Veiled RefCell in Rust

hide.rs

use std::rc::Rc;
use std::cell::RefCell;
 
struct Wrapper {
    data_cell: RefCell<Data>,
}
struct Data {
    num: u8,
}
 
impl Wrapper {
    fn new() -> Rc<Wrapper> {
        Rc::new(Wrapper {
            data_cell: RefCell::new(Data { num: 0 }),
        })
    }
    
    fn inc(&self) {
        self.data_cell.borrow_mut().num += 1;
    }
    
    fn print(&self) {
        println!("{}", self.data_cell.borrow().num)
    }
}
 
fn main() {
    let test = Wrapper::new();
    
    test.print();
    test.inc();
    
    test.print();
    let closure = || test.inc();
    
    test.inc();
    test.print();
    
    closure();
    test.print();
}