mrustc VS polonius

No, you don't. Existential proof: mrustc ignores lifetimes. Just flat out simply ignores. It changes some corner-cases related to HRBT, yet rustc compiled by mrustc works (that's BTW mrustc exist: to bootsrap the rustc compiler).

Incidentally C++ is the only way to bootstrap rust without rust today.

https://github.com/thepowersgang/mrustc

Well, there is mrustc[0], a Rust compiler that doesn't include a borrow-checker, so it's possible to compile (at least some versions of) Rust without a borrow checker, though it might not result in the most optimized code.

AFAIK there are some optimization like the infamous `noalias` optimization (which took several tries to get turned on[1]) that uses information established during borrow checking.

I'm also not sure what the relation with NLL (non-lexical lifetimes) is, where I would assume you would need at least a primitive borrow-checker to establish some information that the backend might be interested in. Then again, mrustc compiles Rust versions that have NLL features without a borrow-checker, so it's again probably more on the optimization side than being essential.

[0]: https://github.com/thepowersgang/mrustc

[1]: https://stackoverflow.com/a/57259339

> Maybe another memory safe language, but Rust has severe bootstrapping issues which is a hard sell for distros that care about source to binary transparency.

It is possible to bootstrap rustc from just GCC relatively easily, although it's a little bit time consuming.

You can use mrustc to bootstrap Rust 1.54: https://github.com/thepowersgang/mrustc

And from then you can go through each version all the way to the current 1.72. (Each new Rust version officially needs the previous one to compile.)

Have you tried this route : https://github.com/thepowersgang/mrustc ?

Mrustc supports Rust 1.54.0 today

There are three. The official one, mrustc (no borrow checker, but can essentially compile the official rustc) and GCC (can't really compile anything substantial yet). Only rustc is production-ready though.

That probably depends on what you mean by problematic. Having an ever increasing chain of dependencies isn’t the most desirable situation so there has been some work to trim the bootstrap chain. In 2018, when the blogpost I linked above was written, mrustc was used to bootstrap rust 1.19.0; now mrustc can bootstrap rust 1.54.0 so the chain to recent versions is much shorter than if all those intervening versions back through 1.19.0 needed to be built. https://github.com/thepowersgang/mrustc

Correctness prover which uses lifetimes (Polonius).

And, well, polonius (Rust borrow checker magic) I believe is built on datalog-ish concepts: https://github.com/rust-lang/polonius

There is also polonius (https://github.com/rust-lang/polonius) which should replace the borrow checker but does not receive a lot of development resources.

This is eventually going to be a feature-complete compiler, targeting a specific rustc version. I believe the plan is to use polonius [1], presumably as an "optional" feature so they can build a stage 1 without it, use that to build polonius, then build the final compiler with it included.

[1] https://github.com/rust-lang/polonius

E.g. there you may just stop using current borrow-checker and switch to Polonius.

The borrow checker is too dumb (https://github.com/rust-lang/polonius) fixes a lot of this.

It looks like an official borrow checker implementation called Polonius uses it as a dependency, so it makes sense: https://github.com/rust-lang/polonius/blob/981785c101b68ff54...

If you click around a little, you end up on a blog post with this tidbit:

> This project got put together rather suddenly, in response to some work the Rust folks are doing[1] on their new and improved borrow checker.

I don't think I could tell you more than "Frank wrote it to help rust folks who were previously doing work with differential-dataflow directly."

1. https://github.com/rust-lang/polonius/pull/36#issuecomment-3...

Good news is that there's also works going on to relax the restrictions, like polonius. But it seems that it still have a long way to go before it can land in stable Rust...

GCC-rs isn't intended for bootstrapping, it is intended to be an actual fully featured Rust compiler in the future, mrustc is a Rust compiler intended for bootstrapping though. GCC-rs is still very early targeting an older version of the reference compiler without things like a borrow checker, but that's not going to be the case forever. The GCC-rs folks have expressed interest in re-using the borrow checker library used by the reference compiler called polonius enabling them to relatively easily add borrow checking.