Do we need `ErrorT` now we have `Except`?

[garyb]

Do we need `ErrorT` now we have `Except`?

[hdgarrood]

The only reason we might need it, as far as I can tell, is if existing code relied on it. Perhaps we can deprecate it and remove it in the next release?

[garyb]

Sounds good to me. @paf31?

[paf31]

Well, the only thing that differs, as I understand it, is the MonadPlus instance. Instead of an Error constraint (which gives an error for mempty), we use a Monoid constraint, which gives an empty error and a way of combining parallel errors. I can't think of a case where you wouldn't be able to use ExceptT, and using the First monoid gives a smooth transition I think. So I say 👍

[hdgarrood]

I think this can be closed now?

[garyb]

Yep!