gistfile1.txt

// simplest thing
trait ViewImpl {
  def de(items: List[OBItem]): Omnibox[OBItem]
}

// if you want a tighter bound on the result than OBItem, like if all the elements of the list are of type SomeItem, and you want the result to also be of type Omnibox[SomeItem]
trait ViewImpl {
  def de[OB <: OBItem](items: List[OB]): Omnibox[OB]
}