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{-# LANGUAGE TypeFamilies, Rank2Types #-}
-- This test made the type checker produce an
-- ill-kinded coercion term.
module Roman where
import Control.Monad.ST
type family Mut (v :: * -> *) :: * -> * -> *
type family State (m :: * -> *)
type instance State (ST s) = s
unsafeFreeze :: Mut v (State (ST s)) a -> ST s (v a)
unsafeFreeze = undefined
new :: (forall v s. ST s (v s a)) -> v a
new p = runST (do
mv <- p
unsafeFreeze mv)
---------------------------------------------
-- Here's a simpler version that also failed
type family FMut :: * -> * -- No args
-- Same thing happens with one arg
type family FState (m :: *)
type instance FState Char = Int
funsafeFreeze :: FMut (FState Char) -> ()
funsafeFreeze = undefined
flop :: forall mv. mv Int
flop = undefined
noo = flop `rapp` funsafeFreeze
rapp :: a -> (a->()) -> ()
rapp arg fun = fun arg
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