Why not use rank 2 polymorphism for callCC

[SmartHypercube]

I think rank 2 polymorphism is a must-have for callCC, or this code will not compile:

f :: Int -> String
f x = (`runCont` id) $ callCC $ \exit -> do
    y <- case x of
        0 -> exit "error: x == 0"
        _ -> pure x
    yString <- case y of
        1 -> exit "error: y == 1"
        _ -> pure $ show y
    pure yString

When calling functions like error, throwIO, or exit, which will never produce "normal" outputs, I generally expect the return type to be forall a. a in order to fit in any hole. But the exit produced by callCC does not work as expected. I wonder is there any specific reason?

I tried searching for related discussions, but all I could find is this article. It seems nobody is bothered by this? I have to use absurd to make it work in my code (absurd <$> exit "error: x == 0"). I'm curious about how others deal with this lack of polymorphism.

[kozross]

I'm definitely keen on making this happen, but this requires a major version bump. Once we land 2.3.1, I'm sure @emilypi wouldn't object to this change.

[emilypi]

No objections here.