bracketReleaseIsCalledOnCompletedError assumes generators never fail

[johnynek]

see:

cats-effect/laws/shared/src/main/scala/cats/effect/laws/AsyncLaws.scala

Line 74 in 504c437

def bracketReleaseIsCalledOnCompletedOrError[A, B](fa: F[A], b: B) = {

since bracketCase must return an F[B], if the A => F[B] returns a failed F[B] the result must be a failure. However, this law is requiring it be equivalent to a pure which we can't guarantee in general.

I had to weaken an effect test in order to get this law (and only this law) to pass.

[johnynek]

@alexandru do you know why we shouldn't change it from br.as(()) to br.attempt *> promise.get? that seems like the semantics we want actually.