I have an entry point wrapper that looks something like the trait listed below that is intended to expose a main for a java entry point if type T = Unit or an arbitrary return type T if the module is embedded:

trait RunWrapper[T] {
  def run(args : Array[String]) : T;
  def main(args : Array[String]) : T = {
    try { run(args) } finally { }
  }
}

// Entry point for java
object A extends RunWrapper[Unit] {
  def run(args : Array[String]) { println("the end") }
}

Unfortunately, I get this bytecode from the compiler (the same for both 2.8.1 and 2.9.0.1):

$ javap A
Compiled from "test.scala"
public final class A extends java.lang.Object{
public static final java.lang.Object main(java.lang.String[]);
public static final void run(java.lang.String[]);
}

Why do I get a return type of java.lang.Object, in this case, for main()? How do I get void in this scenario so that java will allow my to use A as an entry point?

However, if I define the following:

object B extends RunWrapper[Unit] {
def run(args : Array[String]) { println("the end") }
override def main(args : Array[String]) { try { run(args) } finally { } }
}

I get this:

$ javap B
Compiled from "test.scala"
public final class B extends java.lang.Object{
    public static final void main(java.lang.String[]);
    public static final void run(java.lang.String[]);
    public static final java.lang.Object main(java.lang.String[]);
}

So it seems override didn't override anything and the compiler doesn't complain or warn about this. Is this a boxing issue?