rust-orphan-rules VS polonius

Well, unless someone comes up with better, compatible rules, the orpan rules are gonna stick around.

Additionally there are other issues with rust currently. Compile time code (ala constexpr) is not up to par with C++20 (not really close). The const generic aren't as powerful as C++20 which added non primitive non type template parameters (though with you stuck with C++14, it actually is significantly better than what you have, again, if you're going to use C++, just use 20). Generics accepting closures is a bit more of an ordeal in rust, compared to C++. Also C++'s Duck Typed templates allow for some uncharacteristically strong typing compared to what is expressible in Rust generics currently. Now, duck typed templates do have major downsides, for example the entire feature of concepts is completely irrelevant in rust, but required for sane DTT type bounds, but they also have major upsides. Rust currently doesn't have "negative trait bounds", basically "This objected does not implement this trait, or std::enable_if> or the equivalent concepts implementation. Rust also doesn't have trait specializations, basically template specialization. Do note all features I've talked about to this point have nightly options, they just are at various stages of being stable/complete. Another issue is the orphan rule, though this is kind of a problem in C++ too in some respects, and that's unlikely to change drastically, since there are legitimate reasons for it's existence. For a lot of code none of these things are big deals, others they are, which is why you find inconsistent feed back on these issues.

Not that simple... hence why Orphan rule is still in-place. The struct wrapper was implemented in Rust as a temporary safe work-around. However, they are making progress on a solution: https://github.com/Ixrec/rust-orphan-rules/issues/1

That's still not an entirely complete explanation because there's more nuanced situations which aren't completely foreign but are foreign enough that if allowed, two crates could write the same impls. Some of the definitions are still unofficial as far as am I'm aware. For the best reference I’ve seen so far see this for more details.

In our crate the compiler doesn't know when calling MyTrait methods on MyStruct whether to use the implementation defined in crate 3 or crate 4! Rust has a set of orphan rules to prevent this situation from happening.

Sadly because of the rusts orphan rule you cannot implement a Trait on a Type where you do not own one or the other. So, apart from upstream contributions your only options are either a new Trait or a new Type.

If anyone is looking for additional background about orphan rules, check out https://github.com/Ixrec/rust-orphan-rules

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.