SIMD at least has hope of running on bare metal. I suppose the ideal is to have it adjustable: compiled to non-SIMD, using typical SIMD hardware, using implicit threads (and thus needing OS support), or using SIMD hardware with threads.
I fear the high-level web developers are in the driver's seat, which may doom rust as a systems language. I'm hesitating on rust because I would miss bitfields and various unsafe performance features. I like the opt-out safety of the "unsafe" keyword, but I want more things that I can opt out of. I want goto, computed goto, no-default switches, something like Microsoft's __assume keyword, and all the other low-level stuff you'd want for making boot loaders and high-performance kernels.
You're probably thinking of Tokio, the library for async network IO, which obviously depends on an OS. The async/await language feature compiles down to basically a state machine and has minimal runtime requirements. I'm looking forward to using it on bare-metal microcontrollers.
The largest, most well known executor is Tokio, which is built on top of OS primitives. If you're writing your own OS, you'd use those primitives.
> I fear the high-level web developers are in the driver's seat
First, I pretty fundamentally reject this as an idea, but since you don't, please do a Google Scholar search for many of the core team members. They're very much not web developers.
I mean, I like it too, but the point upthread is that you can't just suck in every nice-looking idea or you'll end up like C++.
They didn't, not individually. They were popular and uncontroversial (rather less controversial than promise apis, even). And yet...
The point is that Rust seems to be charging blindly down the same road, not that any one feature is going to blow it all up. Frankly IMHO Rust is already harder to learn for a median programmer than C++ is, even if it makes more aesthetic sense to an expert.
I'm not saying Rust is bad. I'm saying it's... becoming senselessly complicated. And that in 20 years when 60% of its amazing new features turn out to be just fashion (because they happens to everything), Rust will be "ugly" then in basically the same way that C++ is now, and we'll all be chasing some other new hotness.
2) I seriously doubt you or I have good stats on how many people who are writing production ready C++ would consider Rust hard.
To Edinburgh we go, then.