gistfile1.txt

{-# LANGUAGE AllowAmbiguousTypes, FlexibleInstances, MultiParamTypeClasses, ScopedTypeVariables, TypeApplications, UndecidableInstances #-}

class Lift' m a b where
  lift' :: m a -> b

instance (Applicative m) => Lift' m a (m a) where
  lift' = id

instance (Applicative m, Lift' m a b) => Lift' m (x -> a) (m x -> b) where
  lift' f = lift' . ((<*>) f)

lift :: forall m a b. (Applicative m, Lift' m a b) => a -> b
lift = lift' . pure @m


main = do
  a <- ((lift @IO :: (String -> String -> String) -> (IO String -> IO String -> IO String)) (++)) (pure "Hello, ") (pure "world")
  putStrLn a