AsyncLaws.thrownInRegisterIsRaiseError cannot be upheld about cats-effect HOT 3 CLOSED

So, there is an idempotency check (specifically applied here). From a performance standpoint, I'm pretty sure AtomicBoolean is an order of magnitude faster than raw synchronization (especially when uncontested), but even beyond that, we could do even better with a method handle and a switch point if we really wanted to make it that fast.

The problem is that if IO doesn't do this, it either has to capture an ExecutionContext (in order to use reportFailure) or just swallow the error altogether, neither of which seem like particularly good solutions relative to the rest of the design.

But all that aside… I tend to agree that the law is too restrictive. It basically means that implementors can only implement their types in this way, and I don't think that's what we want to say. So I think you're right that we should remove the law and add it as a test specifically for IO.

from cats-effect.

Well, yeah, on top of Java 8 that getAndSet operation is pretty fast, using platform intrinsics and if you do it once "per program" it's not a problem. Also when dealing with say a Scala Promise, it has trySuccess baked in.

So yes, it's not IO's implementation I'm complaining about, but this law :-)

It would have been helpful to specify an Either in that law ... such that we could specify equivalence with raiseError(ex) or never. Such a law would still disallow blowing the current call-stack for example.

from cats-effect.

It would have been helpful to specify an Either in that law ... such that we could specify equivalence with raiseError(ex) or never. Such a law would still disallow blowing the current call-stack for example.

Hmm, that's an interesting idea, though I'm not sure how many implementation flaws that would actually catch. A bigger problem though is that the current Eq[IO[A]] implementation I'm using in the laws is unable to check equivalence with never. I haven't actually looked at how Monix's tests do that…

from cats-effect.