You're missing an option which is type narrowing. Mypy as of 1.7 will recognize the tuple is proper if the length matches.
```python
def shift_week(dayofweek: int, week: T_week) -> T_week:
week_shifted: list[T_day] = []
week_shifted.extend(week[dayofweek:])
week_shifted.extend(week[:dayofweek])
rt = tuple(week_shifted)
assert len(rt) == 7
return rt
```
Using [TypeGuard](https://typing.python.org/en/latest/spec/narrowing.html#typeguard) seems to be tailored for this kind of problem.
```python
def has_7[T](tup: tuple[T, ...]) -> TypeGuard[tuple[T, T, T, T, T, T, T]]:
return len(tup) == 7
def shift_week(dayofweek: int, week: T_week) -> T_week:
week_shifted: list[T_day] = []
week_shifted.extend(week[dayofweek:])
week_shifted.extend(week[:dayofweek])
rt = tuple(week_shifted)
assert has_7(rt)
return rt
```
