scala - Class type required but T found

Question

I can't create an actor for some reason (here is a simple version of my class hierarchy):

abstract class Class1[T <: Class2[_]: ClassTag] extends Actor {
   //....
   val res = List(1, 2, 3) map { x => context actorOf Props(new T(x)) } // error
}

abstract class Class2[U <: Class3 : ClassTag](a: Int) extends Actor { ... }
abstract class Class3(b: Int) extends Actor

But there is an error saying class type required but T found.

Answer 1

You can't call new T(x) with type parameter T. There could be no such constructor for T:

class WithoutSuchConstructor extends Class2[Class3](1)

You should specify method to create T explicitly:

abstract class Class1[T <: Class2[_]: ClassTag] extends Actor {
  //....
  def createT(i: Int): T
  val res = List(1, 2, 3) map { x => context actorOf Props(createT(x)) }
}

Alternatively:

abstract class Class1[T <: Class2[_]: ClassTag](createT: Int => T) extends Actor {
  //....
  val res = List(1, 2, 3) map { x => context actorOf Props(createT(x)) }
}