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{-# LANGUAGE PolyKinds, DataKinds, KindSignatures, RankNTypes,
TypeFamilies, FlexibleInstances, UndecidableInstances #-}
module T6118 where
import GHC.Exts (Any)
import Data.Kind (Type)
data Nat = Zero | Succ Nat
data List a = Nil | Cons a (List a)
class SingE (a :: k) where
type Demote a :: Type
instance SingE (a :: Bool) where
type Demote a = Bool
instance SingE (a :: Nat) where
type Demote a = Nat
instance SingE (a :: Maybe k) where
type Demote (a :: Maybe k) = Maybe (Demote (Any :: k))
instance SingE (a :: List k) where
type Demote (a :: List k) = List (Demote (Any :: k))
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