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llelf/gadt-coerce-bug.lhs

Last active August 29, 2015 14:04
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gadt-coerce-bug.lhs
> {-# LANGUAGE RankNTypes, DataKinds, KindSignatures, GADTs #-}
> import Unsafe.Coerce
> data M = A | B deriving (Show, Eq)
> data V1 :: M -> * where
> V1A :: Int -> V1 A
> V1B :: Double -> V1 B
> V1a :: () -> V1 a
> zu :: V1 a
> zu = unsafeCoerce (V1A 2)
> main = putStrLn $ case zu of
> V1A{} -> "A"
> V1B{} -> "B"
> V1a{} -> "O_o"
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