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{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeInType #-}
module T15122 where
import Data.Kind
import Data.Proxy
data IsStar (a :: k) where
IsStar :: IsStar (a :: Type)
type family F (a :: k) :: k
foo :: (F a ~ F b) => IsStar a -> Proxy b
-> Proxy (F a) -> Proxy (F b)
foo IsStar _ p = p
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