Rust code shared from the playground

playground.rs

use std::ptr;
use std::marker::PhantomData;

struct Sealed<T> {
    brand: *const *const i32,
    value: T,
}

struct SealerUnsealerPair<T> {
    brand: *const i32,
    phantom: PhantomData<T>,
}


impl<T> SealerUnsealerPair<T> {
    pub fn seal(&self, value: T) -> Sealed<T> {
        Sealed {
            brand: &self.brand,
            value: value,
        }
    }
    pub fn unseal(&self, it: Sealed<T>) -> Option<T> {
        if ptr::eq(&self.brand, it.brand) {
            Some(it.value)
        } else {
            None
        }
    }
    pub fn new() -> SealerUnsealerPair<T> {
        SealerUnsealerPair {
            brand: ptr::null(),
            phantom: PhantomData,
        }
    }
}

fn main() {
    let sealer1 = SealerUnsealerPair::new();
    let sealer2 = SealerUnsealerPair::new();
    let sealed1 = sealer1.seal("foo");
    let sealed2 = sealer2.seal("bar");
    let sealed1_2 = sealer1.seal("abc");
    let sealed2_2 = sealer2.seal("xyz");
    assert!(sealer1.unseal(sealed1).is_some());
    assert!(sealer1.unseal(sealed2).is_none());
    assert!(sealer2.unseal(sealed2_2).is_some());
    assert!(sealer2.unseal(sealed1_2).is_none());
    ()
}