D is in the same space, but it started off having a GC and that kind of caused it more problems that it was perhaps worth being in an almost system space. Recent work with different allocator patterns and adding the -betterC compiler flag, I think, may help D in the long run. However, I wouldn't be surprised if D never gets much more popular that it already is.

The other major competitors to Rust is Zig and Jai. Of course Jai has the problem of being unreleased at the moment (and its fate is tightly bound to Jon Blow).

There are also a few other languages attempting to make inroads in the space. For example, Odin and Kit.

Here's my take on it though. C and C++ will always have some sort of systemic problem because they are able to do too much. In order to be a system language AND also do everything that people want a system language to do (games, embedded, high performance) you need (I assert) to have rough edges and dangerous pit falls.

Rust will eventually beat C/C++ on making web browsers and similar technologies because that's what it was built to do. However, Rust probably won't be able to beat C/C++ in game development and total OS development (although it can probably be partially used for both). Enter Zig and Jai.

D and Go both compete with C/C++ in a space that was temporarily taken over to Java/C#. But in the long run may end up being ceded to something that's less than a managed language but more than a system language.

Ultimately I predict we'll see C/C++ slowly give way to a family of system languages that all hold different niches before finally becoming a relegated to legacy only. This could still take a few decades to complete. And if you look at newer versions of C++ it's possible that C and C++ may even evolve to hold a different niche than the wide series of domains that they used to hold onto so tightly.

D isn't really competing with anything, it never took off. It already has a smaller market share than Rust while being twice as old (almost 20 years).

I'd call D a dead language. Can a dead language compete with a growing one?

Rust 1.0 was released in 2015, and before that you'd have breaking changes every month that effectively made it unusable for anything but toy projects. So it's not even 5 years old really.

Besides a big target for Rust is the C and C++ world. On Hacker News in my experience you have a majority of commenters coming from the web world where no news in one year effectively means that the project is dead.

For us in the low level world "stable for 4 years" means "maybe we can start considering using it in production" and the lack of big buzz every other month is more a pro than a con. I'll take boring and reliable over shiny and breaks-every-other-year.

I've just started adding a new feature on a C project started in 2009. If I used Rust I'd want to know that my dev environment will still be usable in 2019. I think the commitment to stability will pay off eventually.

Though I would argue they are different demographics somewhat. Mobile app and mac developers I would argue keep up with the times much more aggressively compared to c/c++ developers I know.