Previously this didn't raise an error. Now it will:
```python
from collections.abc import Callable
isinstance(int, list | Callable[..., str])
```
Also added tests in Union since there were previously none for stuff like ``isinstance(list, list | list[int])`` either.
Backport to 3.9 not required.
Automerge-Triggered-By: GH:gvanrossum
Use Py_ssize_t type rather than int, to store lengths in
unionobject.c. Fix the warning:
Objects\unionobject.c(205,1): warning C4244: 'initializing':
conversion from 'Py_ssize_t' to 'int', possible loss of data
Use Py_ssize_t type rather than int, to store lengths in
unionobject.c. Fix warnings:
Objects\unionobject.c(189,71): warning C4244: '+=':
conversion from 'Py_ssize_t' to 'int', possible loss of data
Objects\unionobject.c(182,1): warning C4244: 'initializing':
conversion from 'Py_ssize_t' to 'int', possible loss of data
Objects\unionobject.c(205,1): warning C4244: 'initializing':
conversion from 'Py_ssize_t' to 'int', possible loss of data
Objects\unionobject.c(437,1): warning C4244: 'initializing':
conversion from 'Py_ssize_t' to 'int', possible loss of data
Ken Jin
Neil Schemenauer
Serhiy Storchaka
Victor Stinner
Maggie Moss