new lint: double reverse

[matthiaskrgr]

simple example:

let v: Vec<i32> = vec![4, 1, 4,3,5,6];
v.reverse();
v.reverse();
prinln!("{:?}", v);

example involving function:

pub fn main() {
   let mut v: Vec<i32> = vec![4, 1, 4,3,5,6];
   v.sort();
   let mut v2 = foo(v);
   v2.reverse();
   println!("{:?}", v2);
}

pub fn foo(a: Vec<i32>) -> Vec<i32> {
    let mut b = a;
    b.reverse();
    b
}

[oli-obk]

idk, feels a little contrived. Also, is it guaranteed to be idempotent? For fancy impls of PartialOrd we might not actually get back the same result and users might be using it for that.

[matthiaskrgr]

Imo double reverse is still worth investigating, so this lint is not meant as "look, this is wrong!" but rather as "hey, this is suspicious, maybe check it out?".
Could be a pedantic or nursery lint.