Suggest using let-chains

[nickdrozd]

What it does

2024 edition introduces let-chains (rust-lang/rust#53667). It would be cool if Clippy could identify places where this feature could be used. Maybe autofix too?

Advantage

• Less nesting
• Less logical complexity

Drawbacks

No response

Example

if let Some(x) = f() {
    if g(x) {
        dbg!(x)
    }
}

Could be written as:

if let Some(x) = f() && g(x) {
    dbg!(x)
}

[y21]

#14481 implemented this as an extension to the collapsible_if lint.

(It's not on nightly yet though, there's been some issues with the clippy->rust sync so the component has been behind this repo for a few weeks now, but it should be soon)

Clippy output for the example snippet

warning: this `if` statement can be collapsed
 --> x.rs:5:5
  |
5 | /     if let Some(x) = f() {
6 | |         if g(x) {
7 | |             dbg!(x);
8 | |         }
9 | |     }
  | |_____^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_if
  = note: `#[warn(clippy::collapsible_if)]` on by default
help: collapse nested if block
  |
5 ~     if let Some(x) = f()
6 ~         && g(x) {
7 |             dbg!(x);
8 ~         }
  |

[mi2ebi]

@y21 shouldn't the final brace be unindented one level? or is that not really something clippy can do? /genq

[nickdrozd]

@y21 Cool, feel free to close this issue, or leave it open for tracking.