C++ still isn't cutting it
To summarize:1) Rust's standard idioms (in this case, Results and Iterators) encourage less bug-prone or ambiguous APIs (standard and otherwise)2) Rust's ecosystem makes it easy to find and integrate solutions not offered by the standard API3) And then finally, Rust's borrow checker prevented a threading issueOthers are rightly pointing out that only #3 is fundamentally unique to Rust. All of these other things could be done for C++. But, importantly, they haven't.This raises an interesting dimension to the comparison which is that many of Rust's advantages don't really come down to its unique traits (heh) but to the simple fact that it's "C++ without baggage". It had a fresh start when it came to establishing standard idioms for everyone to use, providing cross-platform tooling for everyone to use, providing centralized package management for everyone to use, etc. If you introduced to C++ a Result type, or a package manager (I assume people have done this already), most C++ developers wouldn't end up using them. Most libraries wouldn't be using the same vocabulary. It would be arduous to even move the standard library over, because it would be a breaking change. Much of the tooling out there would probably never get specialized support.I don't think these network effects and cultural forces get talked about enough. Sure, this stuff is "just a library", and C++ has libraries. But the culture and the baggage and the stakeholders around a language have a huge impact on what ends up being practical to do with it, independent from what's technically possible.