Regression in apache/incubator-pekko - invalid type inference

[WojciechMazur]

Based on Open CB failure for apache/incubator-pekko - build logs

Compiler version

Since 3.4.0-RC1-bin-20231113-0dfe593-NIGHTLY

Bisect points to a196167

Minimized code

import java.util.concurrent.CompletionStage
import scala.concurrent.Future


trait ActorRef[-T]{
   def ask[Res](replyTo: ActorRef[Res] => T): Future[Res] = ???
}


implicit final class FutureOps[T](private val f: Future[T]) extends AnyVal {
  def asJava: CompletionStage[T] = ???
}

class AskPattern[Req, Res] {
  val actor: ActorRef[Req] = ???
  val messageFactory: ActorRef[Res] => Req = ???

  def failing(): CompletionStage[Res] = actor.ask(messageFactory.apply).asJava
  def workaround1(): CompletionStage[Res] = actor.ask[Res](messageFactory.apply).asJava
  def workaround2(): CompletionStage[Res] = actor.ask(messageFactory).asJava

  val jMessageFactory: java.util.function.Function[ActorRef[Res], Req] = ???
  def originalFailingCase(): CompletionStage[Res] = actor.ask(jMessageFactory.apply).asJava
}

Output

-- [E007] Type Mismatch Error: /Users/wmazur/projects/dotty/bisect/main.scala:18:72 
18 |  def failing(): CompletionStage[Res] = actor.ask(messageFactory.apply).asJava
   |                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |                     Found:    java.util.concurrent.CompletionStage[Any]
   |                     Required: java.util.concurrent.CompletionStage[Res]
   |
   | longer explanation available when compiling with `-explain`
-- [E007] Type Mismatch Error: /Users/wmazur/projects/dotty/bisect/main.scala:23:84 
23 |  def originalFailingCase(): CompletionStage[Res] = actor.ask(messageFactory.apply).asJava
   |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |                     Found:    java.util.concurrent.CompletionStage[Any]
   |                     Required: java.util.concurrent.CompletionStage[Res]
   |

Expectation

Should compile

[WojciechMazur]

Another reproduction of code that started to fail since the same commit

import scala.util.{Try, Success, Failure}

trait ActorRef[-T]
trait ActorContext[T] {
  def ask[Req, Res](target: ActorRef[Req], createRequest: ActorRef[Res] => Req)(
      mapResponse: Try[Res] => T
  ): Unit
}

@main def Test =
  val context: ActorContext[Int] = ???
  val askMeRef: ActorRef[Request] = ???

  case class Request(replyTo: ActorRef[Int])

  context.ask(askMeRef, Request.apply) {
    case Success(res) => res // error: expected Int, got Any
    case Failure(ex)  => throw ex
  }

[WojciechMazur]

Yet another minimisation based on creativescala/doodle Open CB logs

trait IO[A]:
  def map[B](f: A => B): IO[B] = ???

trait RenderResult[T]:
  def value: T

def IOasync[T](f: (Either[Throwable, T] => Unit) => Unit): IO[T] = ???

def render[T]: IO[T] = {
  def register(cb: Either[Throwable, RenderResult[T]] => Unit): Unit = ???
  IOasync(register).map(_.value) // map should take RenderResult[T], but uses Any
}

yields:

[error] ./main.scala:11:25
[error] value value is not a member of Any
[error]   IOasync(register).map(_.value)
[error]