-Wunused gives warnings to values used in annotations

[markehammons]

Compiler version

3.3.0-RC2

Minimized code

import org.openjdk.jmh.annotations.*, Mode.{SingleShotTime, Throughput}
import java.util.concurrent.TimeUnit

@State(Scope.Thread)
@BenchmarkMode(Array(Throughput, SingleShotTime))
@Fork(
  jvmArgsAppend = Array(
    "--enable-preview",
    "--enable-native-access=ALL-UNNAMED"
  )
)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
class Test

https://scastie.scala-lang.org/W9ZhbHhJTr2zjkBC5FwUXQ

Output

unused imports for singleshot time, throughput, and TimeUnit

Expectation

These are clearly used.

[jchyb]

Minimized:

import scala.collection.immutable.HashMap
import scala.annotation.StaticAnnotation

class ExampleAnnotation(val a: Object) extends StaticAnnotation

@ExampleAnnotation(new HashMap())
class Test

shows:

-- Warning: a.scala:1:34 -------------------------------------------------------
1 |import scala.collection.immutable.HashMap
  |                                  ^^^^^^^
  |                                  unused import

[kyri-petrou]

Not sure if related, but same issue occurs for imports used alongside the derives keyword. e.g.,

import io.circe.generic.semiauto.*
import io.circe.Codec

final case class Foo(foo: String) derives Codec.AsObject

[carlosedp]

I'm also seeing unused warning when using annotations on 3.3.0-RC3:

import zio.*
import zio.temporal.*
// import zio.temporal.{workflowInterface, workflowMethod} // same warning using like this

// This is our workflow interface
@workflowInterface
trait EchoWorkflow {

  @workflowMethod
  def echo(str: String): String
}

❯ ./mill hello.compile
Compiling /Users/cdepaula/repos/scala-playground/zio-temporal-hello/build.sc
[34/34] hello.compile
[info] compiling 5 Scala sources to /Users/cdepaula/repos/scala-playground/zio-temporal-hello/out/hello/compile.dest/classes ...
[error] -- Error: /Users/cdepaula/repos/scala-playground/zio-temporal-hello/shared/src/EchoWorkflow.scala:2:20
[error] 2 |import zio.temporal.*
[error]   |                    ^
[error]   |                    unused import
[error] one error found
1 targets failed
hello.compile Compilation failed

Same happens with no "*" imports for these annotations like comment in code above.