How to handle typechecker specific bugs

In the past, we've worked around typechecker bugs and missing features in typeshed. But as the amount of typecheckers grows and type stubs are used for more that just type checking, I don't think we can work around any bug or missing feature of every typechecker in typeshed, especially if this means regressing our stubs. Not only is this more maintainer work and it gets hard to remember which typechecker has which bug, it also means that users of bug-free typecheckers and other software will still be affected by those bugs.

I think that we should still accommodate very impactful bugs and missing major features (per our "tracking" bugs) for the "big four" mypy, pytype, pyright, and pyre. We also need to work around some bugs due to our tests. But apart from that, we should work with typecheck authors (and there is some overlap here, of course) to come up with a solution.

Regarding stdlib stubs, I believe one option is that typecheckers ship with a customized version of typeshed for major problems. Apart from that, it's always possible for users to # type: ignore a problem with a specific typechecker.

Start by reading the issue discussion and the referenced tracking bugs for mypy, pytype, pyright, and pyre. This is a policy/design question rather than a localized implementation task; it is done only when maintainers and typechecker authors agree on how major bugs and missing features should be handled.