There are also these patterns one has to learn like applying references to numbers in some corner cases, e.g. func(&123), and the fact polominus is being developed shows there is still room for improvement on the borrow checker logic.

Neither of those were the case for me. In fact, I'd previously tried and failed to learn C (to a level where I could achieve something useful). I did learn at work, which gave me time as I was able to work on it full time, but I had no help available as nobody else at the company knew Rust at the time.

> Rust advocates tend to come back with an aggressive 'proof' that Rust is factually not hard to learn (with implications we can all guess at). No other programming community frequently does this in my experience (and I have brushed against many). That community attitude itself must have causes that are worth thinking about.

I somewhat agree this behaviour isn't great. I suspect the cause is a whole bunch of people saying that Rust is too hard, and that the industry therefore shouldn't bother with it.

Factors I'd guess at:

- Previous experience with a language that uses functional patterns is a huge plus. Even if that's very lightweight functional patterns like you might find in JavaScript or Kotlin (past exposure to something like Haskell or Scala would be even better). - Previous experience with C++ helps. Especially if you write "modern" C++ with smart pointers, etc as this is rather close to how Rust works. - C experience can be a positive or a negative. If you are the sort of C programmer who is hyper aware of object lifetimes and programs carefully and defensively it'll likely help. If you're the kind of C programmer who likes to play fast and loose with safety so long as it works in practice then it'll likely hinder as you'll expect to be able to do things that you can't. - Java/C# and other strongly OOP languages can make learning Rust harder. OOP code tends to be full of graphs of objects that all point to each other, and you just can't do this in Rust. So if that's how you're used to programming your going have to completely relearn how to structure code.

And I guess some of it's just going to be how comfortable people are with abstraction. Rust is definitely heavier on the mathier side of programming (with a sophisticated type system, etc). Personally I find that makes it easier not harder than languages like Go and C which are much simpler in this respect, as when reading code in those languages I often find it hard to pick out those forest from the trees. But from what I've seen, programmers are pretty split on their preferences on this issue, and I imagine for some people this would make it harder.