if e1 == BasicEnum::Option1 {
e1 = BasicEnum::Option2
}
In section "Parameters", you said "All three languages default to pass-by-value if not otherwise specified". For privitive types it's true, but it's not. Classes in Java have reference semantic (copy only address in method). Structs in Rust have move semantic witch is connacted with ownership concept (https://doc.rust-lang.org/stable/book/ownership.html).
In common, many basic things for Rust have very good descriptions in Rust Book (https://doc.rust-lang.org/stable/book/). Please, pay attension on it and be more careful.
I updated interfaces and enums. To your comment about move semantics for structs and such, I actually found the book lacking. I just did a quick Google search of the book for "move semantics" and couldn't find it anywhere. Where specifically does it talk about parameter passing?
Unfortunately, make_unique didn't make it into C++11, but is there for C++14