MonadIO considered harmful

[Josh Miller]

Decoder provides a MonadIO instance, which means a decoder can launch nukes. decodeEither centralizes the unsafePerformIO because it is convenient to use IO internally for exceptions and the unliftio machinery.

So if we lose MonadIO then we lose MonadUnliftIO, and we'll have to refactor how we handle error reporting. I think using a continuation-style like how attoparsec does it could be the better approach. All FFI operations will then need to use unsafePerformIO.

Alternatively, we can maybe get away with defining our own versions of lifting/unlifting IO and never export them.