Move Control.Monad.void into Data.Functor

Both modules still export `void`, but `void`'s implementation now lives in
Data.Functor where it actually belongs in (as it doesn't need a Monad context)

The desired side-effect of this is to invert the import-dep
between Control.Monad and Data.Functor.

Reviewed By: ekmett, austin

Differential Revision: https://phabricator.haskell.org/D224

2 files changed, 6 insertions, 6 deletions

diff --git a/libraries/base/Control/Monad.hs b/libraries/base/Control/Monad.hs
index 534e6527d0..0597055da9 100644
--- a/libraries/base/Control/Monad.hs
+++ b/libraries/base/Control/Monad.hs
@@ -76,6 +76,7 @@ module Control.Monad
     , (<$!>)
     ) where
 
+import Data.Functor ( void )
 import Data.Maybe
 
 import GHC.List
@@ -159,10 +160,6 @@ forever a   = let a' = a >> a' in a'
 -- Use explicit sharing here, as it is prevents a space leak regardless of
 -- optimizations.
 
--- | @'void' value@ discards or ignores the result of evaluation, such as the return value of an 'IO' action.
-void :: Functor f => f a -> f ()
-void = fmap (const ())
-
 -- -----------------------------------------------------------------------------
 -- Other monad functions
 
diff --git a/libraries/base/Data/Functor.hs b/libraries/base/Data/Functor.hs
index 00cc254a8b..43ca8218f4 100644
--- a/libraries/base/Data/Functor.hs
+++ b/libraries/base/Data/Functor.hs
@@ -23,8 +23,7 @@ module Data.Functor
       void,
     ) where
 
-import Control.Monad ( void )
-import GHC.Base ( Functor(..), flip )
+import GHC.Base ( Functor(..), const, flip )
 
 infixl 4 <$>
 
@@ -40,3 +39,7 @@ infixl 4 $>
 ($>) :: Functor f => f a -> b -> f b
 ($>) = flip (<$)
 
+-- | @'void' value@ discards or ignores the result of evaluation, such as the
+-- return value of an 'IO' action.
+void :: Functor f => f a -> f ()
+void = fmap (const ())