Void

Scalqa/Source supports a concept of "void object" ("empty object"), which can be defined for any type. This is similar to 'Null Object Pattern'

Unlike 'null', void object can have X invoked, getting some behavior pertinent to 'voidness'

Examples:

 - Void [[~.AbstractTrait]] is a singleton object of empty stream, which can be re-used for any type
 - Void [[?]], is a singleton optional value with no value, which can be re-used for any type
 - Void String, is a string of zero length, which can be re-used for String type instead of null

Void objects have standard way to declare their voidness mixing this trait. Alternatively, Able.Void trait can be mixed and isVoid test added explicitly

Types with void values have to define implicit conversions from \/

    class Foo

    object Foo{
      val void = new Foo with Void

      implicit def xxRequest(inline v: \/) = void
    }

    var v: Foo = \/   // Standard void assignment

A standard way to test for non voidness is Any.^ method