@strawberry.field
def resolver_arguments(self, info: Info, date: datetime.date):
    [selected_field] = info.selected_fields
    assert type(date) == date
    assert selected_field.arguments["date"]) == date
    # ^^^ This fails when passing the `date` argument as part of the query
    #     It works when passing the argument via the variables.
    ...

@strawberry.input
class Obj:
    date: Optional[datetime.date] = None

@strawberry.type
class Query:
    @strawberry.field
    def typenames(self, info: Info, obj: Optional[Obj] = None):
        assert isinstance(obj, Obj)
        [field] = info.selected_fields
        assert isinstance(field.arguments["obj"], Obj)
        # ^^^ This always fails.