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{-# LANGUAGE ExplicitForAll #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeApplications #-}
module T2600 where
-- ** See trac #10595 for why we're okay with this generating warnings! **
class T t where
to :: [a] -> t a
from :: t a -> [a]
tmap :: (a -> a) -> t a -> t a
{-# RULES
"myrule" forall t a. forall f x.
from (tmap f (to x :: t a)) = map f (from (to x :: t a))
#-}
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