FP explicit_counter_loop: var incremented before usage

[matthiaskrgr]

I tried this code:

pub fn main() {
    let mut i = 0;
    let v = vec!["a", "b", "c"];
    for x in &v {
        i += 1;
        println!("{}", i)
    }
}

explicit_counter_loop will trigger here and suggest to use .iter().enumerate().
The problem is that we increment BEFORE using (and not at the end of the loop) so the first iteration will print 1 and not 0 as it would with .enumerate().
This newly suggested code is off by one as can be seen here:

pub fn main() {
    let mut i = 0;
    let v = vec!["a", "b", "c"];
    for (x, _) in v.iter().enumerate() {
        i += 1;
        println!("i is {} but x is {}", i, x)
    }
}

i is 1 but x is 0
i is 2 but x is 1
i is 3 but x is 2

clippy 0.0.212 (fb1dc34 2020-09-21)

[ebroto]

(I think suggestion-causes-error is intended for compiler errors and not semantic changes)

[ebroto]

Fixed by #6076