I work on small-ish embedded Linux systems and I've been looking for an alternative to C for a long time. Rust does not fit the bill, both because I don't enjoy the ergonomics of it (but I could get over that were it not for the other issues) and because the binaries are huge, so unless you go for a busybox-style multicall binary (and even then) you'll be wasting a lot of space. Both the standard size reduction techniques and splitting out things into shared objects (the ABI instability is not an issue on an embedded system which always gets compiled as a whole anyway) don't really move the needle compared to what you can achieve using plain C.
I've been meaning to give Swift a shot for applications like this. From what I've seen I had assumed that it would have less of a tendency to monomorphize everything (like Rust and C++ like to do when you use them idiomatically), leading to less binary size bloat.
You also mention binary size, but in relation to a library - is it that the absolute cost of including the library in the image is too high or is there a per-binary effect here as well?
Could you maybe share some of your experiences with Swift on embedded Linux in the context of that project? What is working well, what are the warts? What kind of distribution (like buildroot, Yocto, ...) are you using?
Sorry for the ton of questions, it's just something that has been on my bucket list for quite a while and it very exciting to hear that somebody is already doing this.