Why does ClassCastException not happen in method?

object Test {
  trait MyType
  trait Ext extends MyType

  case class Non() extends MyType

  def caster[A <: MyType](a: MyType) = {
    a.asInstanceOf[A] // Exception should happen here, but doesn't
    println("This should never print")
  }

  def run() {
    val b = caster[Ext](Non())
    println("No exception yet.")
    val c = Non().asInstanceOf[Ext] // Exception is thrown if we do it directly here, which imo. should be exactly what we do above just via the method.

    println(b)
  }
}



/*

scala> Test.run
This should never print
No exception yet.
java.lang.ClassCastException: Test$Non cannot be cast to Test$Ext
    at Test$.run(<console>:53)
    at .<init>(<console>:40)

*/