Haskell's missing mutable reference type

danidiaz:

In my personal projects, I prefer to work with bare IO instead of usign an app-wide ReaderT

You could still do that! It’s only that when using libFun, you would locally instantiate that m with ReaderT Logger IO, which (modulo newtypes) would give you

libFun ::
  (String -> Logger -> IO ()) ->
  (forall r. Int -> (Logger -> IO ()) -> Logger -> IO ()) ->
  Logger -> IO ()

which is exactly the type you would want for the non-IOScopedRef API

danidiaz:

it’s convenient as an alternative to ReaderT

The problem is that it’s not an alternative because you still need to pass the IOScopedRef into whatever wants to access it