#[derive(Debug)]
struct A<'a>
{
    pub b: &'a mut B,
}

impl<'a> A<'a>
{
    fn new(b: &'a mut B) -> A<'a>
    {
        A
        {
            b: b,
        }
    }

    fn foo(self) -> A<'a>
    {
        &self.b.bar();

        self
    }
}

#[derive(Debug)]
struct B
{
    b1: String,
}

impl B
{
    fn new() -> B
    {
        B
        {
            b1: String::from(""),
        }
    }

    fn bar(&mut self)
    {
        self.b1 = String::from("Foo Bar");
    }
}

fn main()
{
    let mut b = B::new();
    let a = A::new(&mut b); // Trying to avoid making a mutable.
    let a = a.foo();

    println!("{:?}", &a);
}