defer blocks discarding unit effects

[johnhungerford]

Minimized example

import kyo.*

def runInner: Unit < Async = defer:
  await(Console.println("test"))

@main def main(): Unit =
  import AllowUnsafe.embrace.danger
  val _ =  KyoApp.Unsafe.runAndBlock(Duration.Infinity)(runInner)

scalac options in build.sbt:

scalacOptions ++= Seq(
  "-Wvalue-discard", 
  "-Wnonunit-statement", 
  "-Wconf:msg=(discarded.*value|pure.*statement):error",
),

Expected result

Should cause compiler error: discarded non-Unit value of type Unit < (kyo.IO & kyo.Abort[java.io.IOException]) (If the defer block in runInner is replaced with a direct call to Console.println, this is what happens)

Actual result

No compiler error or warnings, and the application runs without displaying anything message

[johnhungerford]

Workaround: annotating runInner as Any < ... will cause the compiler to catch the error. It seems to be a problem only for unit values. Anyone working with kyo-direct might consider using Any in place of Unit until some solution is found.

[fwbrasil]

/bounty 100

[algora-pbc]

💎 $100 bounty • Kyo

Steps to solve:

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[fwbrasil]

I took a look at this and couldn't find a way to fix it. It seems the compiler just bypasses the check. cc/ @rssh