| Objectively speaking, Rust does not "have a lot of great qualities that C++ lacks". Any new feature or improvement has its pluses, but also its minuses. * Rust has traits, but does not support OOP. Architectures where OOP is particularly effective are proving to be a significant challenge for Rust - GUIs are the obvious one, but also game development Rust projects have to invent new approaches. * Option/Result make the code flow obvious, but having to return them in nearly all function calls is tedious. Rust has had several attempts at alleviating this problem, but still hasn't matched the convenience of exceptions. * match is IMO syntactic sugar and its benefits for correctness are being oversold. The fact that one is basically obliged to use it leads to code that's sometimes too deep. Exceptions would cut through this error-handling noise, if they were available. * The build story is convenient, but this had the unintended effect of encouraging dependency explosion. Adding typical crates results in dozens of transitive dependencies being included in a project. The notable improvement that Rust brings to the table is machine-verified memory safety with C++-like performance, but that of course comes at the cost of having to adapt code to what the borrow checker understands. If one needs the feature, then the cost is worth paying, if not, Rust is more of a personal choice than an inevitable conclusion. And finally, perhaps Rust's biggest sin is that it's big, it's complex and there's no end in sight to the complexity spiral, just like for C++. I can only imagine the chagrin of the Rust community as they see themselves competing with Go for many projects where performance is not absolutely critical and often being second choice exactly because of this complexity. |
Among common uses for these more powerful features is to make misuse of the library into a compile-time error. Coding the library in Rust, if possible at all, would mean failing to prevent these usage errors.
The point here is that C++ puts more power in the hands of a library writer, and both the responsibility and capability to enforce safety in uses of the library. Rust jealously reserves maintaining safety to the compiler alone.