Rust compiler support works differently

Posted Dec 16, 2025 14:34 UTC (Tue) by farnz (subscriber, #17727)
In reply to: Rust compiler support works differently by laarmen
Parent article: The state of the kernel Rust experiment

I've dug out some rather old code (written for 1.24, based on the rust-toolchain file), and it still builds quite happily with current nightly.

Do you have examples of crates that were written for older versions of rustc, didn't use unstable features, but that don't work with current rustc? I'm curious to see what's actually broken - I know about the changes to std::env::set_var, for example, and I'm wondering what else has broken over the last decade or so.

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Rust compiler support works differently

Posted Dec 16, 2025 14:48 UTC (Tue) by laarmen (subscriber, #63948) [Link]

Yes, most old code will compile without issues. AFAICT, the Rust compatibility story is one of the best out there. The only specific example that comes to mind right now is Rust 1.80 vs `time`, but that one was special in that it was actually detected and disregarded. However, I do remember reading several times in Rust changelogs things like "We detected XX crates that failed to compile with this change and worked with their authors to get a new, fixed version out".