#![feature(explicit_tail_calls, unboxed_closures)]
#![expect(incomplete_features)]
#![allow(dead_code)]

#[derive(Copy, Clone)]
struct Thing { a: u64, b: u64, c: u64, d: u64 }

#[inline(never)]
fn seed_stack() {
    let mut values = (
        Thing { a: 100, b: 200, c: 300, d: 400 },
        Thing { a: 500, b: 600, c: 700, d: 800 },
    );
    std::hint::black_box(&mut values);
}

#[inline(never)]
extern "rust-call" fn callee((left, right): (Thing, Thing)) -> u64 {
    left.a.wrapping_add(left.b).wrapping_add(right.a).wrapping_add(right.b)
}

#[inline(never)]
extern "rust-call" fn caller((left, right): (Thing, Thing)) -> u64 {
    become callee((right, left));
}

fn main() {
    seed_stack();
    let left = Thing { a: 1, b: 2, c: 3, d: 4 };
    let right = Thing { a: 5, b: 6, c: 7, d: 8 };
    println!("got={}", caller((left, right)));
}