{-# LANGUAGE DataKinds    #-}
{-# LANGUAGE TypeFamilies #-}

import Data.Kind (Type)

main :: IO ()
main = pure ()

-- Some type classes
class Kinded x where
  type Kind x :: Type

class Kinded x => Singlify x where
  data Singleton x :: Kind x -> Type -> Type -- CHANGE: added one Type here

-- Now some instances for above
data X
data MyKind = A
data Bla -- CHANGE: defined this here

instance Kinded X where
  type Kind X = MyKind

instance Singlify X where
  data Singleton X s t where    -- CHANGE: added t
    SingA :: Singleton X 'A Bla -- CHANGE: added Bla
    
    {- note that the following alternatives do NOT work, the last one is interesting:
    
    SingA :: Singleton X 'A Int
    SingA :: Singleton X 'A String
    SingA :: Singleton X 'A Bool
    SingA :: Singleton X 'A X
    ...
    -}