> It's easy to understate how big of a deal this is for the compiler. This work resolves a major piece of technical debt that a lot of compiler developers dreamed about for years.
No kidding. I’ve been waiting for the solver at least half that decade now. Hopefully it and Polonius unblock specialization which has been in purgatory for years.
It's not directly blocked on the solver, but getting the type system into a better shape definitely helps reasoning about the soundness issues involved.
There's a recurring meme here and in other social media about rust being slow to compile, but anyone who's worked with Rust know that target dirs are a much more annoying papercut in practice than the relative speed of the compiler (which isn't appreciably worse than any other toolchain out there for the most common workflows).
A papercut is an unbelievable way to describe this. I tried forking Codex CLI and, for a terminal UI that manages chats and HTTP requests, it takes over 15 minutes to rebuild trivial changes on a top-shelf CPU with all incremental/caching optimizations, and tens of GBs in build caches. Neither of those is acceptable. Full stop. I am aware part of the problem is that Codex CLI is a vibe-coded monstrosity (surprise, software is not solved), but I've not had this problem with vibe-coded monstrosities in eg. Go. Hold your language to better standards. That doesn't mean abandon Rust; that means strive to make the Rust toolchain better than the Go toolchain rather than shrugging your shoulders and saying "lol this is fine no way anybody could do anything about this".
I've seen three outages at various orgs that were prolonged due to compile times. In these cases it was a root contributor to missing RTO. The compile times are a liability.
One proposal I came across actually suggested breaking up a perfectly fine monolith into a dozen microservices to reduce compile times (at the cost of cumulative CI costs going up).
When the alternative is massively rearchitecting your systems, Zig and Go begin to look really nice by comparison.
Weird take. I've worked in large Rust projects for half a decade (in one case, a full blockchain written in Rust). It's slow, full stop. I was under constant pressure to keep CI times down and was resorting to some of the craziest optimizations just to save a few minutes. Meanwhile, all of the platform code I was writing in Go almost never had a CI time above a few minutes.
Doesn't mean one is better than the other, but to find it odd someone had an experience with slow Rust compiliations and then blame it on their setup is a bit odd.
Both (and memory) are a problem. Build sizes is definitely more easily solved just by throwing more disk at it though (unless you are using a hard constrained mac...).
A good 4TB SSD was $1000 the last time I checked. The "throw more resources at it" attitude makes all but very top tier equipment kinda useless for many cases.
I had to abandon several projects until I bought a significantly beefier computer because of disk space, which is ridiculous. A lot of it was rust target directories taking up tens of gigabytes.
Funnily enough, last week I was working on parsing some json. I wrote a little script in python, tested it and then ran it over the main dataset. It took so long that I rewrote it in C# before the python script had finished!
I have a whole section in my global AGENTS.md about how python sucks to influence agents to not use it for anything performance sensitive.
My favorite improvement example was something a bit of a slog was taking 20 minutes in python, I told the agent to rewrite it in rust and the result was 300,000 times faster... 20 minutes to ones of milliseconds. Obviously not just a python problem but better solutions just seem to fall out of Rust and Python is just slow.
I can deal with large builds, what I cant deal with is time. My rust web application takes 20 minutes to build in release mode on a high end developer machine. I can’t build it in ci/cd.
Yeah, there are some things I've done to mitigate this, especially for the dev loop. Moving templates out of rust (losing some safety). Splitting the application into vertical slices. Only generating code that's changed. Turning features into crates.
20 minut definitely sounds suspicious. For comparison, Rust compiler takes ~10 minutes to build in release mode (in the simple config without all the fancy PGO stuff we run on CI).
Do you have some more info about the codebase, is it public?
The Rust toolchain by default produces a lot of debug information for each crate being compiled and the language relies heavily on monomorphization (instantiating a different function/type for each combination of generics) which translates to generally having duplicated functionality where the only difference in the object code is the different types. These two things combined, along with large dependency trees and that "features" for conditional compilation cause the same crate to be considered different across different workspaces (meaning the rlibs that were created for one can't be reused for another), means that the target directory for Rust projects can quickly grow. That, + clippy not having stabilized an already implemented process to automatically delete files from the target directory when they are unlikely to be needed again (which can't be 100% accurate, it uses heuristics because a developer could always potentially need an exact rlib from 6 months ago, it is just unlikely) means that you can expect that under the default configuration your target directory ends up being huge after a short period of time.
A lot of those things are in different stages of being fixed. I would personally want the default for generated debug information to be changed. cargo gc will help with running out of disk space. Better cross-project reuse of existing rlibs could be accomplished with some better tracking of optional features that can be unified (think having `serde` with feature `derive` enabled in one project, and having it without it in another: features are supposed to be purely additive, so you could reuse the earlier rlib on the later, but in practice people (ab?)use features in non-additive ways so it isn't straighforward to do something like that by default). Tools like hakari lets you create workspace-unified Cargo.toml to emulate this behavior.
I don't understandy why, but all submissions of this post so far had incorrect title. When I posted the correct one, it still got reassigned the wrong title and I had to edit it (and it didn't allow me to do that yesterday, only today).
Hacker News has some automatic fixes for title text. Some - perhaps all - of them can walk into false positives where a change that's usually desirable instead ruins the title either because it's a joke and the change spoils the joke or just because English is complicated.
Pretty wild to see how different people’s experiences can be within the same industry but under different applications and circumstances, here is someone joyful about the future of a language whereas not long ago we had a Ruby gem maintainer in deep dissatisfaction and frustration with the future of it.
Not implying to compare Rust and Ruby, just mainly observing how these two things came out near each other in the present day.
Leadership matters. I don't suppose the Rust leaders have been telling their community to write more open-source code for free with the express purpose of replacing those people with LLMs trained on their work.
I did this once but with Elixir, and it worked - because I shipped ahead of schedule (way ahead of the other teams portions). Performance and quality met the standards. Sometimes it's better to ask for forgiveness than permission if that means not having to fool with Java.
It is not. Tell me one good reason to deal with the horrible language called rust now that we have mechanisms capable of doing the exact same stuff in a vastly less obnoxious manner....(I am talking about running LLMs over your C code once in a while).
I don't like rust because
1. Verbose Syntax made worse by having to include type system info...
2. Dumb Borrow checker
3. Automagic stuff...
That may be true 1 time. Or 100 times. But unless you can show that it's true every single time, all you're doing is intentionally adding bugs into the world. And if you really can do it successfully 100% of the time, then you're smart enough to know that whoever maintains the code after you probably isn't able to do it and you should use something better anyway.
No kidding. I’ve been waiting for the solver at least half that decade now. Hopefully it and Polonius unblock specialization which has been in purgatory for years.
It's not directly blocked on the solver, but getting the type system into a better shape definitely helps reasoning about the soundness issues involved.
There's a recurring meme here and in other social media about rust being slow to compile, but anyone who's worked with Rust know that target dirs are a much more annoying papercut in practice than the relative speed of the compiler (which isn't appreciably worse than any other toolchain out there for the most common workflows).
One proposal I came across actually suggested breaking up a perfectly fine monolith into a dozen microservices to reduce compile times (at the cost of cumulative CI costs going up).
When the alternative is massively rearchitecting your systems, Zig and Go begin to look really nice by comparison.
Stories like this make me think something is wrong with your setup. Do you have Windows Defender or similar enabled on the build directory?
Doesn't mean one is better than the other, but to find it odd someone had an experience with slow Rust compiliations and then blame it on their setup is a bit odd.
I had to abandon several projects until I bought a significantly beefier computer because of disk space, which is ridiculous. A lot of it was rust target directories taking up tens of gigabytes.
Funnily enough, last week I was working on parsing some json. I wrote a little script in python, tested it and then ran it over the main dataset. It took so long that I rewrote it in C# before the python script had finished!
My favorite improvement example was something a bit of a slog was taking 20 minutes in python, I told the agent to rewrite it in rust and the result was 300,000 times faster... 20 minutes to ones of milliseconds. Obviously not just a python problem but better solutions just seem to fall out of Rust and Python is just slow.
It's been a journey...
Do you have some more info about the codebase, is it public?
A lot of those things are in different stages of being fixed. I would personally want the default for generated debug information to be changed. cargo gc will help with running out of disk space. Better cross-project reuse of existing rlibs could be accomplished with some better tracking of optional features that can be unified (think having `serde` with feature `derive` enabled in one project, and having it without it in another: features are supposed to be purely additive, so you could reuse the earlier rlib on the later, but in practice people (ab?)use features in non-additive ways so it isn't straighforward to do something like that by default). Tools like hakari lets you create workspace-unified Cargo.toml to emulate this behavior.
Not implying to compare Rust and Ruby, just mainly observing how these two things came out near each other in the present day.
I don't like rust because
1. Verbose Syntax made worse by having to include type system info... 2. Dumb Borrow checker 3. Automagic stuff...