data Bad : Type where
     MkBad : (Bad -> Int) -> Int -> Bad
     MkBad' : Int -> Bad

foo : Bad -> Int
foo (MkBad f i) = f (MkBad' i)
foo (MkBad' x) = x

foo2 : Bad -> Int
foo2 b = case b of
              MkBad f i => f (MkBad' i)
              MkBad' x => x

data T : Type -> Type where
     MkT : T (T a) -> T a