Are you sure it’ll be awful? Sorbet (https://sorbet.org/) is pretty popular already. It can statically check your whole project and dynamically check it at runtime. It also doesn’t add that much overhead so I’m not sure what you’re on about...
Not sure what Ruby core will do, but Sorbet will type everything as T.untyped in the absence of type hints. Libraries can progressively provide rbi files to add first class type support though.
Sorbet was developed before the details of the new Ruby type system were locked in. They’re working on providing some convergence in upcoming releases.
