Fix memory leak

[ppressives]

After upgrading Monix to the latest version I found a memory leak related to the new bracket implementation.

Git bisect shows the culprit commit:
#1120

Below is a simple piece of code that reproduces the issue:
F.guarantee(F.unit)(F.unit).foreverM - it fails with OutOfMemoryError on monix.eval.Task, but works fine with cats.effect.IO

I'm not sure if this is a correct fix of the issue and I need help to write a test on this case

[Avasil]

I feel like we could call ctx.connection.pop() in unsafeRecover and unsafeApply which I removed by mistake in the PR you mentioned

[ppressives]

If I put this call there, tests fail. I think it breaks the feature you did in that PR.

[Avasil]

Ah, I see.

I think we could do it in a similar way to Cats IO: https://github.com/typelevel/cats-effect/blob/master/core/shared/src/main/scala/cats/effect/internals/IOBracket.scala#L189

so

  private[this] val disableUncancelableAndPop: (Any, Throwable, Context, Context) => Context =
    (_, _, old, _) => {
      old.connection.pop()
      old
    }

instead of a null in ContextSwitch.

I'm not able to check right now but the testa should pass since they are passing for Cats IO and hopefully the memory leak will go away :)

[ppressives]

Sure, it works fine. Thank you!

[Avasil]

Big thank you!

I'm not sure if this is a correct fix of the issue and I need help to write a test on this case

I think we're fine skipping the test if it takes a long time to go out of memory

[Avasil]

Thank you!

Do you need a snapshot version release / official release right now?
I'm hoping to finish everything for 3.2.2 release within 1-2 weeks but I am considering to pull the trigger earlier considering the severity of the issue

[ppressives]

I rolled back Monix to 3.1.0 in my project, so it can wait for some time.