type inference with cases. Why does this fail in scala 2.10.4? Is my logic wrong, or is the compiler not smart enough?

dependent_type_question.scala

sealed trait Key {
    type Inner
}

trait IntKey extends Key {
    type Inner = Int
}
trait StringKey extends Key {
    type Inner = String
}

// This should compile
object Key {
  def work(m: Key): m.Inner = m match {
   case i: IntKey => 1 //m in IntKey, and IntKey.Inner is Int, so we are good, right?
   case s: StringKey => "1"
  }
}


/* in scala 2.10.4 I see this:

test.scala:28: error: type mismatch;
 found   : Int(1)
 required: m.Inner
   case i: IntKey => 1
                     ^
test.scala:29: error: type mismatch;
 found   : String("1")
 required: m.Inner
   case s: StringKey => "1"
*/

I agree completely, and expect this will be improved in 3.0.