You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: while_let_on_iterator.rs
    path of file: ./repos/rust-clippy/tests/ui
    
    the code of the file until where you have to start completion: #![warn(clippy::while_let_on_iterator)]
#![allow(dead_code, unreachable_code, unused_mut)]
#![allow(
    clippy::equatable_if_let,
    clippy::manual_find,
    clippy::never_loop,
    clippy::redundant_closure_call,
    clippy::single_range_
    
fn issue6231() {
    // Closure in the outer loop, needs &mut
    let mut it = 1..40;
    let mut opt = Some(0);
    while let Some(n) = opt.take().or_else(|| it.next()) {
        while let Some(m) = it.next() {
            if n % 10 == 0 {
                break;
            }
            println!("doing something with m: {}", m);
        }
        println!("n still is {}", n);
    }
}