Types that define `__iter__` with invalid signature are wrongly considered assignable to Iterable

[github-actions]

Run listed here: https://github.com/astral-sh/ty/actions/runs/16521468852

[AlexWaygood]

---- types::property_tests::stable::all_type_assignable_to_iterable_are_iterable stdout ----

thread 'types::property_tests::stable::all_type_assignable_to_iterable_are_iterable' panicked at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/quickcheck-1.0.3/src/tester.rs:165:28:
[quickcheck] TEST FAILED. Arguments: (EnumLiteral("unsafe"))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    types::property_tests::stable::all_type_assignable_to_iterable_are_iterable

A merge race between astral-sh/ruff#19187 and astral-sh/ruff#19328, I'd guess.

[sharkdp]

AlexWaygood self-assigned this

Thanks! Let me know if I can be of help

A merge race between astral-sh/ruff#19187 and astral-sh/ruff#19328, I'd guess.

A bit of a stretch to call it a race: the enum literals PR was merged 10 days ago 😜

[AlexWaygood]

the issue is fairly obvious: type(uuid.UUID.unsafe).__iter__ returns a bound attribute at runtime, and we recognize it as such in ty. But that's not sufficient for uuid.UUID.unsafe to be iterable, because the signature of type(uuid.UUID.unsafe).__iter__ doesn't match the signature specified by the typing.Iterable protocol (its Callable supertype is () -> Iterator rather than (self) -> Iterator).

So this is just a missing Protocol feature, and it's the next one I was going to tackle anyway now that astral-sh/ruff#19187 has landed!