DWiki /
Feature Proposals
- Virtual Types
- /Variants?
- /LexicalClosures?
- /ConstantFunctions?
- /Metaprogramming?
- /Tuples?
- /PatternMatching?
- /Multimethods?
- /DynamicArrayInitializers?
Virtual Types are a superset of Type Covariance. Sather and Eiffel let you have Type Covariance without having placeholders for Virtual Types.
(From DWiki)