Rust: UnwindSafe

unwind_safe.rs

//! https://doc.rust-lang.org/std/panic/fn.catch_unwind.html

use std::panic::UnwindSafe;
use rand::random;

struct Boxed<'a, T> {
    inner: &'a mut [T],
}

impl<'a, T> UnwindSafe for Boxed<'a, T> {}

fn bad<'a, T>(t: Boxed<'a, T>) -> &'a mut T {
    if random::<f32>() <= 1.0 {
        panic!("I failed on purpose.");
    } else {
        t.inner.get_mut(0).unwrap()
    }
}

fn main() {
    let boxed = Boxed {
        inner: &mut [1, 2, 3],
    };
    match std::panic::catch_unwind(|| bad(boxed)) {
        Ok(r) => println!("Ok = {r}"),
        Err(err) => println!("Err = {err:?}"),
    }
}