The goal of this document is to provide a comprehensive view of what value subtyping might look like in Swift and demonstrate how generalized enums play a significant role in this future.
Note: All syntax used in this document that is not currently valid Swift syntax is only intended to serve the purpose of demonstrating ideas and to serve as a point of reference for future proposals. The intent is not to propose that this exact syntax be used.
Acknowledgement: some of the ideas in this document have been inspired by Niko Matsakis' blog post exploring similar ideas in the context of Rust: http://smallcultfollowing.com/babysteps/blog/2015/08/20/virtual-structs-part-3-bringing-enums-and-structs-together/
