fn first_or_none(bytes: Span<u8>, index: usize) -> Maybe<u8> raises {
    check std.mem.get(bytes, index)
    return std.mem.get(bytes, index)
}

pub fn main(world: World) -> Void raises {
    let bytes: [2]u8 = [8, 9]
    let hit: Maybe<u8> = first_or_none(bytes, 1)
    let miss: Maybe<u8> = first_or_none(bytes, 9)
    if hit.has && hit.value == 9_u8 && !miss.has {
        check world.out.write("check maybe fallibility ok\n")
    }
}