>I've done significant C++ and Rust and Rust compiles WAY faster than C++ for day-to-day incremental compilation. C++ suffers from the header inclusion problem and modules may as well not exist because you can't practically use them.

It really depends on what you are compiling. I did lots of C/C++ that compiled 50k lines of code in 10 seconds FROM SCRATCH — I doubt you can do it in Rust. To be fair, headers in that project were somewhat optimized for compilation speed (not "hardcore", but "somewhat"). People forgot how fast C/C++ compilation can be without 10 Boost includes in each module.

>This is intentionally over complicated, there is no reason for the Box to be there.

Arc<RwLock<Option<T>>> — sounds good now? Don't get me wrong — C++ can be just as horrible, but Rust made it a rule, you can only write your program like this.

>What does this even mean?

I've already answered above, but I can repeat: there are runtime models that allow crash and recover, there are models that crash and limp. In Rust there is only one model of crash: you just crash.