mir_let_chains_drop_order.rs

// run-pass
// needs-unwind
// ignore-wasm32-bare compiled with panic=abort by default

// See `mir_drop_order.rs` for more information

#![feature(let_chains)]
#![allow(irrefutable_let_patterns)]

use std::cell::RefCell;
use std::panic;

pub struct DropLogger<'a, T> {
    extra: T,
    id: usize,
    log: &'a panic::AssertUnwindSafe<RefCell<Vec<usize>>>
}

impl<'a, T> Drop for DropLogger<'a, T> {
    fn drop(&mut self) {
        self.log.0.borrow_mut().push(self.id);
    }
}

struct InjectedFailure;

#[allow(unreachable_code)]
fn main() {
    let log = panic::AssertUnwindSafe(RefCell::new(vec![]));
    let d = |id, extra| DropLogger { extra, id: id, log: &log };
    let get = || -> Vec<_> {
        let mut m = log.0.borrow_mut();
        let n = m.drain(..);
        n.collect()
    };

    {
        let _x = (
            d(
                0,
                d(
                    1,
                    if let Some(_) = d(2, Some(true)).extra && let DropLogger { .. } = d(3, None) {
                        None
                    } else {
                        Some(true)
                    }
                ).extra
            ),
            d(4, None),
            &d(5, None),
            d(6, None),
            if let DropLogger { .. } = d(7, None) && let DropLogger { .. } = d(8, None) {
                d(9, None)
            }
            else {
                // 10 is not constructed
                d(10, None)
            }
        );
        assert_eq!(get(), vec![3, 8, 7, 1, 2]);
    }
    assert_eq!(get(), vec![0, 4, 6, 9, 5]);

    let _ = std::panic::catch_unwind(|| {
        (
            d(
                11,
                d(
                    12,
                    if let Some(_) = d(13, Some(true)).extra
                        && let DropLogger { .. } = d(14, None)
                    {
                        None
                    } else {
                        Some(true)
                    }
                ).extra
            ),
            d(15, None),
            &d(16, None),
            d(17, None),
            if let DropLogger { .. } = d(18, None) && let DropLogger { .. } = d(19, None) {
                d(20, None)
            }
            else {
                // 10 is not constructed
                d(21, None)
            },
            panic::panic_any(InjectedFailure)
        );
    });
    assert_eq!(get(), vec![14, 19, 20, 17, 15, 11, 18, 16, 12, 13]);
}