Hi all,

I'm surprised this doesn't work:

data SomeData = forall e. (Typeable e, Eq e) => SomeData e

(===) :: (Typeable a, Typeable b, Eq a, Eq b) => a -> b -> Bool
(===) x y = cast x == Just y

test :: SomeData' -> Bool
test (SomeData' e) | e === Nothing = True
test _ = False

It says
Could not deduce (Eq a1) arising from a use of ‘===’

How can I achieve something of the same effect?

Thanks

Corentin