This code currently does not raise any issues:

```python
# contents of `ex.py`
from typing import ClassVar

a: ClassVar[int] = 1
def b(c: ClassVar[int]): ...
```

And then: 
1. Module: `python -c 'import ex; from typing import get_type_hints; print(get_type_hints(ex))'`
2. Function argument: `python -c 'import ex; from typing import get_type_hints; print(get_type_hints(ex.b))'`

It should not be allowed. Currently, the same with `from __future__ import annotations` does correctly raise `TypeError: typing.ClassVar[int] is not valid as type argument`

Related: https://github.com/python/cpython/pull/28279

I will send a PR with the fix shortly.