Iterating over an opened file should be strings/bytes

[jakebailey]

with open("something.txt") as f:
    for line in f:
        print(line)

line should be some text type. Iteration just needs to be specialized.

[MikhailArkhipov]

Since open is specialized to return TextIOWrapper, BufferedRandom, BufferedReader or BufferedWriter from io and that's in turn, exists in typeshed as

def __iter__(self) -> Iterator[str]: ...
def __next__(self) -> str: ...

We need to properly invoke __next__ and specialize Iterator in typing.