Are warnings ok when matching on generic types?

[goshacodes]

Compiler version

3.3.4
"-source:future-migration"

Hi. Compiler generates a warning on this code and I know why, but I'm not sure this is ok.
When you match on any - just cast to Matchable, but in this case it creates a mess with nested matches

Minimized code

sealed trait DiffResult extends Product with Serializable

case class DiffResultAdditional[T](value: T) extends DiffResult

case class Foo()

val diffResult: DiffResult = DiffResultAdditional(1)

diffResult match {
  case DiffResultAdditional(foo: Foo) => println("hello")
  case _ => println("boo")
}

Output

Compiles with warning:

pattern selector should be an instance of Matchable,
but it has unmatchable type T$1 instead

This works, but it makes your code a mess

diffResult match {
  case DiffResultAdditional(value) =>
     value.asInstanceOf[Matchable] match {
        case foo: Foo => println("hello")
     }
  case _ => println("boo")
}

Expectation

compiles without warning