Make Applicative a superclass of Monad

Summary:
This includes pretty much all the changes needed to make `Applicative`
a superclass of `Monad` finally. There's mostly reshuffling in the
interests of avoid orphans and boot files, but luckily we can resolve
all of them, pretty much. The only catch was that
Alternative/MonadPlus also had to go into Prelude to avoid this.

As a result, we must update the hsc2hs and haddock submodules.

Signed-off-by: Austin Seipp <austin@well-typed.com>

Test Plan: Build things, they might not explode horribly.

Reviewers: hvr, simonmar

Subscribers: simonmar

Differential Revision: https://phabricator.haskell.org/D13

1 files changed, 12 insertions, 5 deletions

diff --git a/libraries/base/Text/ParserCombinators/ReadPrec.hs b/libraries/base/Text/ParserCombinators/ReadPrec.hs
index 235436c4d6..7098b50531 100644
--- a/libraries/base/Text/ParserCombinators/ReadPrec.hs
+++ b/libraries/base/Text/ParserCombinators/ReadPrec.hs
@@ -16,9 +16,9 @@
 -----------------------------------------------------------------------------
 
 module Text.ParserCombinators.ReadPrec
-  ( 
+  (
   ReadPrec,
-  
+
   -- * Precedences
   Prec,
   minPrec,
@@ -61,7 +61,7 @@ import qualified Text.ParserCombinators.ReadP as ReadP
   , pfail
   )
 
-import Control.Monad( MonadPlus(..) )
+import Control.Monad( MonadPlus(..), Alternative(..) )
 import GHC.Num( Num(..) )
 import GHC.Base
 
@@ -75,17 +75,24 @@ newtype ReadPrec a = P (Prec -> ReadP a)
 instance Functor ReadPrec where
   fmap h (P f) = P (\n -> fmap h (f n))
 
+instance Applicative ReadPrec where
+    pure = return
+    (<*>) = ap
+
 instance Monad ReadPrec where
   return x  = P (\_ -> return x)
   fail s    = P (\_ -> fail s)
   P f >>= k = P (\n -> do a <- f n; let P f' = k a in f' n)
-  
+
 instance MonadPlus ReadPrec where
   mzero = pfail
   mplus = (+++)
 
+instance Alternative ReadPrec where
+    empty = mzero
+    (<|>) = mplus
+
 -- precedences
-  
 type Prec = Int
 
 minPrec :: Prec