Clippy hangs on `.unwrap().unwrap() as usize` on nightly

[stevenengler]

Summary

When running cargo clippy on a library with the following code using rust nightly, it hangs and never completes. The clippy process CPU usage is at 100% of a core while it's running.

If anyone has a better title, please update it since I'm not sure exactly what's causing the bug.

Reproducer

fn _foo() -> usize {
    let bar: Result<Option<i64>, u32> = Ok(Some(10));
    bar.unwrap().unwrap() as usize
}

It hangs with the output:

    Checking clippy-bug v0.1.0 (/tmp/clippy-bug)
    Building [                             ] 0/1: clippy-bug

(I've waited 5 minutes, so I'm assuming it would hang forever.)

Version

rustc 1.79.0-nightly (eb45c8444 2024-03-17)
binary: rustc
commit-hash: eb45c844407968ea54df0d9870ebce9e3235b706
commit-date: 2024-03-17
host: x86_64-unknown-linux-gnu
release: 1.79.0-nightly
LLVM version: 18.1.2

Additional Labels

No response

[Centri3]

Can't reproduce this on beta (currently 1.77.0-beta.9. The only commit since then is fc8f662

(This commit isn't in beta despite it being a few days ago, I think.)

[stevenengler]

Can't reproduce this on beta (currently 1.77.0-beta.9. The only commit since then is fc8f662

(This commit isn't in beta despite it being a few days ago, I think.)

This can also be seen on the rust playground, where clippy works when set to "beta" but not "nightly".

[Centri3]

Oh yeah I know, this is an issue, I was saying that it's something new since beta (so that PR I think)

[y21]

Looks like it gets stuck in this loop
https://github.com/rust-lang/rust-clippy/blob/master/clippy_lints/src/casts/cast_sign_loss.rs#L135 (#12126)

This should probably reassign expr to actually peel off the method calls and not get stuck on the same expr forever?

[stevenengler]

Thanks!