I've been typing SQLAlchemy for some months now and there's lots of scenarios where if you end up on mypy's issue tracker (which is very often), you will see "oh use a #type: ignore to deal with this occasional use case" as official advice. And here we see a compiler that considers all "# type: ignore" to be bugs and will eventually refuse to compile them. That's simply not realistic for the way Python typing works right now and I am skeptical.