I define case class in spark-shell or scala-shell, and found its constructor signature is changed, there's one extra parameter $iw added, what is that? why that happens? This issue caused me unable to create new instance via its constructor in reflection
scala> case class People(id:Int, name: String)
class People
scala> classOf[People].getDeclaredConstructors.head
val res0: java.lang.reflect.Constructor[_] = public People($iw,int,java.lang.String)
This is expected behavior in both scala-shell and spark-shell after scala 2.12. If you just use spark-shell for quick experiments, you could try spark 2.4 which relies on scala 2.11. For prod, you still can build your package by using relection on case case contructors.
For more details, please refer
snakeyaml and spark results in an inability to construct objects