fn roundtrip_implicit_some_stack() {

    check_roundtrip(Option::<()>::None, "None");

    check_roundtrip(Some(()), "()");

    check_roundtrip(Some(Some(())), "()");

    check_roundtrip(Some(Some(Some(()))), "()");

    check_roundtrip(Some(Option::<()>::None), "Some(None)");

    check_roundtrip(Some(Some(Option::<()>::None)), "Some(Some(None))");

}

fn check_roundtrip<

    T: PartialEq + std::fmt::Debug + serde::Serialize + serde::de::DeserializeOwned,

>(

    val: T,

    check: &str,

) {

    let options =

        ron::Options::default().with_default_extension(ron::extensions::Extensions::IMPLICIT_SOME);

    let ron = options.to_string(&val).unwrap();

    assert_eq!(ron, check);

    let de: T = options.from_str(&ron).unwrap();

    assert_eq!(de, val);

}