def backward[E <: Element](condition: E => Boolean)(implicit manifest: Manifest[E]): E = {
      previous match {
        case null => null
        case element if (matchesManifest(previous, manifest)) => element.asInstanceOf[E]
        case element => element.hierarchy.backward[E](condition)(manifest)
      }
    }

[info] Compiling 1 Scala source to Z:\programming\sgine\core\target\scala-2.9.1\classes...
[error] Z:\programming\sgine\core\src\main\scala\org\sgine\hierarchy\Element.scala:45: type mismatch;
[error]  found   : Null(null)
[error]  required: E
[error]         case null => null
[error]                      ^
[error] one error found