alt Hacker NewsApple claims Swift can be used for systems programming, and is (partly) eating its own dogfood by using it in FoundationDB (https://news.ycombinator.com/item?id=38444876) and by providing examples of embedded projects (https://www.swift.org/get-started/embedded/)
I think they are right in that claim, but in making it so, at least some of the code loses some of the readability of Swift. For truly low-level code, you’ll want to give up on classes, may not want to have copy-on-write collections, and may need to add quite a few some annotations.
Swift is very slow relative to rust or c though. You can also cause seg faults in swift with a few lines. I Don't find any of these languages particularly difficult to read, so I'm not sure why this is listed as a discriminator between them.