Add support for NoReturn in auto-return-typing

[charliermarsh]

Summary

Given a function like:

def func(x: int):
    if not x:
        raise ValueError
    else:
        raise TypeError

We now correctly use NoReturn as the return type, rather than None.

Closes #9201.

[github-actions]

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[tooruu]

Does this use typing.Never in Python 3.11+?

[max-muoto]

Does this use typing.Never in Python 3.11+?

They're effectively identical in regards to type-checkers. Pyright (for Python 3.11+) infers the correct return type for a function like the one given in the example as NoReturn. typing.Never is used as a bottom type in situations like this:

def int_or_str(arg: int | str) -> None:
    never_call_me(arg)  # type checker error
    match arg:
        case int():
            print("It's an int")
        case str():
            print("It's a str")
        case _: # type checkers considers this unreachable
            never_call_me(arg)  # Pyright would say `arg` is of type `Never`.

[tooruu]

Does this use typing.Never in Python 3.11+?

They're effectively identical in regards to type-checkers. Pyright (for Python 3.11+) infers the correct return type for a function like the one given in the example as NoReturn. typing.Never is used as a bottom type in situations like this:

def int_or_str(arg: int | str) -> None:
    never_call_me(arg)  # type checker error
    match arg:
        case int():
            print("It's an int")
        case str():
            print("It's a str")
        case _: # type checkers considers this unreachable
            never_call_me(arg)  # Pyright would say `arg` is of type `Never`.

Official Python docs state that starting in 3.11 typing.Never should be used instead of typing.NoReturn. Looks like this has been addressed by #9213.