This maintains proposals for changes and user-visible enhancements to the Swift Programming Language. - swift-evolution/proposals/0244-opaque-result-types.md at b1caeccf5d273a1cc53b331d41ea169f7729...

it’s reassuring to know that the folks driving changes in Swift have a solid background in language design, and that they’re thinking about all manner of hard problems in order to make our lives easier. However, it makes me worry that people might be missing out on a truly exciting conversation about what might be coming in a future Swift version. The reason for the label “reverse generics” is that the flow of information is backwards from the existing system. Where right now, the caller binds generic types as it calls a function, the proposal would have the function itself bind the return types and pass concrete values back out.

“@jasdev @mbrandonw We still need to bind Outer to something to use it at a call site and ground the type. Any remaining generic allows us to create different types, like Email and Email, which might be totally what we want! But they’re diff types.”