It really depends what you count as "used in production." I don't count "one Rust library crate linked into your Zephyr/FreeRTOS/whatever project." I have yet to see any production bare-metal codebase written exclusively in Rust, at least at the kind of scale I deal with.
If you're in the middle of a supply chain like I am, often times your code is actually a reference design that gets forked by an OEM, tweaked to their liking, and integrated into a product. If the OEMs don't know Rust, they aren't gonna like it if I start handing them Rust reference code. Spoiler alert: they don't know Rust!
It goes the other way, too. A huge part of my job is working with drivers from Microchip, or Infineon, or Nordic, or whoever. They won't give me drivers in Rust. I could LLM my way out of that problem, but now I fully own my drivers with no first-party support, which is a huge step backwards from the current state of the art.
This isn't Rust's fault, of course, but it means that there's a ton of inertia, and that magnifies the effects of the issues that are Rust's fault.
If you're in the middle of a supply chain like I am, often times your code is actually a reference design that gets forked by an OEM, tweaked to their liking, and integrated into a product. If the OEMs don't know Rust, they aren't gonna like it if I start handing them Rust reference code. Spoiler alert: they don't know Rust!
It goes the other way, too. A huge part of my job is working with drivers from Microchip, or Infineon, or Nordic, or whoever. They won't give me drivers in Rust. I could LLM my way out of that problem, but now I fully own my drivers with no first-party support, which is a huge step backwards from the current state of the art.
This isn't Rust's fault, of course, but it means that there's a ton of inertia, and that magnifies the effects of the issues that are Rust's fault.