+++ b/libraries/base/Data/Typeable/Internal.hs
@@ -54,7 +54,6 @@ import GHC.Base
 import GHC.Word
 import GHC.Show
 import GHC.Read ( Read )
-import Data.Maybe
 import Data.Proxy
 import GHC.Num
 import GHC.Real
diff --git a/libraries/base/GHC/Base.lhs b/libraries/base/GHC/Base.lhs
index 3267bbfa83..73bfb28d30 100644
--- a/libraries/base/GHC/Base.lhs
+++ b/libraries/base/GHC/Base.lhs
@@ -183,6 +183,29 @@ otherwise = True
 build = error "urk"
 foldr = error "urk"
 -}
+
+\end{code}
+
+%*********************************************************
+%*                                                      *
+\subsection{The Maybe type}
+%*                                                      *
+%*********************************************************
+\begin{code}
+
+-- | The 'Maybe' type encapsulates an optional value.  A value of type
+-- @'Maybe' a@ either contains a value of type @a@ (represented as @'Just' a@),
+-- or it is empty (represented as 'Nothing').  Using 'Maybe' is a good way to
+-- deal with errors or exceptional cases without resorting to drastic
+-- measures such as 'error'.
+--
+-- The 'Maybe' type is also a monad.  It is a simple kind of error
+-- monad, where all errors are represented by 'Nothing'.  A richer
+-- error monad can be built using the 'Data.Either.Either' type.
+--
+data  Maybe a  =  Nothing | Just a
+  deriving (Eq, Ord)
+
 \end{code}
 
 %*********************************************************
@@ -272,6 +295,18 @@ instance Monoid Ordering where
         EQ `mappend` y = y
         GT `mappend` _ = GT
 
+-- | Lift a semigroup into 'Maybe' forming a 'Monoid' according to
+-- <http://en.wikipedia.org/wiki/Monoid>: \"Any semigroup @S@ may be
+-- turned into a monoid simply by adjoining an element @e@ not in @S@
+-- and defining @e*e = e@ and @e*s = s = s*e@ for all @s ∈ S@.\" Since
+-- there is no \"Semigroup\" typeclass providing just 'mappend', we
+-- use 'Monoid' instead.
+instance Monoid a => Monoid (Maybe a) where
+  mempty = Nothing
+  Nothing `mappend` m = m
+  m `mappend` Nothing = m
+  Just m1 `mappend` Just m2 = Just (m1 `mappend` m2)
+
 instance Monoid a => Applicative ((,) a) where
     pure x = (mempty, x)
     (u, f) <*> (v, x) = (u `mappend` v, f x)
@@ -521,6 +556,25 @@ instance Monad ((->) r) where
 instance Functor ((,) a) where
     fmap f (x,y) = (x, f y)
 
+
+instance  Functor Maybe  where
+    fmap _ Nothing       = Nothing
+    fmap f (Just a)      = Just (f a)
+
+instance Applicative Maybe where
+    pure = return
+    (<*>) = ap
+
+instance  Monad Maybe  where
+    (Just x) >>= k      = k x
+    Nothing  >>= _      = Nothing
+
+    (Just _) >>  k      = k
+    Nothing  >>  _      = Nothing
+
+    return              = Just
+    fail _              = Nothing
+
 \end{code}
 
 
diff --git a/libraries/base/GHC/Conc/Signal.hs b/libraries/base/GHC/Conc/Signal.hs
index 2d70419145..3f5eacb572 100644
--- a/libraries/base/GHC/Conc/Signal.hs
+++ b/libraries/base/GHC/Conc/Signal.hs
@@ -10,7 +10,6 @@ module GHC.Conc.Signal
 
 import Control.Concurrent.MVar (MVar, newMVar, withMVar)
 import Data.Dynamic (Dynamic)
-import Data.Maybe (Maybe(..))
 import Foreign.C.Types (CInt)
 import Foreign.ForeignPtr (ForeignPtr)
 import Foreign.StablePtr (castPtrToStablePtr, castStablePtrToPtr,
diff --git a/libraries/base/GHC/Event/EPoll.hsc b/libraries/base/GHC/Event/EPoll.hsc
index 298f450096..f3d635bb5f 100644
--- a/libraries/base/GHC/Event/EPoll.hsc
+++ b/libraries/base/GHC/Event/EPoll.hsc
@@ -40,7 +40,6 @@ available = False
 
 import Control.Monad (when)
 import Data.Bits (Bits, FiniteBits, (.|.), (.&.))
-import Data.Maybe (Maybe(..))
 import Data.Word (Word32)
 import Foreign.C.Error (eNOENT, getErrno, throwErrno,
                         throwErrnoIfMinus1, throwErrnoIfMinus1_)
diff --git a/libraries/base/GHC/Event/Internal.hs b/libraries/base/GHC/Event/Internal.hs
index fcd7886a20..f57cf9b88a 100644
--- a/libraries/base/GHC/Event/Internal.hs
+++ b/libraries/base/GHC/Event/Internal.hs
@@ -24,7 +24,6 @@ module GHC.Event.Internal
 
 import Data.Bits ((.|.), (.&.))
 import Data.List (foldl', intercalate)
-import Data.Maybe (Maybe(..))
 import Foreign.C.Error (eINTR, getErrno, throwErrno)
 import System.Posix.Types (Fd)
 import GHC.Base
diff --git a/libraries/base/GHC/Event/Manager.hs b/libraries/base/GHC/Event/Manager.hs
index f07efba311..9f12ecd9dc 100644
--- a/libraries/base/GHC/Event/Manager.hs
+++ b/libraries/base/GHC/Event/Manager.hs
@@ -56,7 +56,7 @@ import Control.Monad ((=<<), forM_, when, replicateM, void)
 import Data.Bits ((.&.))
 import Data.IORef (IORef, atomicModifyIORef', mkWeakIORef, newIORef, readIORef,
                    writeIORef)
-import Data.Maybe (Maybe(..), maybe)
+import Data.Maybe (maybe)
 import GHC.Arr (Array, (!), listArray)
 import GHC.Base
 import GHC.Conc.Signal (runHandlers)
diff --git a/libraries/base/GHC/Event/PSQ.hs b/libraries/base/GHC/Event/PSQ.hs
index 853958bc29..a623625761 100644
--- a/libraries/base/GHC/Event/PSQ.hs
+++ b/libraries/base/GHC/Event/PSQ.hs
@@ -88,7 +88,6 @@ module GHC.Event.PSQ
     , atMost
     ) where
 
-import Data.Maybe (Maybe(..))
 import GHC.Base
 import GHC.Num (Num(..))
 import GHC.Show (Show(showsPrec))
diff --git a/libraries/base/GHC/Event/Poll.hsc b/libraries/base/GHC/Event/Poll.hsc
index ad2a96f56f..fd05a13799 100644
--- a/libraries/base/GHC/Event/Poll.hsc
+++ b/libraries/base/GHC/Event/Poll.hsc
@@ -28,7 +28,6 @@ available = False
 import Control.Concurrent.MVar (MVar, newMVar, swapMVar)
 import Control.Monad ((=<<), unless)
 import Data.Bits (Bits, FiniteBits, (.|.), (.&.))
-import Data.Maybe (Maybe(..))
 import Data.Word
 import Foreign.C.Types (CInt(..), CShort(..))
 import Foreign.Ptr (Ptr)
diff --git a/libraries/base/GHC/Event/Thread.hs b/libraries/base/GHC/Event/Thread.hs
index 0a82a548da..3d4dc7d405 100644
--- a/libraries/base/GHC/Event/Thread.hs
+++ b/libraries/base/GHC/Event/Thread.hs
@@ -19,7 +19,6 @@ import Control.Exception (finally, SomeException, toException)
 import Control.Monad (forM, forM_, sequence_, zipWithM, when)
 import Data.IORef (IORef, newIORef, readIORef, writeIORef)
 import Data.List (zipWith3)
-import Data.Maybe (Maybe(..))
 import Data.Tuple (snd)
 import Foreign.C.Error (eBADF, errnoToIOError)
 import Foreign.C.Types (CInt(..), CUInt(..))
diff --git a/libraries/base/GHC/Event/TimerManager.hs b/libraries/base/GHC/Event/TimerManager.hs
index cbfce59434..435693a927 100644
--- a/libraries/base/GHC/Event/TimerManager.hs
+++ b/libraries/base/GHC/Event/TimerManager.hs
@@ -42,7 +42,6 @@ import Control.Exception (finally)
 import Control.Monad ((=<<), sequence_, when)
 import Data.IORef (IORef, atomicModifyIORef', mkWeakIORef, newIORef, readIORef,
                    writeIORef)
-import Data.Maybe (Maybe(..))
 import GHC.Base
 import GHC.Conc.Signal (runHandlers)
 import GHC.Num (Num(..))
diff --git a/libraries/base/GHC/IO.hs b/libraries/base/GHC/IO.hs
index 388c81f138..1d86b8d12a 100644
--- a/libraries/base/GHC/IO.hs
+++ b/libraries/base/GHC/IO.hs
@@ -44,7 +44,6 @@ import GHC.Base
 import GHC.ST
 import GHC.Exception
 import GHC.Show
-import Data.Maybe
 
 import {-# SOURCE #-} GHC.IO.Exception ( userError )
 
diff --git a/libraries/base/GHC/IO/BufferedIO.hs b/libraries/base/GHC/IO/BufferedIO.hs
index b715c61380..cc98be76d1 100644
--- a/libraries/base/GHC/IO/BufferedIO.hs
+++ b/libraries/base/GHC/IO/BufferedIO.hs
@@ -25,7 +25,6 @@ import GHC.Base
 import GHC.Ptr
 import Data.Word
 import GHC.Num
-import Data.Maybe
 import GHC.IO.Device as IODevice
 import GHC.IO.Device as RawIO
 import GHC.IO.Buffer
diff --git a/libraries/base/GHC/IO/Device.hs b/libraries/base/GHC/IO/Device.hs
index e20cdf0770..b6c973b7e0 100644
--- a/libraries/base/GHC/IO/Device.hs
+++ b/libraries/base/GHC/IO/Device.hs
@@ -29,7 +29,6 @@ import GHC.Enum
 import GHC.Read
 import GHC.Show
 import GHC.Ptr
-import Data.Maybe
 import GHC.Num
 import GHC.IO
 import {-# SOURCE #-} GHC.IO.Exception ( unsupportedOperation )
diff --git a/libraries/base/GHC/IO/Encoding.hs b/libraries/base/GHC/IO/Encoding.hs
index eb4d74ccfc..9d03276c98 100644
--- a/libraries/base/GHC/IO/Encoding.hs
+++ b/libraries/base/GHC/IO/Encoding.hs
@@ -49,7 +49,6 @@ import GHC.Word
 import Data.IORef
 import Data.Char (toUpper)
 import Data.List
-import Data.Maybe
 import System.IO.Unsafe (unsafePerformIO)
 
 -- -----------------------------------------------------------------------------
diff --git a/libraries/base/GHC/IO/Encoding/Failure.hs b/libraries/base/GHC/IO/Encoding/Failure.hs
index 4b24d06012..6e06213ae2 100644
--- a/libraries/base/GHC/IO/Encoding/Failure.hs
+++ b/libraries/base/GHC/IO/Encoding/Failure.hs
@@ -34,9 +34,6 @@ import GHC.Real ( fromIntegral )
 
 --import System.Posix.Internals
 
-import Data.Maybe
-
-
 -- | The 'CodingFailureMode' is used to construct 'TextEncoding's, and
 -- specifies how they handle illegal sequences.
 data CodingFailureMode
diff --git a/libraries/base/GHC/IO/Encoding/UTF16.hs b/libraries/base/GHC/IO/Encoding/UTF16.hs
index b0ff992a0d..c6dc7c0a76 100644
--- a/libraries/base/GHC/IO/Encoding/UTF16.hs
+++ b/libraries/base/GHC/IO/Encoding/UTF16.hs
@@ -47,7 +47,6 @@ import GHC.IO.Encoding.Failure
 import GHC.IO.Encoding.Types
 import GHC.Word
 import Data.Bits
-import Data.Maybe
 import GHC.IORef
 
 -- -----------------------------------------------------------------------------
diff --git a/libraries/base/GHC/IO/Encoding/UTF32.hs b/libraries/base/GHC/IO/Encoding/UTF32.hs
index eddc4f8693..8d996b14b9 100644
--- a/libraries/base/GHC/IO/Encoding/UTF32.hs
+++ b/libraries/base/GHC/IO/Encoding/UTF32.hs
@@ -47,7 +47,6 @@ import GHC.IO.Encoding.Failure
 import GHC.IO.Encoding.Types
 import GHC.Word
 import Data.Bits
-import Data.Maybe
 import GHC.IORef
 
 -- -----------------------------------------------------------------------------
diff --git a/libraries/base/GHC/IO/Exception.hs b/libraries/base/GHC/IO/Exception.hs
index e7e3316ca9..0f351f0382 100644
--- a/libraries/base/GHC/IO/Exception.hs
+++ b/libraries/base/GHC/IO/Exception.hs
@@ -48,7 +48,6 @@ import GHC.IO
 import GHC.Show
 import GHC.Read
 import GHC.Exception
-import Data.Maybe
 import GHC.IO.Handle.Types
 import Foreign.C.Types
 
diff --git a/libraries/base/GHC/IO/FD.hs b/libraries/base/GHC/IO/FD.hs
index 1134e95f8d..1783125a90 100644
--- a/libraries/base/GHC/IO/FD.hs
+++ b/libraries/base/GHC/IO/FD.hs
@@ -35,7 +35,6 @@ import GHC.Num
 import GHC.Real
 import GHC.Show
 import GHC.Enum
-import Data.Maybe
 import Control.Monad
 import Data.Typeable
 
diff --git a/libraries/base/GHC/IO/Handle/Types.hs b/libraries/base/GHC/IO/Handle/Types.hs
index defa33bbca..fbedeecdbd 100644
--- a/libraries/base/GHC/IO/Handle/Types.hs
+++ b/libraries/base/GHC/IO/Handle/Types.hs
@@ -42,7 +42,6 @@ import GHC.IO.Buffer
 import GHC.IO.BufferedIO
 import GHC.IO.Encoding.Types
 import GHC.IORef
-import Data.Maybe
 import GHC.Show
 import GHC.Read
 import GHC.Word
diff --git a/libraries/base/GHC/MVar.hs b/libraries/base/GHC/MVar.hs
index ff138a5ef2..5bdb6ff82a 100644
--- a/libraries/base/GHC/MVar.hs
+++ b/libraries/base/GHC/MVar.hs
@@ -33,7 +33,6 @@ module GHC.MVar (
     ) where
 
 import GHC.Base
-import Data.Maybe
 import Data.Typeable
 
 data MVar a = MVar (MVar# RealWorld a) deriving( Typeable )
diff --git a/libraries/base/GHC/Show.lhs b/libraries/base/GHC/Show.lhs
index 09c3c56cd9..93320eea1b 100644
--- a/libraries/base/GHC/Show.lhs
+++ b/libraries/base/GHC/Show.lhs
@@ -52,7 +52,6 @@ module GHC.Show
 
 import GHC.Base
 import GHC.Num
-import Data.Maybe
 import GHC.List ((!!), foldr1, break)
 \end{code}
 
diff --git a/libraries/base/GHC/Weak.lhs b/libraries/base/GHC/Weak.lhs
index bffd9f8236..5405a302ed 100644
--- a/libraries/base/GHC/Weak.lhs
+++ b/libraries/base/GHC/Weak.lhs
@@ -32,7 +32,6 @@ module GHC.Weak (
     ) where
 
 import GHC.Base
-import Data.Maybe
 import Data.Typeable
 
 {-|
diff --git a/libraries/base/Numeric.hs b/libraries/base/Numeric.hs
index 4a1a5b121a..7cba671309 100644
--- a/libraries/base/Numeric.hs
+++ b/libraries/base/Numeric.hs
@@ -65,7 +65,6 @@ import GHC.Real
 import GHC.Float
 import GHC.Num
 import GHC.Show
-import Data.Maybe
 import Text.ParserCombinators.ReadP( ReadP, readP_to_S, pfail )
 import qualified Text.Read.Lex as L
 
diff --git a/libraries/base/Text/Read.hs b/libraries/base/Text/Read.hs
index 6c9d89db76..18c485fea1 100644
--- a/libraries/base/Text/Read.hs
+++ b/libraries/base/Text/Read.hs
@@ -47,7 +47,6 @@ module Text.Read (
 import GHC.Base
 import GHC.Read
 import Data.Either
-import Data.Maybe
 import Text.ParserCombinators.ReadP as P
 import Text.ParserCombinators.ReadPrec
 import qualified Text.Read.Lex as L
diff --git a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
index 650410841e..268838e195 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
@@ -512,8 +512,8 @@ trueName  = mkNameG DataName "ghc-prim" "GHC.Types" "True"
 falseName = mkNameG DataName "ghc-prim" "GHC.Types" "False"
 
 nothingName, justName :: Name
-nothingName = mkNameG DataName "base" "Data.Maybe" "Nothing"
-justName    = mkNameG DataName "base" "Data.Maybe" "Just"
+nothingName = mkNameG DataName "base" "GHC.Base" "Nothing"
+justName    = mkNameG DataName "base" "GHC.Base" "Just"
 
 leftName, rightName :: Name
 leftName  = mkNameG DataName "base" "Data.Either" "Left"