Rust iterate over borrowed mutable reference

I wanted a function to control and change a vector in rust. Here is a simplified version:

fn foo(vec: &mut Vec<i32>) {
    for (i, element) in vec.iter().enumerate() {
        // Some checks here
        vec[(*element) as usize] = i as i32;
    }
}

fn main() {
    let mut bar: Vec<i32> = vec![1, 0, 2];
    foo(&mut bar);
}

This code does not compile because there is both an immutable and a mutable borrow of vec in foo. I tried getting around this by copying vec to a separate copy, which didn’t work and also wouldn’t have been very pretty. What is the correct way to do this?

>Solution :

You can avoid borrowing the whole Vec by using index access like this:

fn foo(vec: &mut Vec<i32>) {
    for index in 0..vec.len() {
        let element = vec[index];
        if element <= 0 {
            continue;
        }
        vec[index] = index as i32;
    }
}

fn main() {
    let mut bar: Vec<i32> = vec![1, 0, 2];
    foo(&mut bar);
    println!("{:?}", bar)
}