Allow specifying a more concrete Throwable type for retrying, alternative

[serras]

This is an alternative approach to #3414, which I think gives us better ergonomics

The main changes are:

• The retryOrElseEither function gets a new overload with a KClass<E> parameter, which is used to make the instance checks. The reified versions call those with E::class.
• The approach in #3414 was limited to the case in which you had Schedule<E, A> and also a KClass<E>. However, this shouldn't be the case, as the check for E is actually used to filter out the desired cases.
  • So now the functions are more polymorphic, to <E: Throw, Throw: Throwable> Schedule<Throw, A>.retry(KClass)`
  • The overload resolution still works, I had to make no changed in the test files.

[github-actions[bot]]

Kover Report

File	Coverage [68.21%]
arrow-libs/resilience/arrow-resilience/src/commonMain/kotlin/arrow/resilience/Schedule.kt	68.21%

Total Project Coverage	61.06%

[serras]

I think I got it!! Actually variants using E everywhere is all we need!

fun <E: Throwable, A> Schedule<E, *>.retry(...)

This works without the intermediate E: Throw: Throwable because of the contravariance of Schedule. That is, since E: Throwable, then Schedule<Throwable, ...>: Schedule<E, ...>, as needed for the function to apply. I think this gives great ergonomics, as shown by the tests:

• If you use s.retry { ... }, the type E is taken from the type of s. So the behavior is that all the exceptions are retried.
• But you can also use s.retry<IllegalStateException, _> { ... } if you want a more concrete type to be filtered than the one coming from s. Furthermore, we ensure that IllegalStateException is indeed a subtype of the input to s, as required.

[nomisRev]

But you can also use s.retry<IllegalStateException, _> { ... } if you want a more concrete type to be filtered than the one coming from s. Furthermore, we ensure that IllegalStateException is indeed a subtype of the input to s, as required.

That's really nice ergonomics, also I have really underused _. I need to used it more, would also be good to use _ more in the Arrow docs IMHO. It looks so much better.