Support both __add__ and __radd__ between two generic parameters. #1325

import datetime
from typing import Any
from typing import Generic
from typing import Self
from typing import TypeVar

T = TypeVar("T")


class Foo(Generic[T]):
    value: T

    def __init__(self, value: T) -> None:
        self.value = value

    def baz(self, bar: Any) -> Self:
        value: T = self.value + bar
        return self.__class__(value)


fd: Foo[datetime.date] = Foo(datetime.date.today())
fd = fd.baz(datetime.timedelta(days=1))

fi: Foo[int] = Foo(5)
fi = fi.baz(1)