The type checker implementations (eg; Steep, Sorbet) should throw an error at `return 42`. If `some_function_that_might_not_be_declared_in_an_rbs_file` is not k

The type checker implementations (eg; Steep, Sorbet) should throw an error at `return 42`. If `some_function_that_might_not_be_declared_in_an_rbs_file` is not known, the behavior may be configurable – it could be assumed to be something like `any` or assumed to be unsafe, and error until you declare that function. I think Sorbet has this configurability today, and I'm not sure about Steep's behavior. Steep: https://github.com/soutaro/steep https://github.com/soutaro/steep Sorbet: https://sorbet.org https://sorbet.org