[Haskell] Forcing Type Class Equality

[john lask]

NB

the essence what I am trying to do is to define a proxy class Foo for class 
Ba1 I would have thought that something as simple as the following would 
have worked ??

class Ba1 a where
   dosomething :: a -> IO ()

ba1 :: Ba1 a => a -> IO ()
ba1 x = dosomething x

instance Ba1 Int where
   dosomething x = print x

instance Ba1 Char where
   dosomething x = print x

what I wish to do is declare another function

class Foo a
instance Foo a => Ba1 a

proxy :: Foo a => a -> IO ()
proxy x = ba1 x

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