I created https://discuss.python.org/t/finding-edge-cases-for-peps-484-463-and-649-typ... on behalf of the SC to help gather edge cases where the various approaches that PEPs have proposed will fail. Our hope is to get an overall picture of the trade-offs the various PEPs ask us to make. PLEASE DO NOT REPLY HERE! I'm reaching out to the typing SIG and Pydantic (at least) and it's much easier for others to log into discuss.python.org with a GitHub account than it is to sign up for this mailing list just to participate in this discussion.