Substrate

When you import a module into Swift code, you expect the result to be entirely additive. But as we’ll see, this isn’t always the case.

Ideas often get copied from well-known established projects into new projects with the background behind those decisions lost. Projects should have a "https://t.co/iLkkhljAHY" to lay out regretful design choices that can't be reversed for time, compatibility, etc. reasons— Joe Groff (@jckarter) January 14, 2019

This maintains proposals for changes and user-visible enhancements to the Swift Programming Language. - swift-evolution/0192-non-exhaustive-enums.md at main · apple/swift-evolution