while + next(generator, None) type Narrowing Issue

[sibarras]

Given a list list[T], when using the next function with the default None, the type should narrow down T | None to T, because while loop will catch the None type, and stop the iteration.

lst: list[T] = ...
gen = (v for v in lst)
while v := next(gen, None):
    # Here v should be T, but it's T | None
    print(v)  # This will never print None.

[sibarras]

It's working fine. My mistake.