monad-control type inferencence

Main.hs

{-# LANGUAGE ScopedTypeVariables, FlexibleContexts #-}

module Main where

import Control.Monad.Trans.Control
import Control.Exception
import Control.Monad.Trans.State
import Control.Monad.IO.Class

withSomething :: forall a m. (MonadBaseControl IO m) => (Int -> m a) -> m (Maybe a)
withSomething f =
    control $ \run -> liftIO $ catch
            (run $ Just <$> f 10)
            (\(_ :: SomeException) -> run $ return (Nothing :: Maybe a))

main :: IO ()
main = do
    _ <- flip runStateT (0 :: Int) $ do
        withSomething (\_ -> modify' (+ 10))
    return ()

{-
main :: IO ()
main = do
    _ <- flip runStateT (0 :: Int) $ do
        control $ \run -> liftIO $
            catch
                (putStrLn "Hello World" >> run (modify' (+ 10) >> return (Just (10 :: Int))))
                (\(_ :: SomeException) ->  run (modify' (+ 10) >> return Nothing))
    return ()
-}

mc-test.cabal

name:                mc-test
version:             0.1.0.0
synopsis:            Simple project template from stack
cabal-version:       >=1.10

executable mc-test
  hs-source-dirs:      src
  main-is:             Main.hs
  default-language:    Haskell2010
  ghc-options:         -Wall
  build-depends:       base >= 4.7 && < 5
                     , monad-control
                     , mtl
                     , transformers