Mocking tagged types fails in Scala 3

[arteme]

If you want to discuss a new feature, please ignore/clear this form.

ScalaMock Version (e.g. 3.5.0)

6.0.0

Scala Version (e.g. 2.12)

3.4.2

Runtime (JVM or JS)

JVM

Please describe the expected behavior of the issue

Consider the following code:

import org.scalamock.scalatest.MockFactory
import org.scalatest.TestSuite

// macwire tagging
trait Tag[+U] extends Any { type Tag <: U }
type @@[+T,+U] = T with Tag[U]

implicit class Tagger[T](val t: T) extends AnyVal {
  @inline def taggedWith[U]: T @@ U = t.asInstanceOf[T @@ U]
}

// example
case class CacheApi()
trait SettingsCache
trait DataCache

case class Controller(settingsCache: CacheApi @@ SettingsCache)

// how this may be used in the real app
object RealContext {  
  val settingsCache: CacheApi @@ SettingsCache = CacheApi().taggedWith[SettingsCache] 
  val dataCache: CacheApi @@ DataCache = CacheApi().taggedWith[DataCache]
  val contoller = Controller(settingsCache)
}

// how this is used in tests
trait TestContext extends MockFactory {
  this: TestSuite =>
  
  val controller = mock[Controller]
}

This code correctly mocks Controller in Scala 2.13, but fails in Scala 3 with a message:

Found:    @@
Required: CacheApi @@ SettingsCache

Scala 3 playground: https://scastie.scala-lang.org/mrSdYwvmSi2yz9daKC4neA
Scala 2.13 playground: https://scastie.scala-lang.org/jv7RKjqtTV2FUycZyME6MQ

[goshacodes]

Hi, thank you for reporting. It surely was supported in scala 2, but I'm not sure it should be fixed for scala 3, IMO you are doing something wrong.
You should mock interfaces not implementations.
Consider using Dependency Inversion principle and make your implementations depend on interfaces. It will make your test cases simpler and life easier.