Private types can be inferred but not explicitly typed

Two examples:
https://scastie.scala-lang.org/wdskxrQQRbeB2ZHkDdXaoA

And
```scala
package factory{
  private [factory] class Factory
  object Factory{
    def f(): factory.Factory = new Factory()
  }
}
object G {
 //type annotation fails to compile!
  val f: factory.Factory = factory.Factory.f()
}
```