src/tools/miri/tests/run-pass/overloaded-calls-simple.rs

#![feature(lang_items, unboxed_closures, fn_traits)]

struct S3 {
    x: i32,
    y: i32,
}

impl FnOnce<(i32,i32)> for S3 {
    type Output = i32;
    extern "rust-call" fn call_once(self, (z,zz): (i32,i32)) -> i32 {
        self.x * self.y * z * zz
    }
}

fn main() {
    let s = S3 {
        x: 3,
        y: 3,
    };
    let ans = s(3, 1);
    assert_eq!(ans, 27);
}