Well, I still don't think this is exactly a pretty solution 😄 But it's ready for review -- and after the next pyright release, we'd be able to change them all to pyright: ignore[reportInvalidTypeVarUse] following the changes Eric just made in microsoft/pyright@f22576f.

I'll wait until the next pyright release (which I think will be tonight or tomorrow, according to the usual schedule) before landing this, since the next pyright release will presumably include microsoft/pyright@f22576f in it, and that will mean we can update all the ignores to reportInvalidTypeVarUse.

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

Ugh, what on earth is going on with third-party stubtest and GitHub Actions right now?

Stubtest failures are unrelated.