Provide default MonadIO instance for IO.

diff --git a/compiler/utils/MonadUtils.hs b/compiler/utils/MonadUtils.hs
index 59bf509..85d8642 100644 (file)
--- a/compiler/utils/MonadUtils.hs
+++ b/compiler/utils/MonadUtils.hs
@@ -73,6 +73,7 @@ instance Applicative IO where
 class Monad m => MonadIO m where
     liftIO :: IO a -> m a
 
+instance MonadIO IO where liftIO = id
 #endif
 
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