[OK]
  def sum(a:Int,b:Int) = a+b

[NG]
  def sum(a:Int,b:Int) = a+b
  def sum(a:Int,b:String) = sum(a, b.toInt)

// (compile error)
//  overloaded method sum needs result type
//     def sum(a:Int,b:String) = sum(a, b.toInt)

[OK]
  def sum(a:Int,b:Int) = a+b
  def sum(a:Int,b:String):Int = sum(a, b.toInt)