Move withRunInIO into typeclass #13

fpco · Jan 2, 2018 · a99e302 · a99e302
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diff --git a/unliftio-core/ChangeLog.md b/unliftio-core/ChangeLog.md
@@ -3,6 +3,7 @@
 * Doc improvements.
 * Inline functions in `Control.Monad.IO.Unlift` module [#4](https://github.com/fpco/unliftio/pull/4).
 * Fully polymorphic `withRunInIO` [#12](https://github.com/fpco/unliftio/pull/12).
+* Move `withRunInIO` into the `MonadUnliftIO` typeclass itself[#13](https://github.com/fpco/unliftio/issues/13)
 
 ## 0.1.0.0
 

diff --git a/unliftio-core/src/Control/Monad/IO/Unlift.hs b/unliftio-core/src/Control/Monad/IO/Unlift.hs
@@ -6,7 +6,6 @@ module Control.Monad.IO.Unlift
   , UnliftIO (..)
   , askRunInIO
   , withUnliftIO
-  , withRunInIO
   , toIO
   , MonadIO (..)
   ) where
@@ -52,15 +51,26 @@ newtype UnliftIO m = UnliftIO { unliftIO :: forall a. m a -> IO a }
 --
 -- @since 0.1.0.0
 class MonadIO m => MonadUnliftIO m where
+  {-# MINIMAL askUnliftIO | withRunInIO #-}
   -- | Capture the current monadic context, providing the ability to
   -- run monadic actions in 'IO'.
   --
   -- See 'UnliftIO' for an explanation of why we need a helper
   -- datatype here.
   -- @since 0.1.0.0
   askUnliftIO :: m (UnliftIO m)
+  askUnliftIO = withRunInIO (\run -> return (UnliftIO run))
   -- Would be better, but GHC hates us
   -- askUnliftIO :: m (forall a. m a -> IO a)
+
+  -- | Convenience function for capturing the monadic context and running an 'IO'
+  -- action with a runner function. The runner function is used to run a monadic
+  -- action @m@ in @IO@.
+  --
+  -- @since 0.1.0.0
+  {-# INLINE withRunInIO #-}
+  withRunInIO :: ((forall a. m a -> IO a) -> IO b) -> m b
+  withRunInIO inner = withUnliftIO $ \u -> inner (unliftIO u)
 instance MonadUnliftIO IO where
   {-# INLINE askUnliftIO #-}
   askUnliftIO = return (UnliftIO id)
@@ -94,15 +104,6 @@ askRunInIO = liftM unliftIO askUnliftIO
 withUnliftIO :: MonadUnliftIO m => (UnliftIO m -> IO a) -> m a
 withUnliftIO inner = askUnliftIO >>= liftIO . inner
 
--- | Convenience function for capturing the monadic context and running an 'IO'
--- action with a runner function. The runner function is used to run a monadic
--- action @m@ in @IO@.
---
--- @since 0.1.0.0
-{-# INLINE withRunInIO #-}
-withRunInIO :: MonadUnliftIO m => ((forall a. m a -> IO a) -> IO b) -> m b
-withRunInIO inner = withUnliftIO $ \u -> inner (unliftIO u)
-
 -- | Convert an action in @m@ to an action in @IO@.
 --
 -- @since 0.1.0.0