square/dagger — pull request #65 by cgruber (2012-10-17 04:30:30+00:00)
Title: Make UNRESOLVED Binding be effectively a null object, and use it polymorphically.

Make UNRESOLVED Binding be effectively a null object, and use it polymorphically. Also, make the Binding class abstract, to prevent anyone from instantiating it unintentionally and getting run-time unimplemented exceptions.