rust/tests/ui/question_mark.rs

fn some_func(a: Option<u32>) -> Option<u32> {
	if a.is_none() {
		return None
	}

	a
}

pub enum SeemsOption<T> {
    Some(T),
    None
}

impl<T> SeemsOption<T> {
    pub fn is_none(&self) -> bool {
        match *self {
            SeemsOption::None => true,
            SeemsOption::Some(_) => false,
        }
    }
}

fn returns_something_similar_to_option(a: SeemsOption<u32>) -> SeemsOption<u32> {
    if a.is_none() {
        return SeemsOption::None;
    }

    a
}

pub struct SomeStruct {
	pub opt: Option<u32>,
}

impl SomeStruct {
	pub fn func(&self) -> Option<u32> {
		if (self.opt).is_none() {
			return None;
		}

		self.opt
	}
}

fn main() {
	some_func(Some(42));
	some_func(None);

	let some_struct = SomeStruct { opt: Some(54) };
	some_struct.func();

    let so = SeemsOption::Some(45);
    returns_something_similar_to_option(so);
}