No problem; I wouldn't want changes to go through that haven't gotten the vetting that they need.

Diff from mypy_primer, showing the effect of this PR on open source code:

python-chess (https://github.com/niklasf/python-chess)
- chess/pgn.py:194: error: No overload variant of "iter" matches argument type "object"  [call-overload]
- chess/pgn.py:194: note: Possible overload variants:
- chess/pgn.py:194: note:     def [_SupportsNextT: SupportsNext[Any]] iter(SupportsIter[_SupportsNextT], /) -> _SupportsNextT
- chess/pgn.py:194: note:     def [_T] iter(_GetItemIterable[_T], /) -> Iterator[_T]
- chess/pgn.py:194: note:     def [_T] iter(Callable[[], _T | None], None, /) -> Iterator[_T]
- chess/pgn.py:194: note:     def [_T] iter(Callable[[], _T], object, /) -> Iterator[_T]

jax (https://github.com/google/jax)
- jax/_src/numpy/linalg.py:2087: error: Unused "type: ignore" comment  [unused-ignore]

xarray (https://github.com/pydata/xarray)
- xarray/core/dataset.py: note: In function "_get_chunk":
- xarray/core/dataset.py:280: error: Argument 1 to "difference" of "set" has incompatible type "object"; expected "Iterable[Any]"  [arg-type]
- xarray/core/dataset.py: note: At top level:

Given that mypy 1.12 uses unions for ternary, we could try this again after we update typeshed to mypy 1.12: https://github.com/python/typeshed/blob/main/requirements-tests.txt#L3

Given that mypy 1.12 uses unions for ternary, we could try this again after we update typeshed to mypy 1.12: https://github.com/python/typeshed/blob/main/requirements-tests.txt#L3

So, update first and see whether this helps? This doesn't seem time critical, as I don't think mypy 1.13 is going to be released in the next few days.

Funnily enough I think there will be a mypy 1.13 in the next few days, but it won't include a typeshed sync so we're fine :-)

So no time pressure, but would be good to confirm against mypy_primer. Merging this revert might still be the easiest way to do that. Or I guess seeing what it looks like on next typeshed sync to mypy

I kicked off a sync in python/mypy#17994

Looks like 1.12 does fix the issue with ternary expressions. The change for jax is still there.

I think that jax is surfacing the same underlying issue as ibis and psycopg in #12851 (comment) ; They all have the form func(*iterator), and have what I believe to be a correct warning going away when the class doesn't explicitly inherit from Iterator.

I don't have an opinion myself as to whether this should or shouldn't block the change.

I think this means we're all good and this revert can be closed :-)

Closing this out then.