Re: Fifty years?
> gcc 10 can compile gcc 11, gcc 12, gcc 13.
Look at those version numbers and the maturity of the specific complier; now compare those to the maturity of Rust; now compare GCC (or other toolchains) when they were at the same level of maturity.
> It's quite normal to have a toolchain in use from several years ago that's still relevant and useful now
I never throw a toolchain away; my build system includes a copy of VC6 (the extant compiler when the build setup was started) and all of the compilers (mainly GCCs now) that have been used, right up to date. It really pisses me off when a compiler only comes as an installer that insists it is the only copy on the machine and even has to always be on PATH. Do not get me started on bleeping Arduino V2 that does not support a "portable" install. Anyway, back to your points.
> rust from a year ago can't compile Firefox... It's not sustainable to imagine finding a specific version of rust from a specific part of a specific year...
True. And for that, you need to point your anger at Firefox et al, who are knowingly using a toolchain that is still in the state of flux that every language starts with - and are doing so in production releases[[1], not as a parallel project preparing for the Rust developers to develop their toolchain.
The problem that exists today is people using for production releases a toolchain that is not yet ready for production use. Those same people would have been equally reckless around any other shiny, new and nowhere near standardised language. From that p.o.v. it is still not Rust's fault, qua Rust, yet another programming language; qua hype surrounding Rust and and the apparent urge to be visibly cutting edge, no matter the pitfalls, that is certainly at fault.[2]
But you started by talking about using Rust in 50 years time - a time frame that will either see Rust long settled into the maturity of GCC, with all the backwards compatibility flags, or will have seen Rust failed and excoriated decades earlier, as the issues you point out make even the Firefox team rebel against the Rust developers.[3]
I remind you of my opening line:
>> Much as I wish for a Rust that is less of a moving target,
That will come, or Rust will never make it to 50 years. Well, only as a relic that you can download from the Wayback Machine as a giggle.
[1] Worse, I have no doubt that they are proudly tracking point releases and compounding the problem.
[2] And jumping onto things and shoving them into production just because they are shiny is not restricted to Rust.
[3] Or everyone will have *finally* stopped pissing around with mediocre build systems and firing off builds with dozens of different compiler versions involved becomes no more difficult than typing "make" and leaving the machine to get on with it. Fat chance.[4]
[4] cue "but all the projects using Build System X already have that, to which the response will have to be "Yes, yes, but is everyone using X?". Anyway, that is a red herring (more of a bete noire, but I don't know to type accents on this device).