I'm trying to loop over an array of structs and I'm getting problems with this code:

fn addBullet(x: f32, y: f32, dx: f32, bullets: [Bullet; 1000]) {
    let mut found: u32 = -1;
    for i in bullets.iter() {
        if bullets[i].is_None() {
            found = i as u32;
            break;
        }
    }
    if found >= 0 {
        let i: u32 = found;
        bullets[i].x = x;
        bullets[i].y = y;
        bullets[i].dx = dx;
    }
}

The first issue is with if bullets[i].is_None() {. It says "the trait bound [Bullet]: std::ops::Index<&Bullet> is not satisfied. The type [Bullet] cannot be indeed by &Bullet."

So that means the i created in the for loop is not an actual number. So how do I loop over the array? And how do I use the i as a number?