What did you find complicated or terrifying there?
The fact that the code was complicated was sort of the point; the generic deriving code in the Rust compiler is in general a very tricky and confusing area and pretty complicated to deal with. In C++ I would have been very careful around code like this and not introduced new pointers. In Rust, I could do this without being afraid of memory issues.
You're not supposed to understand the actual code in the blog post; there's heaps of context and explanations of compiler internals I didn't want to do. I tried to make it clear what task I wanted to do, and how the compiler helped me carry it out; the code is just there to give a better idea of what was going on. If you read closely I do mention that a lot of things should be ignored, there.
The post also walks through the explanations of why the lifetimes work out that way, but that's more for the readers' edification -- I didn't need to actually figure anything out whilst working on it; the explanations are something I thought about later.
I'd argue that in order to properly evaluate your statements regarding C++ (and Rust, for that matter) it actually is important to understand the code and what you're trying to do. Given that there generally is more than one way to solve a problem it isn't unreasonable to think you found a solution that doesn't map (well) to C++ and from there generalize (perhaps incorrectly) that therefore it's impossible in C++ (with similar performance).
Well, in this case there aren't multiple solutions -- my solution was literally the problem statement. I wanted to make a particular array accessible later in the pipeline in a specific API. That was the problem statement (the reason behind this problem was that the plugin API needed to be able to expose this array). This itself was pretty simple. The array arose from a particularly entangled bit of code. Possible ways to persist it are with a regular or smart pointer/slice to the vector, in both Rust and C++.
The fact that the code was complicated was sort of the point; the generic deriving code in the Rust compiler is in general a very tricky and confusing area and pretty complicated to deal with. In C++ I would have been very careful around code like this and not introduced new pointers. In Rust, I could do this without being afraid of memory issues.
You're not supposed to understand the actual code in the blog post; there's heaps of context and explanations of compiler internals I didn't want to do. I tried to make it clear what task I wanted to do, and how the compiler helped me carry it out; the code is just there to give a better idea of what was going on. If you read closely I do mention that a lot of things should be ignored, there.
The post also walks through the explanations of why the lifetimes work out that way, but that's more for the readers' edification -- I didn't need to actually figure anything out whilst working on it; the explanations are something I thought about later.