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throwup238 17h ago

> 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.

panstromek 15h ago

There's some movement on specialization as well: https://goals.rust-lang.org/2026/specialization.html

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.

afdbcreid 11h ago

More precisely: it wasn't known to be blocked on the new solver (unlike some other features), because nobody dared to touch it until recently... (more seriously, there wasn't enough investment).

KolmogorovComp 11h ago

I don't think rust is the future anymore, despite having contributed to its compiler few times and been quite involved for years. It has spread too much and that impact compiles time too much.

I think a newer language, having the boreness of go, the compile speed and maybe comp time of zig and safety of rust will emerge, maybe with lisp syntax.

pjmlp 3m ago

That already exists, OCaml.

The problem with Rust is lack of alternative implementations, like it happens in OCaml and Haskell, which allow for quick development loops, or going for lunch with an heavily optimised build.

raincole 7h ago

> I don't think rust is the future

Yeah because it's the present. Rust is everywhere now.

Buttons840 10h ago

What a weird take. At first I though you were going to predict a language with an even more featureful and strict type system.

We don't need the "boreness" and human usability of Go anymore. Fast compile times are still nice though.

Lisp syntax doesn't have much value in the age of AI I think. Lisp seems optimized to make it easy to parse, and also easy to hack on the interpreter. I don't think Lisp was ever meant to optimize human readability. The uniformity and minimalism of Lisp makes it easier to learn the syntax though. -- I don't know, maybe I underestimate the value and flexibility of Lisp syntax.

I think the most valuable features of programming languages now are human readability and type systems that give guarantees humans can rely on. Some of the most exciting code AI has written has been in Lean.

attila-lendvai 2h ago

the key impact of simple syntax is in metaprogramming.

secondary impact is structured editing, and maybe it's helping code reading by human brains.

vor_ 9h ago

Well, that implies there's some sort of threshold that it's still reaching for and hasn't yet achieved before it can be considered successful. But it's already everywhere now. Hell, not only is it in the Linux kernel, it's even in Windows (!).

Gigachad 8h ago

2026 has really been the year of Rust. The fact that it can run in the browser as well as natively has made it an electron killer.

pjmlp 2m ago

The problem with Electron is laziness of certain class of developers, no programming language will fix that.

chamomeal 10h ago

A lisp with the type safety of rust. Mmmmmm. Makes me do the homer drool

anthk 8h ago

Coalton?

xiaoyu2006 8h ago

typed racket!

xiaoyu2006 8h ago

https://xkcd.com/927/

outside1234 8h ago

Really? With AI you can have your cake and eat it too with Rust now.

yhjc2692 18h ago

Smaller target directory size would be such a lifesaver. Hoping the best for you, and Rust!

stymaar 16h ago

This!

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).

anonymous908213 15h ago

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".

simonask 15h ago

I have no idea about the code quality of Codex CLI, but it takes way way less time to build a full game engine (Bevy).

Stories like this make me think something is wrong with your setup. Do you have Windows Defender or similar enabled on the build directory?

shakna 13h ago

Bevy is intentionally sharded across many crates, is small, and has the dev working on optimised build times.

That isn't "Rust compiles are fast", it's another example of "Rust requires you architect your code a specific way".

afdbcreid 11h ago

> That isn't "Rust compiles are fast"

And neither the original example is "Rust compiles extremely slowly" (it does compile slowly), it's another example of "vibecoded software is of poor quality".

yosefk 12h ago

Fair enough but Rust also gives you a mix of safety and efficiency nothing else does

aliasxneo 13h ago

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.

afdbcreid 11h ago

It is slow. Nobody would deny that. It also requires work to avoid disastrous compile times, that's also true.

But 15 minutes? Even rustc doesn't take that long (on a powerful computer), and that's a very large program that is compiled at least twice (bootstrapping)! That's just poor engineering, not knowing how to write fast-to-compile Rust code.

okanat 13h ago

What kind of Rust projects? How many dependencies? Does it use macros? How about generics and traits?

Most of the Rust ecosystem makes unnecessarily heavy use of compile-time traits and monomorphized generics (aka Go generics or C++ templates). The language syntax encourages it as well. The thing is compile times will NEVER drop to level of Go unless the entire set of players (language, standard library, almost all library developers) actually prioritize dynamic dispatching instead of static dispatching / monomorphization. That's the tradeoff for the performance and RAM usage you gain. Template-heavy C++ also suffers from the same issues for the same reason.

Golang is fast to compile because its interface definitions are runtime/dynamically dispatched (aka `&dyn Trait` in Rust or virtual classes in C++) and it had no generics for a long time forcing types like slices, map and vectors to be magic types.

If you need fast compile times, you need to split your program into multiple binaries or write your own backend ecosystem that almost only uses dynamic dispatching. If your full Cargo dependency tree pulls 50+ crates, you'll not get fast compile times. You need to avoid derive-macros like plague. You need to use non-Cargo build systems or `build.rs` to generate Rust code instead of derive-macros.

Unlike Golang Rust also targets extremely memory constrained devices where monomorphization enables memory savings, extra optimizations and fewer CPU cycles / instructions (e.g. microcontrollers, UEFI/BIOS implementation). It is a system programming language first. With system programming languages you are responsible for these choices as the developer. Rust just happens to have a vivid scene of backend libraries since the language's safety enabled many non-system developers to write correct and performant programs quickly.

simonask 13h ago

Well, me too, and I can confidently tell you I’ve never seen build times in the 10+ minute range (on capable machines).

stymaar 12h ago

> it takes over 15 minutes to rebuild trivial changes on a top-shelf CPU

I have no idea how this could possibly be this bad given that I worked full time with Rust from 2015 to 2023 on a $600 Clevo laptop from 2012 and was used to incremental builds in the low double digit seconds for projects ranging between 100k and 600k loc. (From scratch release builds where excruciatingly slow, but these only happened once every rust updates).

afdbcreid 11h ago

You only clean the build directory once every Rust update? Unless you use nightly, I don't see how that's feasible. Having a 1TB (and pretty free) disk, I still need to clean regularly (not that commonly, but more than once a release).

xyzzy_plugh 14h ago

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.

iknowstuff 12h ago

Maybe the proposal you saw was breaking up into crates, which is Rust's compilation units and can be parallelized. They're not microservices, they're just libraries which still combine to produce a single binary.

yosefk 12h ago

Zig dumps core and Go is slower and needs more memory though, and this matters, too. (not that Rust build times are really a price to pay for avoiding these things, it's more a result of not making fast builds a goal from the start)

rapind 16h ago

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...).

estebank 15h ago

A partial solution that avoids you spending money is to stick `debuginfo = "line-tables-only"` in your `Cargo.toml`.

epage 14h ago

This will be the default for the `dev` profile in an upcoming release now that the `debug` profile has been split out.

colechristensen 15h ago

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.

rapind 12h ago

Yes it's a problem. Not dismissing it. Just a less expensive problem than CPU or RAM is all I'm saying. It's been a thorn for me too (being on a macbook myself, but now I have a dedicated build box).

RAM prices are insane right now...

d0mine 16h ago

~Zero build time Python vs 20 min for Rust web app

Filligree 15h ago

It's more than zero, but 15 seconds would be a great deal more realistic for an incremental build.

maccard 14h ago

Go is pretty close to 0 as well IME.

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!

d0mine 1h ago

Parsing JSON at tens of gigabytes per second… in Python

https://lemire.me/blog/2026/10/12/parsing-json-at-tens-of-gi...

pjmlp 1m ago

Nah, that is the usual mistake to call Python libraries to something that is actually implemented in a native compiled language.

stymaar 1h ago

Exception it's merely a python binding for Daniel Lemire's Simdjson which is written in C++ (which takes even more time to compile than Rust).

colechristensen 14h ago

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.

thomashabets2 18h ago

It would help, yes. Here's one of my projects, that uses different subdirectories in target/ based on compiler options pre-commit runs:

    $ du -hcs target/
    190G    target/

bitbasher 16h ago

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.

panstromek 15h ago

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?

rapind 16h ago

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.

It's been a journey...

simonask 16h ago

That sounds like something is very wrong with your setup.

MBCook 16h ago

Could you e plain the issue for a non-rustacean?

estebank 15h ago

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.

yhjc2692 14h ago

Woah, this is great to know. Thanks for explaining!

infogulch 13h ago

I'm curious about polymorphism. Should it be default on for debug builds just to save storage and compile time? How will rust decide whether to enable polymorphism? Will it be possible to provide source-level polymorphism hints to the compiler?

estebank 13h ago

The "hint" you could provide today for polymorphization is to write code like

    fn needs_string_like(x: Into<String>) {
        fn actual_logic(_: String) {}
        actual_logic(x.into())
    }

which is the explicit way of representing the same thing rustc would be doing automatically. The above will create an almost empty `needs_string_like` for each type that it is called with, but a single `actual_logic`. IIRC some optimization passess would completely remove specific instances of `needs_string_like` (like if you call `needs_string_like(String::new())`).

panstromek 12h ago

> polymorphism

I assume you ask about polymorphization, which is a term used to refer to a specific optimization mentioned in the blog post.

The base version which Rust wants the most makes sense to enable by default for all builds, because it's purely just removing duplicate work - this is for cases like Vec<u64> and Vec<i64>, where we currently emit code for each one separately, even though it's pretty much the same for both.

More general version will make sense for debug builds or in some special cases, like when optimizing for size. I believe people also want to experiment with it for some interop use cases (and for that, it'd be useful to have source level annotation). I think it's too early to tell how all of this is going to look like, though.

hmokiguess 18h ago

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.

anonymous908213 15h ago

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.

hmokiguess 14h ago

On this topic, how ironic that the Ruby dude who is getting infamous for doing this is preaching moving to Rust

panstromek 19h ago

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).

tialaramex 18h ago

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.

simplesocieties 9h ago

What are the problems in async the new trait solver will fix? Looking forward to building more on async Rust so I'm curious

yoshuaw 7h ago

Return Type Notation (RTN) I believe is the big one blocked by the new solver. This is the primitive that makes it possible to add bounds to futures returned by async functions. This should look something like: `where <T as Trait>::method(..): Send`.

This is one of two remaining features needed to make Async Functions in Traits (AFITs) practical. Dyn dispatch support being the other missing feature, though that isn't blocked by the new solver.

panstromek 2h ago

I was also thinking about Move and Forget traits, which impact cancellation safety. I think those are at least somewhat soft-blocked on the solver, but I'm not sure. Honestly, you're probably much better contact to talk about that, this is out of my wheelhouse.

KolmogorovComp 12h ago

I'm wondering about the future of clippy.

archermarks 11h ago

A bit out of the loop, what's going on with clippy?

KolmogorovComp 11h ago

is it going to be useful in a LLM-driven code-world.

vor_ 9h ago

Yes.

LoganDark 12h ago

Hexcat link is broken and leads to "https://https//hexcat.nl" instead of https://hexcat.nl

panstromek 2h ago

thanks, fixed ;)

shmerl 12h ago

Somewhat indirectly related, but is there any progress on implementing persistent caching in rust-analyzer? It would really benefit from faster startup times.

afdbcreid 11h ago

(r-a team member here) The progress is in Salsa (the incremental framework we use), not in r-a itself yet. And there is progress but it's not particularly fast, it's also not a priority for the r-a team (though if you want to contribute, you're welcome of course).

shmerl 10h ago

You mean progress to make the framework faster itself?

I was asking about something else, i.e. basically saving whatever possible from those expensive computations on disk, so next time it starts, it can spend significantly less time (assuming things didn't change too much). clangd has such feature and it's super helpful.

Or you mean Salsa already supports such persistent caching in some form?

afdbcreid 9h ago

I meant, the progress to make Salsa support persistent caching is not advancing particularly fast. It does exist, but is preliminary.

shmerl 8h ago

Ah, good to know. Thanks for clarifying!

UPDATE:

Found some pointers if anyone is interested:

* https://github.com/salsa-rs/salsa/issues/10

* https://hackmd.io/@ibraheemdev/S17Bxowwxg

vatsachak 16h ago

The best way to get a rust job is get a regular job and just write rust

cpursley 15h ago

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.

vatsachak 15h ago

Unless you work at a FAANG the team will ask you to make a tool and will probably be fine with a mainstream language.

2026 is an exciting year for the Rust compiler (and me) (yoyo-code.com)