## Summary
This looks like it should fix the errors that we've been seeing in sympy
in recent mypy-primer runs.
## Test Plan
I wasn't able to reproduce the sympy failures locally; it looks like
there is probably a dependency on the order in which files are checked.
So I don't have a minimal reproducible example, and wasn't able to add a
test :/ Obviously I would be happier if we could commit a regression
test here, but since the change is straightforward and clearly
desirable, I'm not sure how many hours it's worth trying to track it
down.
Mypy-primer is still failing in CI on this PR, because it fails on the
"old" ty commit already (i.e. on main). But it passes [on a no-op PR
stacked on top of this](https://github.com/astral-sh/ruff/pull/20370),
which strongly suggests this PR fixes the problem.
82796df9b5