I wrote a fair amount of Rust code in 2012, none of it on a real project like servo. All of it just code to try to understand what the language was trying to make easy. None of that code compiles any more. (Or enough of it fails that I stopped looking at it.)
It's not so much a "critique" as it is a confirmation that when the crustaceans tell you the language definition isn't finished yet, believe them. I like the feel of Rust much more than C/C++, but I have C code I wrote in 1982 that still compiles and does what you think it should do. C++ code from 1990 still seems to compile. I have Rust code from 2014 that won't even compile.
Rust is a cool language and I hope it eventually settles down enough to be considered for "real" projects. I've done a little bit of Ada in the last year and I really, really want something better. But... reverse in-compatibility is a deal-breaker for some corners of the commercial world.
And yes, I know that (like Python) you can build an environment that lets you continue to compile old code with old compilers and some old code with new compilers. But the projects I'm talking about have life-times measured in decades. Will rustc in 2055 be able to compile a program written today? It doesn't seem to be on the top of minds of most of the Rust community.
I'm not saying Rust is ugly. In fact, I really like some aspects of the language. And post 1.0 is MUCH better than pre 1.0. But if we could go for a few years without breaking changes that would be nice.
But a few years later, in 2015, Rust 1.0 shipped. So the stability really firms up from there.
I happen to have in front of me the first commit of the first modestly sized piece of software I wrote in Rust in April 2021. Which compiles today just fine and works exactly as it did when it was written, on this brand new Rust toolchain.