Change type of launchAff to avoid duplicate label errors

[no-longer-on-githu-b]

The current type is:

launchAff :: forall e a. Aff e a -> Eff (err :: EXCEPTION | e) (Canceler e)

This causes duplicate label issues when the Aff action already has the err :: EXCEPTION effect in its type.

This problem should be solved by using the following type:

launchAff :: forall e a. Aff (err :: EXCEPTION | e) a -> Eff (err :: EXCEPTION | e) (Canceler e)

Most old code should keep working because adding an effect to an action type isn't a problem.

[garyb]

The reason this was changed in the first place is that it makes the type lie. Launching an aff will never raise an exception.

[natefaubion]

It's not a lie, launchAff always has the potential to raise an exception, but it might not necessarily raise an exception you can catch.

[garyb]

(See #32 / #33).

On the other hand, it is a pain to work with as long as duplicate rows are disallowed, so I don't like either option particularly right now.

[garyb]

Ah actually, this is a little different than the linked discussion, and I even suggested the above. In that case, 👍.

[natefaubion]

This is irrelevant now the row restriction has been lifted.