propose 2025h2 Goals #3849

nikomatsakis · 2025-08-15T21:56:34Z

Per https://blog.rust-lang.org/inside-rust/2025/06/23/project-goals-2025h2-call-for-submissions/, here is the proposed slate of 2025H2 goals.

Rendered

nikomatsakis · 2025-08-15T22:08:51Z

As in prior rounds, we'll follow an unusual FCP process here. Leads must check their boxes, others are encouraged but not required to do so.

bootstrap

cargo

compiler

crates-io

infra

lang

lang-docs

leadership-council

libs

libs-api

opsem

project-exploit-mitigations

@rcvalle (required, lead)
1c3t3a (optional)
cuviper (optional)

rustdoc

spec

testing-devex

types

wg-compiler-performance

wg-mir-opt

text/0000-Project-Goals-2025h2.md

Co-authored-by: Eric Holk <[email protected]>

eholk · 2025-08-15T22:52:36Z

I love seeing how many goals are like "this builds on work from previous goals," or "this goal resolves blockers discovered in previous goals." It shows the goal program has been going long enough that it's starting to build some momentum throughout the project.

ehuss · 2025-08-16T01:00:03Z

Similar to last time, I would recommend changing leadership-council to not be optional.

Kobzol

Great job! Looks really good.

Kobzol · 2025-08-16T07:10:07Z

text/0000-Project-Goals-2025h2.md

+| [Production-ready cranelift backend](https://rust-lang.github.io/rust-project-goals/2025h2/production-ready-cranelift.html) | [Folkert de Vries][] | [compiler], [wg-compiler-performance]                        |
+
+
+The "Flexible, fast(er) Rust builds" initiative focuses on improving Rust's build system to better serve both specialized use cases and everyday development workflows:


What does "Rust's build system" mean? It sounds like the goal is to improve bootstrap 😅 Maybe something like "focuses on improving compilation of Rust programs ..."?

Cargo is rust's canonical build system. Absolutely no doubt in my mind it means "improving cargo"

Huh, that didn't even cross my mind. Maybe if it was "Rust build system", but "Rust's build system" sounds to me like it builds Rust, not builds Rust programs. Anyway, apart from build-std, these improvements are not Cargo specific.

Let me rephrase for greater clarity!

weihanglo · 2025-08-16T09:58:25Z

text/0000-Project-Goals-2025h2.md

+[Tomas Sedovic]: https://github.com/tomassedovic
+[TC]: https://github.com/traviscross
+[Weihang Lo]: https://github.com/weihanglo
+[@whlo]: https://github.com/whlo


Some of my handle are wrong.

@whlo should be either Weihang Lo or @weihanglo.

rust-lang/rust-project-goals#375

D'oh! Thanks.

nikomatsakis · 2025-08-16T11:49:12Z

Similar to last time, I would recommend changing leadership-council to not be optional.

So, that falls out from not having a lead. I can definitely tweak the script but I'm curious to hear your reasoning on that. Is it because you think the LC should generally be aligned on the "goal slate overall" or is it related to the Vision Doc goal, which is the only one that cited the LC.

ehuss · 2025-08-16T13:24:48Z

LC should generally be aligned on the "goal slate overall" or is it related to the Vision Doc goal, which is the only one that cited the LC.

Just the Vision Doc goal. It's just a formality, since I believe we've already says "yes" to it. I would just like to be careful with teams that don't have a lead to avoid things slipping through without consensus. Last time there were goals we weren't even aware of, so it was a bit different.

nikomatsakis · 2025-08-16T20:42:14Z

@ehuss ok, I'll make the change

text/0000-Project-Goals-2025h2.md

Mark-Simulacrum · 2025-08-17T20:38:02Z

text/0000-Project-Goals-2025h2.md

+| [Production-ready cranelift backend](https://rust-lang.github.io/rust-project-goals/2025h2/production-ready-cranelift.html) | \*1 |
+
+
+\*1: track and show `rustc_codegen_cranelift` performance ([from here](https://rust-lang.github.io/rust-project-goals/2025h2/production-ready-cranelift.html))


Can we clarify whether this means wg-compiler-performance owning the implementation and deployment work? I think the ongoing project from Arm on adding aarch64 (https://rust-lang.github.io/rust-project-goals/2025h1/perf-improvements.html) is probably a pre-requisite or at least strongly related to this.

I don't think the team as-is can commit to this happening without outside contributions (including potentially a funding ask from the Foundation, depending on how long the additional tests take -- presumably just limited to the dev profile?).

If we can just switch to cranelift only that's much easier to pull off though.

The linked rustc-perf project is 100% a pre-requisite for this. That being said, I expect it to be prepared for deployment in 2-3 months, so it should coincide with the Cranelift project fine, I think.

Once the new rustc-perf scheme lands, we will be able to do Cranelift benchmarks on demand on arbitrary PRs (it will backfill the missing results for the parent commit, which doesn't happen now).

If we want to automatically run Clif on each perf. run by default, that's also doable, we'd "just" need to buy a second perf. machine on Hetzner.

text/0000-Project-Goals-2025h2.md

1c3t3a · 2025-08-18T10:49:06Z

text/0000-Project-Goals-2025h2.md

+| [Prototype a new set of Cargo "plumbing" commands](https://rust-lang.github.io/rust-project-goals/2025h2/cargo-plumbing.html)                                      | ![Help Wanted][] | [cargo]                                                                               |
+| [Stabilize cargo-script](https://rust-lang.github.io/rust-project-goals/2025h2/cargo-script.html)                                                                  | [Ed Page][]           | [cargo] ([Ed Page][]), [compiler], [lang] ([Josh Triplett][]), [lang-docs] ([Josh Triplett][])     |
+| [Continue resolving `cargo-semver-checks` blockers for merging into cargo](https://rust-lang.github.io/rust-project-goals/2025h2/cargo-semver-checks.html)         | [Predrag Gruevski][]      | [cargo] ([Ed Page][]), [rustdoc] ([Alona Enraght-Moony][])                                          |
+| [Emit Retags in Codegen](https://rust-lang.github.io/rust-project-goals/2025h2/codegen_retags.html)                                                                | [Ian McCormack][]        | [compiler] ([Ralf Jeffery][]), [opsem] ([Ralf Jeffery][])                                                 |


I can only guess that this means @RalfJung instead of Ralf Jeffery (ralfj@ on GH)? cc: @icmccorm.

Yes—that was a typo, thanks!

Whoops, let me see if I can fix that :)

I opened #376 with a fix for this — sorry for the delay!

text/0000-Project-Goals-2025h2.md

petrochenkov · 2025-08-18T16:02:07Z

text/0000-Project-Goals-2025h2.md

+
+[Bastian Kersting]: https://github.com/1c3t3a
+[Amanieu d'Antras]: https://github.com/Amanieu
+[@BN]: https://github.com/BN


This is supposed to be https://github.com/b-naber.

petrochenkov · 2025-08-18T16:02:56Z

text/0000-Project-Goals-2025h2.md

+[Guillaume Gomez]: https://github.com/GuillaumeGomez
+[James]: https://github.com/Jamesbarford
+[Pete LeVasseur]: https://github.com/PLeVasseur
+[Ralf Jeffery]: https://github.com/RalfJ


This is supposed to be https://github.com/RalfJung.

petrochenkov · 2025-08-18T16:03:30Z

text/0000-Project-Goals-2025h2.md

+[Aapo Alasuutari]: https://github.com/aapoalas
+[Alona Enraght-Moony]: https://github.com/adotinthevoid
+[Jon Bauman]: https://github.com/baumanj
+[@boxy]: https://github.com/boxy


-> https://github.com/boxyuwu

petrochenkov · 2025-08-18T16:04:35Z

text/0000-Project-Goals-2025h2.md

+[Folkert de Vries]: https://github.com/folkertdev
+[Frank King]: https://github.com/frank-king
+[Ian McCormack]: https://github.com/icmccorm
+[Tugce Ciftci]: https://github.com/imperio


-> https://github.com/GuillaumeGomez

petrochenkov · 2025-08-18T16:05:15Z

text/0000-Project-Goals-2025h2.md

+[Ian McCormack]: https://github.com/icmccorm
+[Tugce Ciftci]: https://github.com/imperio
+[Jack Huey]: https://github.com/jackh726
+[@jackwrenn]: https://github.com/jackwrenn


-> https://github.com/jswrenn

Thank you :)

RalfJung · 2025-08-19T12:21:29Z

text/0000-Project-Goals-2025h2.md

+| [In-place initialization](https://rust-lang.github.io/rust-project-goals/2025h2/in-place-initialization.html)                                                      | [Alice Ryhl][]        | [lang] ([Taylor Cramer][])                                                                    |
+| [C++/Rust Interop Problem Space Mapping](https://rust-lang.github.io/rust-project-goals/2025h2/interop-problem-map.html)                                           | [Jon Bauman][]         | [compiler] ([Oliver Scherer][]), [lang] ([Tyler Mandry][]), [libs] ([David Tolnay][]), [opsem]                  |
+| [Finish the libtest json output experiment](https://rust-lang.github.io/rust-project-goals/2025h2/libtest-json.html)                                               | [Ed Page][]           | [cargo] ([Ed Page][]), [libs-api], [testing-devex]                                         |
+| [MIR move elimination](https://rust-lang.github.io/rust-project-goals/2025h2/mir-move-elimination.html)                                                            | [Amanieu d'Antras][]         | [compiler], [lang] ([Amanieu d'Antras][]), [opsem], [wg-mir-opt]                                  |


Amanieu is not in t-lang though, so... what does this row mean?

He's an advisor.

Co-authored-by: Josh Triplett <[email protected]>

Co-authored-by: lcnr <[email protected]>

davidtwco · 2025-08-21T09:37:51Z

text/0000-Project-Goals-2025h2.md

+* [Polonius](https://rust-lang.github.io/rust-project-goals/2025h2/./polonius.html) will enable new borrowing patterns, and in particular [unblock "lending iterators"](https://github.com/rust-lang/rust/issues/92985). Over the last few goal periods we have identified an "alpha" vesion of polonius that addresses the most important cases while being relatively simple and optimizable. Our goal for 2025H2 is to implement this algorithm in a form that is ready for stabilization in 2026.
+* The [next gen trait solver](https://rust-lang.github.io/rust-project-goals/2025h2/./next-solver.html) is a refactored trait solver that unblocks better support for numerous language features (implied bounds, negative impls, the list goes on) in addition to closing a number of existing bugs and unsoundnesses. Over the last few goal periods, the trait solver went from early prototype to being production use in coherence. The goal for 2025H2 is to prepare it for stabilization.
+* The work on [evolving trait hierarchies](https://rust-lang.github.io/rust-project-goals/2025h2/./evolving-traits.html) will make it possible to refactor some parts of an existing trait out into a new supertrait so they can be used on their own. This unblocks a number of features where the existing trait is insufficiently general, in particular stabilizing support for custom receiver types, a prior project goal that wound up blocking on this refactoring. This will also make it safer to provide stable traits in the standard library, while preserving the ability to evolve them in the future.
+* The work to [expand Rust's `Sized` hierarchy](https://rust-lang.github.io/rust-project-goals/2025h2/./scalable-vectors.html) will permit us to express types that are neither `Sized` nor `?Sized`, such as extern types (which have no size) or ARM's Scalable Vector Extensions (which have a size that is known at runtime, but not compilation time). This goal builds on [RFC #3729](https://github.com/rust-lang/rfcs/pull/3729) and [RFC #3838](https://github.com/rust-lang/rfcs/pull/3838), authored in previous project goal periods.


Suggested change

* The work to [expand Rust's `Sized` hierarchy](https://rust-lang.github.io/rust-project-goals/2025h2/./scalable-vectors.html) will permit us to express types that are neither `Sized` nor `?Sized`, such as extern types (which have no size) or ARM's Scalable Vector Extensions (which have a size that is known at runtime, but not compilation time). This goal builds on [RFC #3729](https://github.com/rust-lang/rfcs/pull/3729) and [RFC #3838](https://github.com/rust-lang/rfcs/pull/3838), authored in previous project goal periods.

* The work to [expand Rust's `Sized` hierarchy](https://rust-lang.github.io/rust-project-goals/2025h2/./scalable-vectors.html) will permit us to express types that are neither `Sized` nor `?Sized`, such as extern types (which have no size) or Arm's Scalable Vector Extension (which have a size that is known at runtime, but not compilation time). This goal builds on [RFC #3729](https://github.com/rust-lang/rfcs/pull/3729) and [RFC #3838](https://github.com/rust-lang/rfcs/pull/3838), authored in previous project goal periods.

tmandry · 2025-08-30T06:05:37Z

text/0000-Project-Goals-2025h2.md

+| [In-place initialization](https://rust-lang.github.io/rust-project-goals/2025h2/in-place-initialization.html)                                    |               | Two design meetings |          |     |
+| [MIR move elimination](https://rust-lang.github.io/rust-project-goals/2025h2/mir-move-elimination.html)                                          |               |                     | ✅        |     |
+| [Nightly support for Autoreborrow traits](https://rust-lang.github.io/rust-project-goals/2025h2/autoreborrow-traits.html)                        |               |                     |          |     |
+| ↳ Design autoreborrow internals                                                          | \*2           |                     | ✅        |     |


I think this one should focus on the experiment, and perhaps design meeting to surface open questions and get feedback. This is a design that I think would benefit a lot from an experiment to prove it out ahead of accepting an RFC, so it's unlikely we can do so this year. cc @aapoalas

Put in suggested changes to the three lines to go along these lines more.

tmandry · 2025-08-30T06:12:29Z

text/0000-Project-Goals-2025h2.md

+| [C++/Rust Interop Problem Space Mapping](https://rust-lang.github.io/rust-project-goals/2025h2/interop-problem-map.html)                         |               |                     |          |     |
+| [Const Generics](https://rust-lang.github.io/rust-project-goals/2025h2/const-generics.html)                                                      |               | \*3                 |          |     |
+| [Continue Experimentation with Pin Ergonomics](https://rust-lang.github.io/rust-project-goals/2025h2/pin-ergonomics.html)                        |               | ✅                   |          |     |
+| [Design a language feature to solve Field Projections](https://rust-lang.github.io/rust-project-goals/2025h2/field-projections.html)             | \*5           | \*4                 | ✅        |     |


Getting to an RFC decision this year seems like a stretch, unless we try the "RFC the problem statement and solution criteria" approach. The design has had many iterations which puts it farther along, but there are still some major open questions, and the experiment is just getting started. cc @BennoLossin

Yeah I originally put it there since I wasn't 100% aware of the lang experiment process and I thought we'd need an RFC to have an experiment. As Tyler already said, there are some major open questions that we have to answer before we can have a new RFC. It might be possible that we make lots of progress and are able to have satisfying answers by the end of the year, but we also might not make progress on some of them. So I would lower the expectations of producing a finished RFC, let alone deciding to merge one.

aapoalas · 2025-08-30T07:16:51Z

text/0000-Project-Goals-2025h2.md

+| ↳ Finish and stabilize `arbitrary_self_types` and `derive_coerce_pointee`                |               |                     |          | ✅   |
+| [In-place initialization](https://rust-lang.github.io/rust-project-goals/2025h2/in-place-initialization.html)                                    |               | Two design meetings |          |     |
+| [MIR move elimination](https://rust-lang.github.io/rust-project-goals/2025h2/mir-move-elimination.html)                                          |               |                     | ✅        |     |
+| [Nightly support for Autoreborrow traits](https://rust-lang.github.io/rust-project-goals/2025h2/autoreborrow-traits.html)                        |               |                     |          |     |


Maybe we can simplify the name here; the code has drifted from "Autoreborrow" to using just "Reborrow", and "Nightly support for" is kind of superfluous.

Suggested change

| [Nightly support for Autoreborrow traits](https://rust-lang.github.io/rust-project-goals/2025h2/autoreborrow-traits.html) | | | | |

| [Reborrow traits](https://rust-lang.github.io/rust-project-goals/2025h2/autoreborrow-traits.html) | | | | |

or perhaps "Reborrow traits experiment".

aapoalas · 2025-08-30T07:19:18Z

text/0000-Project-Goals-2025h2.md

+| [In-place initialization](https://rust-lang.github.io/rust-project-goals/2025h2/in-place-initialization.html)                                    |               | Two design meetings |          |     |
+| [MIR move elimination](https://rust-lang.github.io/rust-project-goals/2025h2/mir-move-elimination.html)                                          |               |                     | ✅        |     |
+| [Nightly support for Autoreborrow traits](https://rust-lang.github.io/rust-project-goals/2025h2/autoreborrow-traits.html)                        |               |                     |          |     |
+| ↳ Design autoreborrow internals                                                          | \*2           |                     | ✅        |     |


Suggested change

| ↳ Design autoreborrow internals | \*2 | | ✅ | |

| ↳ Experiment with Reborrow trait design | \*2 | | ✅ | |

aapoalas · 2025-08-30T07:21:37Z

text/0000-Project-Goals-2025h2.md

+| [MIR move elimination](https://rust-lang.github.io/rust-project-goals/2025h2/mir-move-elimination.html)                                          |               |                     | ✅        |     |
+| [Nightly support for Autoreborrow traits](https://rust-lang.github.io/rust-project-goals/2025h2/autoreborrow-traits.html)                        |               |                     |          |     |
+| ↳ Design autoreborrow internals                                                          | \*2           |                     | ✅        |     |
+| ↳ Implement non-recursive autoreborrowing                                                |               | ✅                   |          |     |


propose 2025h2 Goals

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Co-authored-by: Eric Holk <[email protected]>

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Tracking issue joshtriplett/project-goal-reference-expansion#11

Open

		\| [Production-ready cranelift backend](https://rust-lang.github.io/rust-project-goals/2025h2/production-ready-cranelift.html) \| [Folkert de Vries][] \| [compiler], [wg-compiler-performance] \|


		The "Flexible, fast(er) Rust builds" initiative focuses on improving Rust's build system to better serve both specialized use cases and everyday development workflows:

		\| [Production-ready cranelift backend](https://rust-lang.github.io/rust-project-goals/2025h2/production-ready-cranelift.html) \| \*1 \|


		\*1: track and show `rustc_codegen_cranelift` performance ([from here](https://rust-lang.github.io/rust-project-goals/2025h2/production-ready-cranelift.html))

	\| [Nightly support for Autoreborrow traits](https://rust-lang.github.io/rust-project-goals/2025h2/autoreborrow-traits.html) \| \| \| \| \|
	\| [Reborrow traits](https://rust-lang.github.io/rust-project-goals/2025h2/autoreborrow-traits.html) \| \| \| \| \|

	\| ↳ Design autoreborrow internals \| \*2 \| \| ✅ \| \|
	\| ↳ Experiment with Reborrow trait design \| \*2 \| \| ✅ \| \|

	\| ↳ Implement non-recursive autoreborrowing \| \| ✅ \| \| \|
	\| ↳ Seek feedback for an RFC based on experiment \| \| ✅ \| \| \|

propose 2025h2 Goals #3849

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propose 2025h2 Goals #3849

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bootstrap

cargo

compiler

crates-io

infra

lang

lang-docs

leadership-council

libs

libs-api

opsem

project-exploit-mitigations

rustdoc

spec

testing-devex

types

wg-compiler-performance

wg-mir-opt

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nikomatsakis commented Aug 15, 2025 •

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