> So I don't think we can separate the two in a meaningful way.

I think that in that case, you'd compare like with like, upgrading both.

I do agree that gcc and clang supporting older specs with a flag is a great feature, and is something that Rust cannot do right now.

But the results of the annual survey have come out: https://blog.rust-lang.org/2025/02/13/2024-State-Of-Rust-Sur...

And 90% of users use the current stable version for development. 7.8% use a specific stable released within the past year.

These numbers are only so high because it is such a small hassle to update even large Rust codebases between releases.

So yes, in theory, breakage can happen. But that's in theory. In practice, this isn't a thing that happens very much.