Question

If I could figure out how to “attach manifests back the generic call stack” (as Joshua writes about in section 7.2.2 of “Scala in Depth”), would that enable me to instantiate B along those lines?:

def m1[T](implicit m: Manifest[T]): T = m.erasure.newInstance.asInstanceOf[T]

class A {
  def m2[T](implicit m: Manifest[T]): T = m.erasure.newInstance.asInstanceOf[T]
  def inA() {
    m1[A]
    m2[A]
    m2[B] // Doesn't work...
  }
  class B
}

m1[A]
val a = new A
a.m2[A]
a.inA() // boom

Or do I need some view bound?

Answer 1

You cannot instantiate the inner class B like this, because the constructor of such inner classes secretly takes a reference to an object of the outer class. newInstance can only be called on classes that have a zero-argument constructor.