new lint: find length comparisons after access by index in ANDded if-chains

[matthiaskrgr]

What it does

Check for code like

fn a(v1: Vec<_>, v2: Vec<_>, x: usize) {
  if v1[x] == v2[x] &&
     v1.len() == v2.len() {}
}

The length-check is probably intended to guard against index-out-of-bounds access however it was (most likely mistakenly) placed AFTER the access by index. It should be at the front.

Categories (optional)

• Kind: correctness

Inspired by #5780 and #5784

[GuillaumeGomez]

I would even suggest to use get() instead. :)