[aussiesnack]

But I've never heard a C++ programmer deny that it's a large and difficult language.

I personally never really had a problem with ownership model - probably because what I was doing fell into the simple buckets. Rust's difficulty goes well beyond ownership. I just thought the Rust user forum thread I quoted was a gently funny example of the Rust community's denial: "Rust's not hard, but to get a decent mental model of the borrow checker you need to read the standard library, or if not here's 10000 words on how I think of it". I'm not presenting it as "proof" that Rust is hard - the fact that I couldn't do anything practical with it after more troublesome attempts than with any other language is plenty enough for me to know that. Neither do I think difficulty is 'bad'. Denying it can be though.

[jcranmer]

That's someone who's defining "mental model" as effectively "build a formal model of how this things worth without actually using formalism for everything." Of course everyone in that thread is coming up with very complicated stuff, because OP explicitly asked them to do so.

Yes, Rust's borrower checker is more complicated than equivalent features in other languages. If you read the writings of the Rust language developers, you'll notice that they basically admit that it's where Rust sinks its entire complexity budget, so there's no room to spend it anywhere else. But I don't think it's too complex--it's not complex enough for average developers to not be productive. I would contrast this with C++'s template metaprogramming, which I believe to be too complex for average developers to be productive (e.g., trying to write templates that switch based on the types of the parameters, especially before if constexpr).