new lint to detect infinite loop

[J-ZhengLi]

closes: #11438

changelog: add new lint to detect infinite loop

I'll change the lint name. Should I name it infinite_loop or infinite_loops is fine? Ahhhh, English is hard...

[rustbot]

r? @Manishearth

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[matthiaskrgr]

What about loops that have todo!() / panic!() / unreachable() / assert!() in them? We have at least a test imo 🙂

[Manishearth]

r? @matthiaskrgr

might not have time to get around to this soon

[matthiaskrgr]

loops -> loop?
I think this reads a bit better.

[matthiaskrgr]

I also wondering about weird fn like

fn loopfn() -> Result<(), i32> {
    Ok(loop {})
}

afaik something like -> Result <!, i32> is not stabilized yet.

[J-ZhengLi]

I also wondering about weird fn like

Hmmm, Sorry I wasn't aware such cases, currently it would just prints help message suggesting adding a break condition...
What would be an ideal solution here 🤔 ?

[matthiaskrgr]

Sorry, was on holiday :)

If it only suggests adding break/return, I think it should be fine then.

Another scenario that just came to my mind now:

loop {
continue;
}

This does have some kind of "control flow" but in this case it still loops indefinitely.
The linkt would lint here as well, right? (which is the correct solution I think)

[J-ZhengLi]

Happy holiday 😄

As of your concern, yes it will lint, right now the visitor only looks for following occurrence in a loop block:

1. A return or a break
2. A function which never return, which was inspired be one of your early suggestion such as the one in panic!, unreachable!, also std::process::exit.

And if non of these could be find then... well, triggers the warning.

[matthiaskrgr]

Thanks!
@bors r+

[bors]

📌 Commit 758d0e8 has been approved by matthiaskrgr

It is now in the queue for this repository.

[bors]

⌛ Testing commit 758d0e8 with merge 2e96c74...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: matthiaskrgr
Pushing 2e96c74 to master...