ref: bdd38072a2fa4108fff41da806309074e79ce6de
dir: /tests/PolyKind.hs/
module PolyKind(main) where
import Prelude
type XProxy :: forall (k::Kind) . k -> Type
data XProxy a = XProxy
data TypeRep = TypeRep String [TypeRep]
mkAppTy :: TypeRep -> TypeRep -> TypeRep
mkAppTy (TypeRep tc trs) tr = TypeRep tc (trs ++ [tr])
instance Show TypeRep where
show (TypeRep s []) = s
show (TypeRep s ts) = "(" ++ unwords (s : map show ts) ++ ")"
type Typeable :: forall (k::Kind) . k -> Constraint
class Typeable a where
typeRep :: forall proxy . proxy a -> TypeRep
typeOf :: forall a . Typeable a => a -> TypeRep
typeOf _ = typeRep (XProxy :: XProxy a)
instance Typeable Int where
typeRep _ = TypeRep "Int" []
instance Typeable IO where
typeRep _ = TypeRep "IO" []
instance forall f a . (Typeable f, Typeable a) => Typeable (f a) where
typeRep _ = mkAppTy (typeRep (XProxy :: XProxy f)) (typeRep (XProxy :: XProxy a))
main :: IO ()
main = do
print $ typeRep (XProxy :: XProxy Int)
print $ typeRep (XProxy :: XProxy IO)
print $ typeRep (XProxy :: XProxy (IO Int))