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{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeFamilies #-}
-- A very bogus program (multiple errors) but
-- sent GHC 6.12 into a loop
module T3330a where
newtype Writer w a = Writer { runWriter :: (a, w) }
execWriter :: Writer w a -> w
execWriter m = snd (runWriter m)
data AnyF (s :: * -> *) = AnyF
class HFunctor (f :: (* -> *) -> * -> *)
type family PF (phi :: * -> *) :: (* -> *) -> * -> *
children :: s ix -> (PF s) r ix -> [AnyF s]
children p x = execWriter (hmapM p collect x)
collect :: HFunctor (PF s) => s ix -> r ix -> Writer [AnyF s] (r ix)
collect = undefined
hmapM :: (forall ix. phi ix -> r ix -> m (r' ix))
-> phi ix -> f r ix -> m (f r' ix)
hmapM = undefined
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