Code shared from the Rust Playground

playground.rs

struct Foo(u32);

struct Bar<'c>(&'c Foo);

impl<'h, 'c: 'h> Bar<'c> {
    fn new(foo: &'c mut Foo) -> Bar<'c> {
        Bar(foo)
    }

    fn baz(&'h self) -> Baz<'c> {
        Baz(&(self.0).0)
    }
}

struct Baz<'c>(&'c u32);

struct Quix<'c>(Bar<'c>, Option<Baz<'c>>);

impl Quix<'_> {
    fn setup(&mut self) {
        self.1 = Some(self.0.baz())
    }

    fn mu(&mut self) -> Result<(), Option<u32>> {
        Err(self.1.as_ref().map(|s| *s.0))
    }
}

fn main() {
    let c = || {
        let mut foo = Foo(42);
        let bar = Bar::new(&mut foo);

        let mut quix = Quix(bar, None);
        quix.setup();
        
        quix.mu()
    };
    
    println!("{:?}", c());
}