use std::rc::{Rc, Weak};

struct Container {
    pub item: Rc<Item>,
    pub trait_ref: Weak<Box<Trait>>,
}

pub struct Item;
pub trait Trait {}
impl Trait for Item{}

fn main() {
    let item = Rc::new(Item);
    let trait_ref: Weak<Box<Trait>> = Rc::downgrade(&item);

    let _container = Container {
        item,
        trait_ref
    };
}