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konn/Explosion.hs

Created October 1, 2019 10:40
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Explosion.hs
{-# LANGUAGE PolyKinds, DataKinds, TypeFamilies, GADTs, DeriveDataTypeable, TypeApplications #-}
data Foo (a :: Maybe b) where { Any :: Foo a; Bang :: Foo (Just t) }
newtype F a (t :: Maybe s) (u :: Foo t)
= F { runF :: a} deriving (Show, Eq, Ord, Typeable)
main :: IO ()
main = print $ typeRep $ Proxy @(F Int ('Just ()) Any)
-- ~> No instance for (Typeable (F2 Int ('Just ())))
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