Main.scala

object A {
  trait B {
    case class C(a1: Int, a2: Option[Int])
  }

  object D extends B
}

object Main {
  def main(args: Array[String]): Unit = {
    println(scala.util.Properties.versionString)
    val c = classOf[A.D.C].getConstructors.head
    println(c.getGenericParameterTypes.toList)
    println(c.getParameters.toList)

    // 2.13.0-RC1, 2.12.8
    // List(interface A$B, int, scala.Option<java.lang.Object>)
    // List(final A$B $outer, final A$B a1, final int a2)

    // 2.13.0-RC2
    // List(int, scala.Option<java.lang.Object>)
    // List(final A$B $outer, final int a1, final scala.Option<java.lang.Object> a2)
  }
}