struct Bar<'a, 'b>{
    a: &'a mut f64,
    b: &'b mut String,
}

impl<'a,'b> Bar<'a,'b>{
    pub fn new(a: &'a mut f64, b: &'b mut String) -> Self{
        Bar{
            a,
            b,
        }
    }
}

struct Foo<'ba, 'bb>{
    a: usize,
    b: f64,
    c: String,
    d: Bar<'ba, 'bb>
}

impl<'ba, 'bb> Foo<'ba, 'bb>{
    pub fn new() -> Foo<'ba, 'bb>{
        let a: usize = 0;
        let b: f64 = 0.0;
        let c: String = "Foobar".to_string();
        Foo{
            a,
            b,
            c,
            d: Bar::new(&mut b, &mut c)
        }
    }
}

fn main() {}