On Mon, Jul 30, 2018 at 5:02 PM gibix <gi...@riseup.net> wrote: > This will allows projects like rustfmt, clippy, bindgen that need runtime > linking with the proper rust version to work correctly. Beyond this while > rust is getting older as project we will see more projects that will > require a specific rust version for compilation. >
As I mentioned in the PR already, I'm not a fan of this change. (Context: I have been writing Rust code for 2 years, I'm on the Rust team, and I've done most of the maintenance on the dev-lang/rust ebuilds for the past year or so.) As far as I know, the Rust ecosystem is largely bimodal: stuff is either compatible with stable and later, or it works only on nightly. It seems very rare that code is actually tied to a particular Rust release and does not compile against latest Rust stable. (Upstream actually promises they won't break code except in case they need to fix a soundness issue in the compiler.) So instead of building this whole target infrastructure (which is definitely needed for something like Python or Ruby), we should be able to just work with stable and nightly slots, and ebuilds can depend on those. Upstream is also very clearly packaging their core tooling as a single package made up of a number of components, and these are distributed and compiled together in common usage on other platforms (with the rustup tooling). That also means they are tightly coupled -- for example, rustfmt can change formats over time, and CI that checks formatting will need to align with whatever the current stable Rust version of rustfmt is. Installing the latest (nightly or beta) version of rustfmt while you have a stable Rust toolchain installed is thus not a good idea. As another example, cargo is now tagged as 0.28, but when passing --version it will report as 1.27.0 -- actually the Rust toolchain version. For these reasons, I think it would be better to align our Rust ebuilds with upstream and work with single ebuilds (dev-lang/rust and dev-lang/rust-bin) that install all the tools belonging to a particular version of the Rust toolchain. What tools are installed can be customized with USE flags, and the default install can be minimal (just rustc and cargo, which you need to build packages anyway). Regards, Dirkjan
