Currently, the overload order is:

However, both the c-module and the fallback pydatetime first check if other is a datetime:

    def __sub__(self, other):
        "Subtract two datetimes, or a datetime and a timedelta."
        if not isinstance(other, datetime):
            if isinstance(other, timedelta):
                return self + -other
            return NotImplemented

https://github.com/python/cpython/blob/c7d68f907ad3e3aa17546df92a32bddb145a69bf/Lib/_pydatetime.py#L2235-L2257

https://github.com/python/cpython/blob/1198076447f35b19a9173866ccb9839f3bcf3f17/Modules/_datetimemodule.c#L5608

So shouldn't the overload order be vice versa?

Also, I noticed that at runtime, timedelta has __rdivmod__, __rmod__ and datetime has __rsub__, which are missing in the stub. But I guess this is because the pure python fallback doesn't have them.