[verdagon]

I don't think it has to be this hard to have memory safety, data race safety, and performance. After building and doing PL design in this space for a decade, I don't believe the assumption that Rust's or C++'s difficulties are inherent.

I think C++ has its own legacy difficulties (which also make transitioning to memory safety tricky), and Rust's choice of borrow checking is only one (sometimes difficult) technique for getting these aspects. But there are almost a dozen other methods out there for getting memory safety besides RC, GC, or borrow checking.

I rather think that these other approaches aren't mature enough yet to enter the mainstream, and we haven't seen them yet.

[brigadier132]

How do you build a data race safe language without taking on the restriction of immutable data (which is imo, a much worse and bigger tradeoff than the borrow checker)?

I actually really like the borrow checker as a tradeoff, I think it makes code much easier to understand and it makes all aliasing bugs impossible. The removal of aliasing bugs is I think an undersold benefit of using rust.

[verdagon]

There are a lot of ways, but I think the most promising ones involve regions. We do this a lot manually in Rust, but a language could make this a first class concept. Some examples:

* Vale combines generational references and linear types with regions to eliminate overhead.

* Verona lets you divide memory into regions which can be backed by either arena allocation or GC. I think this is promising because for most GC regions you can completely avoid the collections.

* Cone lets you put borrow checking on top of any aliasing memory strategy, so could be something like the best of all these worlds.

* No language is doing this yet, but RC plus regions to eliminate the refcounts, then adding in value types for better cache usage, could be a real winner.

On phone so it's hard to get links, but you get the idea. The nice thing about regions is that they allow composing borrowing and shared mutability, something that the borrow checker struggles a bit with. Regions let us alias freely, and then freeze an entire area of memory all at once. Not that Rust isnt a good approach (it is!) but there are some easier techniques on the horizon IMO.

[dmytrish]

Please demonstrate a practical and memory safe systems programming language without borrowing.

I'd be delighted to see it, because right now I am not aware of any practical way to have memory safe regions without static tracking of borrowing from these regions. It's either that or runtime checking.

[verdagon]

This might be of interest: https://verdagon.dev/blog/first-regions-prototype

It uses region-based static analysis without borrow checking: it doesn't impose aliasability-xor-mutability per object, or even per-region.

Though, if you'd like to move the goalposts further to no form of borrowing at all, then I recommend looking at languages like Forty2 and Verona, they might be what you're looking for.

[dmytrish]

I have already spent more time than I wanted on reading through verbose but elusive articles about Vale, without any insight into how this actually happens.

I have already spent too much time trying to compile Vale compiler which is a weird mix of Scala and C++ with a small Vale driver. Once it is actually written in Vale without segfaults, I'll revisit the language again.

Thanks for the Verona recommendation.