[commit: packages/haskeline] master: Generalise constraints for InputT instances (7289f1f)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/haskeline

On branch  : master
Link       : http://git.haskell.org/packages/haskeline.git/commitdiff/7289f1f65311f6072e7cb4321cf01e0fa81d3dae

>---------------------------------------------------------------

commit 7289f1f65311f6072e7cb4321cf01e0fa81d3dae
Author: Herbert Valerio Riedel <hvr at gnu.org>
Date:   Mon Nov 23 08:55:21 2015 +0100

    Generalise constraints for InputT instances
    
    I'm not sure why the code was written the way it was, but it seems we
    can do better by letting GHC directly reuse `ReaderT`'s instances as
    well as relaxing the constraints from
    
        instance Monad m       => Functor     (InputT m)
        instance Monad m       => Applicative (InputT m)
        instance Monad m       => Monad       (InputT m)
    
    to
    
        instance Functor     m => Functor     (InputT m)
        instance Applicative m => Applicative (InputT m)
        instance Monad       m => Monad       (InputT m)
    
    This looks the same on GHC 7.8 (pre-AMP) as well as GHC 7.10 (post-AMP)


>---------------------------------------------------------------

7289f1f65311f6072e7cb4321cf01e0fa81d3dae
 System/Console/Haskeline/InputT.hs | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/System/Console/Haskeline/InputT.hs b/System/Console/Haskeline/InputT.hs
index 383cf5f..c1ee55e 100644
--- a/System/Console/Haskeline/InputT.hs
+++ b/System/Console/Haskeline/InputT.hs
@@ -47,19 +47,12 @@ newtype InputT m a = InputT {unInputT ::
                                 (ReaderT (IORef KillRing)
                                 (ReaderT Prefs
                                 (ReaderT (Settings m) m)))) a}
-                            deriving (Monad, MonadIO, MonadException)
+                            deriving (Functor, Applicative, Monad, MonadIO, MonadException)
                 -- NOTE: we're explicitly *not* making InputT an instance of our
                 -- internal MonadState/MonadReader classes.  Otherwise haddock
                 -- displays those instances to the user, and it makes it seem like
                 -- we implement the mtl versions of those classes.
 
-instance Monad m => Functor (InputT m) where
-    fmap = liftM
-
-instance Monad m => Applicative (InputT m) where
-    pure = return
-    (<*>) = ap
-
 instance MonadTrans InputT where
     lift = InputT . lift . lift . lift . lift . lift