[Typing-sig] Re: seeking feedback on a proposed deprecation library to be used at type checking time (in pytype)

Following up this thread. Looks like we share a common interest in a decorator approach (though I haven't heard from mypy). And if we allow deprecating overloads (to deprecate parameters), I believe this covers the majority of the use cases and is a real improvement even without a `typing.Deprecated` type. If I want to formally propose this shared decorator, where should I start? Does it make sense for this decorator to live in the typing module? If not, where then? - Yilei