Re: Nothing new...
I don't know. How many Fortran programmers love Fortran? How many COBAL programmers love COBAL? The fact C is so very pervasive and yet its programmers still love it is very telling.
I've tried to read some of how Rust works. However certain things never make sense to me in many of these new languages.
.expect("Failed to read line");
Why would you chain together operations for input? Doesn't it make more sense to split complex problems into small independent pieces? If anything this looks a lot like an over-loaded function with optional parameters in C++.
So, OK. These new languages are there and OK and all that, but I don't think any of them are "better" than C. (Even C++ really isn't better.) In some ways they have advantages that C can / should never have. Garbage collection, memory safety, true exceptions. But none of that would ever have been possible in the 1970s, and such features have significant overhead.
C really is a great language. There are some others too. Swift and Rust are probably still too new to really tell how good they are.
As to OS calling conventions. If there's a better way to call functions across module and even program boundaries than C API, we should probably try to use it. I'm not sure how "Result" is going to cross language and environment boundaries though (or indeed even exceptions don't do that so well).