llvm-project VS chalk

I forgot to say that I use this llvm build. Just download the release and point the clangd server to it.

Xtensa support (esp32). Will be interesting how this will be for Rust and Zig support for esp32

https://github.com/llvm/llvm-project/tree/main/llvm/lib/Targ...

https://www.phoronix.com/news/LLVM-Xtensa-Backend

https://github.com/espressif/llvm-project/issues/4#issuecomm...

https://github.com/ziglang/zig/issues/5467#issuecomment-1465...

Hopefully, in the future the installation will be simpler, as we are trying to upstream our LLVM changes (first 10 patches are already accepted!), and once we manage to upstream LLVM changes we will proceed with upstreaming our Rust fork changes.

The main discussion can be led back to this GitHub issue and this comment; fortunately, we don't need to build espressif's llvm fork anymore as they supply the clangd (this is the language server we need) and you can find the zip here. I'll briefly list down the steps required to set up vim with clangd to take advantage of clangd's features (auto-completion, linting, code refactoring ...)

In my case, it's pretty annoying that the Xtensa platform doesn't have official LLVM support. It's in progress but going very slowly.

The link to the espressive issue trackers: https://github.com/espressif/llvm-project/issues/4

Xtensa. They've got a fork of LLVM that supports it that they're working toward getting upstreamed. The community has a fork of rustc that uses it (and a quickstart crate) while we wait for it to get upstreamed.

https://github.com/espressif/llvm-project/issues/4 is a good example why updating llvm isn't easy and takes a lot of time.

Just to clarify - Gambit, Chicken, and Carp all compile to portable C.

I hadn't realized LLVM mainline doesn't support Xtensa. I'm surprised.

D does support Xtensa via LDC (https://forum.dlang.org/thread/[email protected]...). It looks like GDC also nearly supports it, requiring only a minor patch at present.

A functioning LLVM backend does exist (https://github.com/espressif/llvm-project/issues/4) and might be making very slow progress towards being merged. A quick search shows that it works for Rust. I suspect (but don't know) that it might work for Terra as well.

There's also the LLVM C backend (https://github.com/JuliaComputingOSS/llvm-cbe) but I've no idea how efficient such an approach is when applied to real world embedded tasks.

The Rust compiler uses a Prolog-like query language internally for type checking generic requirements and traits: https://github.com/rust-lang/chalk

rust-analyzer already uses chalk (https://github.com/rust-lang/chalk) which should replace the current trait resolver.

Well it's quite easy to come to that conclusion: The code compiles with rustc, which is currently the reference implementation. If rust-analyzer does not match rustc's behavior it's an issue in their implementation. That written it's not that easy to fix as it's related to how rust-analyzer resolves types/traits. rust-analyzer uses chalk for this, which is known to be incomplete/diverging from the RFC'ed behavior. Now one could argue that we can simplify diesel to the point where it works will with rust-analyzer/chalk, but that would result in basically removing core diesel features that exist way longer than rust-analyzer.

> Not all of those things work well in the real world. E.g. logic programming (prolog) is cool but ultimately never really caught on.

It does have its niches though. For example, there is a trait solver for Rust called Chalk that uses a Prolog-inspired language because trait bounds basically define a logic:

https://github.com/rust-lang/chalk

Maybe something in the prolog/datalog direction could be useful? Notably Rust has Chalk to help with trait resolution ("Chalk is a library that implements the Rust trait system, based on Prolog-ish logic rules.")

There has been work to implement part of the Rust typing logic in the Chalk Engine which uses a prolog-ish syntax to describe its rules.

That's something Chalk is trying to tackle.

We probably will see all of them at some point -- polonius is a current effort to make the borrow checker accept more valid programs, in a way that also simplifies the logic and is probably a bit faster than the current NLL system, chalk is an attempt to do a similar thing for the trait system, and cranelift is a project that seeks to replace the LLVM codegen backend. But obviously, these are very large and complex projects that are gonna take some time.

Do Rust developers realize that? Oh, yes, absolutely, that's why we have this:

For me an attempt to write where HashMap: FromIterator and then use new and insert was totally bizzare because currently rustc is pretty primitive and doesn't do super-complex machinery needed to do what you want. Chalk may fix that one day, but it's nowhere near to being ready for inclusion into rustc thus I wouldn't even attempt to do what you tried to do… but that's not something you are supposed to know before reading this book!