os-rust/src/test/ui/did_you_mean/issue-42764.rs

// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

enum DoubleOption<T> {
    FirstSome(T),
    AlternativeSome(T),
    Nothing,
}

fn this_function_expects_a_double_option<T>(d: DoubleOption<T>) {}

fn main() {
    let n: usize = 42;
    this_function_expects_a_double_option(n);
}