Make Compiler.Target extend MonadCancelThrow

[bplommer]

This is intended to facilitate using Target as a context bound when you need MonadCancelThrow but don't specifically need either Sync or Concurrent.

[kubukoz]

Personal take, I wish Target didn't extend either of these traits at all... but I guess this avoids the conflict since you can no longer require Target and a typeclass with only partial overlap?

[bplommer]

Personal take, I wish Target didn't extend either of these traits at all...

Why's that?

but I guess this avoids the conflict since you can no longer require Target and a typeclass with only partial overlap?

Yeah - as things stand, if you need both Target and MonadCancelThrow you either have ambiguous instances of MonadThrow or you pick one of Sync or Concurrent - then if you have dependencies that made both choices you end up using Async to satisfy both, when one or the other should have sufficed. (That's currently the situation with http4s, for example, where Target is derived in some cases via Sync and in others via Concurrent.)

[kubukoz]

Why's that?

Conflicts with other context bounds when you want to use extension methods for a common subset (e.g. .map), thus requiring PRs like this one :D

I guess there's a reason why I use Compiler[F, F] instead

[bplommer]

Linking this http4s PR to use Target as a context bound in case anyone wants to weigh in on why the whole thing is a bad idea.

[mpilquist]

I pushed an additional commit to remove some of the intermediate classes.