This library introduces a generic Interval type that intends to unify Swift's Range and its likes. The current implementation is spun out of Swift's draft pull request #32865, with some bug fixes, and a lot more test cases.
Interval is under active development. At the moment, I'm working on bringing the test coverage to 100%. Support for interval arithmatics and set algebra are in the plan. I'm also exploring ways of incorporating compile-time type chedking into interval iteration without separating interval representation into multiple types.