Type parameters & datetime.replace

[kellerza]

PEP 695, Python 3.12+

This function gives 2 errors

def strip_utc[T](obj: T) -> T:
    """Remove UTC from datetime objects inside lists or dicts."""
    if isinstance(obj, datetime):
        return obj.replace(tzinfo=None)  # <<<<<<<<<<<<<<<<
    if isinstance(obj, list):
        return cast(
            T,
            [strip_utc(i) if isinstance(i, list | dict | datetime) else i for i in obj],
        )
    if isinstance(obj, dict):
        res = dict.copy(obj)
        for k, v in res.items():
            if isinstance(v, list | dict | datetime):
                res[k] = strip_utc(v)
        return res  # <<<<<<<<<<<<<<<<<<<<<<<<<<
    return obj

error: Incompatible return value type (got "datetime", expected "T")  [return-value]
error: Incompatible return value type (got "dict[Any, list | dict | datetime]", expected "T")  [return-value]

[davidhalter]

I quickly checked this with Mypy and I tend to agree (the server is currently down, I hope it's not permanent):

https://mypy-play.net/?mypy=latest&python=3.12&gist=20c71b63151bab98d71439f3b095ba8f

y.py:18: error: Incompatible return value type (got "dict[Any, Any]", expected "T")  [return-value]

Dict is not guaranteed to be the same type as the TypeVar (when returned) and I'm not sure I want to change that.