# Rust lang
## Topic B

We have implied a async function `bar` like:

async fn bar(a : &A, <other arguments>) -> Result<bool, anyhow::Error> {
    let handled_a = zoo(a); // zoo: fn(a: &a) -> usize
    //and there is no reference to a anymore
    /*
        <… code blocks …>
    */    
}

One day you found your code have broken because some updates on A made it lost its Sync trait and you can not make your code being complied.

Please fix your code without making more breakings.