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{-# LANGUAGE DataKinds, UndecidableInstances #-}
{-# LANGUAGE TypeFamilies, TypeOperators, FlexibleContexts #-}
module T2 where
import GHC.TypeLits
type family IntRep a where
IntRep Int = Integer
IntRep Integer = Integer
IntRep Bool = Integer
IntRep a = TypeError (Text "The type '" :<>: ShowType a :<>:
Text "' cannot be represented as an integer.")
convert :: Num (IntRep a) => a -> IntRep a
convert _ = 5
err = convert id
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