type was inferred to be AnyVal/Any; this may indicate a programming error.

[He-Pin]

Reproduction steps

Scala version: 2.3.10

ByteString.empty.indexOf(5) should ===(-1)

Problem

[10-09 04:53:38.583] [error] /home/runner/work/akka/akka/akka-actor-tests/src/test/scala/akka/util/ByteStringSpec.scala:634:24: a type was inferred to be `AnyVal`; this may indicate a programming error.
[10-09 04:53:38.583] [error]       ByteString.empty.indexOf(5) should ===(-1)

and

[10-09 04:53:37.041] [error] /home/runner/work/akka/akka/akka-actor-tests/src/test/scala/akka/util/ByteIteratorSpec.scala:24:23: a type was inferred to be `AnyVal`; this may indicate a programming error.
[10-09 04:53:37.042] [error]       freshIterator().indexOf(0x10, 3) should be(5)

[10-09 04:53:28.219] [error] /home/runner/work/akka/akka/akka-actor-tests/src/test/scala/akka/actor/FSMActorSpec.scala:256:19: a type was inferred to be `Any`; this may indicate a programming error.
[10-09 04:53:28.219] [error]         .parseMap(Map("akka.loglevel" -> "DEBUG", "akka.actor.debug.fsm" -> true).asJava)
[10-09 04:53:28.220] [error]                   ^
[10-09 04:53:30.674] [error] /home/runner/work/akka/akka/akka-actor-tests/src/test/scala/akka/actor/dispatch/ActorModelSpec.scala:235:32: a type was inferred to be `Object`; this may indicate a programming error.
[10-09 04:53:30.675] [error]             Option(dispatcher).getOrElse(this).getClass,

from : https://github.com/akka/akka/actions/runs/3212916837/jobs/5252192044

akka/akka#31648

1. the indexOf method returns Int , so should not get an error.
   
   

Explain how the above behavior isn't what you expected.

compiles correctly.

[som-snytt]

-Vprint:typer says

      ByteIteratorSpec.this.convertToAnyShouldWrapper[Int](freshIterator().indexOf[AnyVal](32))((Position.apply("ByteIteratorSpec.scala", "Please set the environment variable SCALACTIC_FILL_FILE_PATHNAMES to yes at compile time to enable this feature.", 19): org.scalactic.source.Position), scalactic.this.Prettifier.default).should(ByteIteratorSpec.this.be.apply(0));

for

[error] .../akka/akka-actor-tests/src/test/scala/akka/util/ByteIteratorSpec.scala:19:23: a type was inferred to be `AnyVal`; this may indicate a programming error.
[error]       freshIterator().indexOf(0x20) should be(0)

where

  def indexOf(elem: Byte): Int = indexOf(elem, 0)
  def indexOf(elem: Byte, from: Int): Int = indexWhere(_ == elem, from)

  override def indexOf[B >: Byte](elem: B): Int = indexOf(elem, 0)
  override def indexOf[B >: Byte](elem: B, from: Int): Int = indexWhere(_ == elem, from)

Probably indexOf(0x20: Byte). Otherwise the arg is an Int. This is why we need byte literals.

Edit: or, of course, explicit type arg.

[som-snytt]

I see that the ticket under which the behavior was tweaked explicitly mentions ScalaTest in this regard.

#12441

[som-snytt]

Looked at another example in ActorModelSpec, which is also a classic.

Option(dispatcher).getOrElse(this).getClass

is

scala.Option.apply[akka.dispatch.MessageDispatcher](dispatcher).getOrElse[Object](this).getClass()

but could be expressed

Option(dispatcher).map(_.getClass).getOrElse(getClass)

but I guess after you see it, you might prefer the explicit getOrElse[Object].

scala.Option.apply[akka.dispatch.MessageDispatcher](dispatcher).map[Class[_ <: akka.dispatch.MessageDispatcher]](((x$1: akka.dispatch.MessageDispatcher) => x$1.getClass())).getOrElse[Class[_1] forSome { type T <: akka.dispatch.MessageDispatcher; type _1 >: T with T <: Object }](ActorModelSpec.this.getClass())

It would be nice not to warn if a universal method is invoked on the inferred type somewhere.