Code shared from the Rust Playground

playground.rs

struct Foo<'a> {
    bar: &'a i32
}

/*impl<'a, 'b: 'a> Foo<'b> {
    fn new(bar: &'b i32) -> Self {
        Foo { bar }
    }
    
    fn qux(&'a mut self) -> &'b i32 {
        self.bar
    }
}*/

impl<'a> Foo<'a> {
    fn qux(&'a mut self) -> &'a i32 {
        self.bar
    }
}

fn main() {
    let aaaaa = 0;
    
    let mut f = Foo { bar: &aaaaa };
    
    let a = f.qux();
    let b = f.qux();
}