<!--
Thank you for contributing to Ruff/ty! To help us out with reviewing,
please consider the following:
- Does this pull request include a summary of the change? (See below.)
- Does this pull request include a descriptive title? (Please prefix
with `[ty]` for ty pull
requests.)
- Does this pull request include references to any relevant issues?
-->
## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
This PR fixes#19047 / the [isinstance-type-none
(FURB168)](https://docs.astral.sh/ruff/rules/isinstance-type-none/#isinstance-type-none-furb168)
tuple false positive by adding a check if the tuple is empty to the
code. I also noticed there was another false positive with the other
tuple check in the same function, so I fixed it the same way.
`Union[()]` is invalid at runtime with `TypeError: Cannot take a Union
of no types.`, but it is accepted by `basedpyright`
[playground](https://basedpyright.com/?pythonVersion=3.8&typeCheckingMode=all&code=GYJw9gtgBALgngBwJYDsDmUkQWEMoCqKSYKAsAFAgCmAbtQIYA2A%2BvAtQBREkoDanAJQBdQUA)
and is equivalent to `Never`, so I fixed it anyways. I'm getting on a
side tangent here, but it looks like MyPy doesn't accept it, and ty
[playground](https://play.ty.dev/c2c468b6-38e4-4dd9-a9fa-0276e843e395)
gives `@Todo`.
## Test Plan
<!-- How was it tested? -->
Added two test cases for the two false positives.
[playground](https://play.ruff.rs/a53afc21-9a1d-4b9b-9346-abfbeabeb449)
## Summary
Implement
[`no-isinstance-type-none`](https://github.com/dosisod/refurb/blob/master/refurb/checks/builtin/no_isinstance_type_none.py)
as `isinstance-type-none` (`FURB168`).
Auto-fixes calls to `isinstance` to check if an object is `None` to a
`None` identity check. For example,
```python
isinstance(foo, type(None))
```
becomes
```python
foo is None
```
Related to #1348.
## Test Plan
`cargo test`
---------
Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>
GiGaGon
InSync
Tom Kuson