trait TaskDef {
    type Arguments <: AnyVal
    type Result <: AnyVal
}
 
trait TaskInst[DefT <: TaskDef] {
    def definition: DefT
    def arguments: DefT#Arguments
}
 
object Main extends App {
	object MyTaskDef extends TaskDef {
		override type Arguments = Int
		override type Result = Double
	}
	object MyTaskInst extends TaskInst[MyTaskDef.type] {
		override def definition = MyTaskDef
		override def arguments = 42
	}
	println(MyTaskInst.definition)
	println(MyTaskInst.arguments)
}

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