Why not use rank 2 polymorphism for `callCC`

I think rank 2 polymorphism is a must-have for `callCC`, or this code will not compile:
```haskell
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](https://wiki.haskell.org/MonadCont_done_right). 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.

Start by inspecting the mtl callCC definition and its type signature, then reproduce the supplied f example and compare it with the MonadCont_done_right article. Done should be a maintainer-backed explanation or a clearly scoped decision about whether rank-2 polymorphism is required.

Written by the indexing model from the issue text.