Using RefCell for multiple mutable references

main.rs

use std::cell::RefCell;

fn main() {
    let a = A {
        msg: String::from("Hi!"),
    };
    let x = RefCell::new(a);
    let b = B { b: &x };
    let c = C { c: &x };
    b.b.borrow_mut().say_hi();
    c.c.borrow_mut().msg = String::from("Bye!");
    b.b.borrow_mut().say_hi();
}

pub struct A {
    msg: String,
}

impl A {
    pub fn say_hi(&mut self) {
        println!("{}", self.msg);
    }
}

struct B<'a> {
    b: &'a RefCell<A>,
}

struct C<'a> {
    c: &'a RefCell<A>,
}