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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE EmptyCase #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StandaloneKindSignatures #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
module RepPolyCase2 where
import Data.Kind
import GHC.Exts
type Rep :: Type -> RuntimeRep
type family Rep a
class Unboxable a where
type Unbox a :: TYPE (Rep a)
unbox :: a -> Unbox a
type instance Rep Int = IntRep
instance Unboxable Int where
type Unbox Int = Int#
unbox (I# i#) = i#
type instance Rep Double = DoubleRep
instance Unboxable Double where
type Unbox Double = Double#
unbox (D# d#) = d#
x :: () -> ()
x _ = case unbox (3 :: Int) of { _ -> () }
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