Why doesn't the Scala compiler infere the parameter type when subscribing to a Flowable with RxScala in Android?

Question

I'm trying to get started with RxJava2, RxScala and Android. I found a little example online which I tried to translate into Scala. But the Scala compiler can't figure out the type here:

MainIntent.scala:7:missing parameter type
[error]     actions("Button").subscribe(s => mainModel.resetText())

I'm also not sure what type is expected here. A Flowable[_ <: Any]]? How can I make it work?

This is the code:

import io.reactivex.functions.Consumer
import io.reactivex.Flowable


trait MainView {
  def getActions: Map[String, Flowable[_ <: Any]]

  def getConsumers: Map[String, Consumer[String]]
}

class MainIntent(mainView: MainView) {

  lazy val actions: Map[String, Flowable[_ <: Any]] = mainView.getActions
  lazy val mainModel = MainModel(mainView.getConsumers)

  def start(): Unit = {
    actions("Button").subscribe(s => mainModel.resetText())

    actions("EditText").subscribe(changedText => mainModel.changeText(changedText.toString))
  }
}

class MainActivity extends AppCompatActivity with MainView with TypedFindView {
  ...

  override def onCreate(savedInstanceState: Bundle): Unit = {
    ...
    new MainIntent(this).start()
  }

  def getActions(): Map[String, Flowable[_ <: Any]] = {
    Map("Button" -> RxView.clicks(button).toFlowable(BackpressureStrategy.DROP),
     "EditText" -> RxTextView.textChanges(editText).toFlowable(BackpressureStrategy.DROP))
  }

  ...
}