fn main() {
    println!("Hello, world!");
    Foo::new(Baz("borrow")).run();
}

struct Baz<'a>(&'a str);

struct Foo<'a> {
    baz: Baz<'a>,
}

impl<'a> Foo<'a> {
    fn new(baz: Baz<'a>) -> Foo<'a> {
        Self {
            baz,
        }
    }
    fn run(&mut self) {
        Qux {
            mut_baz: &mut self.baz,
        };
    }
}

struct Qux<'a> {
    mut_baz: &'a mut Baz<'a>,
}