Read what the other commenters are pointing out. Maybe the situation is better in C++ now than it was before, but it doesn't mean you can't shoot yourself in the foot, specially for a beginner. Rust was built with safety in mind from the start, there are errors you can make in C++ that the Rust compiler simply won't let.

My advice is, if you're learning it for work, then go with C++. Even if it succeeds, it will take some years for Rust to be mainstream and as pointed out the library support is great.

If you're learning it for fun or for the sake of learning something new. Then Rust is a very nice and promising language bringing things from functional languages that C++ lacks and offering very interesting tooling around it.

Whatever you choose, after you feel confident with one go and learn the other as it will probably give a better perspective in the strengths and/or weaknesses of both.

I would just point out that the impetus for the Rust language was Mozilla looking for a better language to implement a browser in than C++. They obviously have a lot of experience writing C++ and how to do it as good as possible, but found it coming up short, especially as multi-core starts becoming the bottleneck.