Code shared from the Rust Playground

playground.rs

#![feature(scoped_threads)]

use std::{thread, marker::PhantomData};

#[derive(Debug)]
struct SomeType(i32, PhantomData<*const()>); // make it !Send

// make it Sync. comment out to see compile error: cannot be shared between threads safely
unsafe impl Sync for SomeType {} 

fn main() {
    let mut T:  SomeType = SomeType(0, PhantomData);
    
    // &&mut T is Send, guranteed by cannot get `&mut T` from shared reference `&&T`
    let r = &&mut T; 

    // uncomment below line to see compile error: &mut T is !Send because T is !Send
    // let r = &mut T; 

    thread::scope(|s| {
        s.spawn(|| {
            let tmp = r;
            println!("{:?}", tmp);
            
        });
        s.spawn(|| {
            let tmp = r;
            println!("{:?}", tmp);
            
        });
    });

}