new lint [redundant_guards]

[Centri3]

Closes #7825, maybe somebody else can get the ranges lint in the comments?

changelog: New lint [redundant_guards]

[rustbot]

r? @Manishearth

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[Manishearth]

bouncing review to @blyxyas (if you're interested) cc @xFrednet

[blyxyas]

Yep, will review it! 🌵

[bors]

☔ The latest upstream changes (presumably #10934) made this pull request unmergeable. Please resolve the merge conflicts.

[blyxyas]

wow, I imagine this has been pretty hard to do. Pretty cool (and useful!) lint. Thanks! ❤️ (Some veeery minor nits)

[blyxyas]

Just noticed, we should probably put this in the matches group

[xFrednet]

@Alexendoo, do you maybe want to take over the after/co review with @blyxyas ? Then I would hand this PR over to you two :)

[Alexendoo]

Sure thing @xFrednet

[Centri3]

I've applied your suggestions minus ignoring or patterns, as that doesn't seem to work unfortunately.

[Alexendoo]

Thanks, just one last nit and then if you could squash the commits that'd be great

[bors]

☔ The latest upstream changes (presumably #10885) made this pull request unmergeable. Please resolve the merge conflicts.

[Alexendoo]

Thanks again! @bors r=Alexendoo,blyxyas

[bors]

📌 Commit 51b5772 has been approved by Alexendoo,blyxyas

It is now in the queue for this repository.

[bors]

⌛ Testing commit 51b5772 with merge df3804a...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Alexendoo,blyxyas
Pushing df3804a to master...

[jcamiel]

Hi, just upgraded to 1.73 and notice this new lint. I've upgraded my code and this snippet:

    let input = input.parse::<i32>().unwrap();
    match input {
        i if i == -1 => println!("-1"),
        i if i == 0 => println!("0"),
        i => println!("{i}")
    }

Triggers the following clippy warning:

warning: redundant guard
  --> src/main.rs:14:14
   |
14 |         i if i == 0 => println!("0"),
   |              ^^^^^^
   |

Fixing the snippet, I've now:

    let input = &args[1];
    let input = input.parse::<i32>().unwrap();
    match input {
        i if i == -1 => println!("-1"),
        0 => println!("0"),
        i => println!("{i}")
    }

And no more clippy warning!

I find it odd that the branch i if i == 0 triggers the lint but not the branch i if i == -1?

[Alexendoo]

Good catch, opened #11641 to cover that

I always forget that -1 isn't a literal, it's a unary operator applied to the literal 1