unreachable code isn't type checked

[DetachHead]

foo: str

if isinstance(foo, str):
    ...
else:
    asdf: list[str] = "" # no error

https://mypy-play.net/?mypy=master&python=3.10&gist=98cc704dbc9936fa1c3801984cd631fd

my use case is an assert_unreachable function:

def assert_unreachable(msg: str):
    raise AssertionError(msg)

foo: str

if isinstance(foo, str):
    ...
else:
    # no error even though the msg argument was not provided
    assert_unreachable() #type:ignore[unreachable]

[hauntsaninja]

Yeah, this is intentional. https://mypy.readthedocs.io/en/stable/common_issues.html#unreachable-code
I think in practice basically all warnings mypy would give if it didn't do this would end up being false positives.

[KotlinIsland]

@hauntsaninja Those docs don't really explain why "this would end up being false positives", only showing very obvious true positives being ignored.