-- Test restricted functionality: Data.Typeable
:unset +s
:set -XSafe
:set -XDeriveDataTypeable
:set -XStandaloneDeriving

:m + Data.OldTypeable

data H = H {h :: String} deriving (Typeable, Show)

data G = G [Int] deriving (Show)

instance Typeable G where { typeOf _ = typeOf (undefined :: H) }

let x = H "Hello"
let y = G [0]

x
y

let (Just y_as_H) = (cast y) :: Maybe H
y_as_H