tests/ui/foreign/extern-rust-ffi-warning-64593.rs

// https://github.com/rust-lang/rust/issues/64593
//@ check-pass
#![deny(improper_ctypes)]

pub struct Error(std::num::NonZero<u32>);

extern "Rust" {
    fn foo(dest: &mut [u8]) -> Result<(), Error>;
}

fn main() {
    let _ = unsafe { foo(&mut []) };
}