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Created September 5, 2021 14:16
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applicative bug
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bug.hs
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ApplicativeDo #-}
module ApplicativeDont (foo) where
data M a
data N a
instance Functor M
instance Applicative M
instance Functor N
instance Applicative N
instance Monad N
newtype Alias = Alias (forall a. a -> M a)
foo :: N (M ())
foo = do
pure ()
Alias mt <- undefined
pure ()
pure $ (\c b -> ()) <$> mt 'a' <*> mt False
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