[DO NOT MERGE] `-Znext-solver=globally` experiments by lcnr · Pull Request #133502 · rust-lang/rust

lcnr · 2024-11-26T15:26:47Z

A revival of #124812. See

Current status:

~~./x.py b --stage 2 passes 🎉~~

try builds succeed 🎉 🎉 🎉

first perf run 👻 second perf run 👻 third perf run 👻 fourth perf run 👻

crater

This does not detect hangs or memory issues. We are triaging the regressions in https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/crater.20triage.20.3A3/with/572783267 and welcome your help there.

date	#crates	#regressions
2025.04.11	100	2
2025.04.11	1000	27
2025.04.17	10000	456
2025.04.18	10000	437
2025.04.24	10000	164
2025.04.26	10000	108
2025.04.28	10000	91
2025.05.01	10000	145 woops
2025.05.03	624228¹	1585²
2025.05.05	8964³	931²
2025.05.06	4401³	726²
2025.05.07	2704³	668²
2025.05.09	2345³	664²
2025.09.20	701952¹	4739 + 7039 spurious
2025.10.02	11712³	2568 + 2014 spurious
2025.10.04	4582³	1173 + 1147 spurious²
2025.12.30	761102¹	1424 + 8938 spurious ²
2026.01.01	5745³	1371 + 3227 spurious ²
2026.01.06	4171³	1361 + 2623 spurious ²
2026.07.17	1014957¹	6502 + 11187 spurious ²
2026.07.20	17458³	991 + 3331 spurious ²
2026.07.23	4322³	959 + 1680 spurious ²
2026.07.31	1049848¹	1254 + 13493 spurious
2026.08.03	14035³	679 + 2245 spurious
2026.08.05	2915³	457 + 997 spurious

in-flight changes

none :3

r? @ghost

a complete crater run ↩ ↩² ↩³ ↩⁴ ↩⁵
with doubled recursion_limit when evaluating goals ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹²
only testing crates which may have regressed from the above run ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹²

compiler-errors · 2024-11-27T04:03:51Z

@bors try

[DO NOT MERGE] bootstrap with `-Znext-solver=globally` A revival of rust-lang#124812. Current status, we're failing in: - failing in `rustc_next_trait_solver` with 126 instances of the following error ``` error[E0311]: the parameter type `I` may not live long enough | help: consider adding an explicit lifetime bound --> compiler/rustc_next_trait_solver/src/solve/trait_goals.rs:624:53 | 624 ~ fn consider_structural_builtin_unsize_candidates<'a>( 625 ~ ecx: &mut EvalCtxt<'a, D>, 626 | goal: Goal<I, Self>, 627 ~ ) -> Vec<Candidate<I>> where I: 'a { ``` - `itertools` hangs, we're already encountered this hang in our previous attempt due to large type sizes. I believe that it's simply caused by a missing cache somewhere, potentially in `wf.rs`, but other visitors may also be responsible. See rust-itertools/itertools#945 for more details ### commits - rust-lang#133501 - rust-lang#133493 - 9456bfe and b21b116 reimplement candidate preference based on rust-lang#132325, not yet a separate PR - c3ef9cd is a rebased version of rust-lang#125334, unsure whether I actually want to land this PR for now r? `@ghost`

bors · 2024-11-27T04:05:03Z

⌛ Trying commit f631ca8 with merge ca04381...

compiler-errors · 2024-11-27T04:05:17Z

I also pushed:

I think this is sufficient to make the compiler build, or at least ./x.py build --stage=2 completes successfully on my local branch.

bors · 2024-11-27T06:15:40Z

💔 Test failed - checks-actions

bors · 2024-11-27T10:43:04Z

☔ The latest upstream changes (presumably #133527) made this pull request unmergeable. Please resolve the merge conflicts.

lqd · 2024-11-27T11:42:49Z

Next failure is on color-print-proc-macro-0.3.6 while building cargo.

pub fn repro() -> impl FnMut() {
    if true {
        || ()
    } else {
        || ()
    }
}

godbolt

compiler-errors · 2024-11-27T17:49:50Z

@bors try

[DO NOT MERGE] bootstrap with `-Znext-solver=globally` A revival of rust-lang#124812. Current status: `./x.py b --stage 2` passes 🎉 ### commits - rust-lang#133501 - rust-lang#133493 - 9456bfe and b21b116 reimplement candidate preference based on rust-lang#132325, not yet a separate PR - c3ef9cd is a rebased version of rust-lang#125334, unsure whether I actually want to land this PR for now - rust-lang#133517 * rust-lang#133518 * rust-lang#133519 * rust-lang#133520 * rust-lang#133521 * rust-lang#133524 r? `@ghost`

bors · 2024-11-27T17:51:02Z

⌛ Trying commit 6210ed3 with merge ac5ccad...

bors · 2024-11-27T20:03:42Z

💔 Test failed - checks-actions

compiler-errors · 2024-11-27T20:15:22Z

@bors try

[DO NOT MERGE] bootstrap with `-Znext-solver=globally` A revival of rust-lang#124812. Current status: `./x.py b --stage 2` passes 🎉 ### commits - rust-lang#133501 - rust-lang#133493 - 9456bfe and b21b116 reimplement candidate preference based on rust-lang#132325, not yet a separate PR - c3ef9cd is a rebased version of rust-lang#125334, unsure whether I actually want to land this PR for now - rust-lang#133517 * rust-lang#133518 * rust-lang#133519 * rust-lang#133520 * rust-lang#133521 * rust-lang#133524 r? `@ghost`

bors · 2024-11-27T20:16:33Z

⌛ Trying commit 8fa8f40 with merge 550ae0d...

lqd · 2024-11-27T20:26:10Z

I was reducing the new failure but you've already fixed it ^^

theemathas · 2026-07-27T06:53:10Z

The dist-x86_64-linux-quick failure is #159894

adwinwhite · 2026-07-27T08:39:09Z

Why wasn't this caught by the next-solver-polonius CI job? 🤔

theemathas · 2026-07-27T08:56:41Z

@adminwhite matthias says we somehow just don't have a test that would catch this, even in the old solver.

lqd · 2026-07-27T09:35:12Z

heapless is not in our Cargo.lock AFAICT, so only the dist job builds it, and the next-solver CI job can't catch the issue: it's a cargo dependency. The next-solver job only checks building std and bootstrapping, not building tools with the next solver enabled.

lcnr · 2026-07-27T11:16:49Z

@bors try

rust-bors · 2026-07-27T13:24:03Z

☀️ Try build successful (CI)
Build commit: 760e1de (760e1de835e253bf28bbcbfee38b5e8ed9ffe074)
Base parent: dfbea5b (dfbea5bc945a9d7ff017d3d4bfbd1af9295fe5b8)

lcnr · 2026-07-27T14:02:46Z

@craterbot check p=1

craterbot · 2026-07-27T14:03:04Z

👌 Experiment pr-133502-26 created and queued.
🤖 Automatically detected try build 760e1de
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-07-28T10:11:40Z

🚧 Experiment pr-133502-26 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-07-30T23:37:51Z

🎉 Experiment pr-133502-26 is completed!
📊 1254 regressed and 15 fixed (1049848 total)
📊 13493 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-133502-26/retry-regressed-list.txt ↩

adwinwhite · 2026-07-31T02:42:58Z

@craterbot check p=1 crates=https://crater-reports.s3.amazonaws.com/pr-133502-26/retry-regressed-list.txt

craterbot · 2026-07-31T02:43:07Z

👌 Experiment pr-133502-27 created and queued.
🤖 Automatically detected try build 760e1de
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-08-02T22:29:30Z

🚧 Experiment pr-133502-27 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-08-03T06:21:05Z

🎉 Experiment pr-133502-27 is completed!
📊 679 regressed and 0 fixed (14035 total)
📊 2245 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-133502-27/retry-regressed-list.txt ↩

lcnr · 2026-08-03T06:34:56Z

@bors try

rust-log-analyzer · 2026-08-03T07:08:58Z

The job aarch64-gnu-llvm-21-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

failures:

---- tests::test_unstable_options_tracking_hash stdout ----

thread 'tests::test_unstable_options_tracking_hash' (47444) panicked at compiler/rustc_interface/src/tests.rs:854:5:
assertion `left != right` failed
  left: NextSolverConfig { coherence: true, globally: true }
 right: NextSolverConfig { coherence: true, globally: true }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
---- tests::test_unstable_options_tracking_hash stdout end ----

failures:
    tests::test_unstable_options_tracking_hash

rust-bors · 2026-08-03T08:42:28Z

☀️ Try build successful (CI)
Build commit: 4d7f661 (4d7f6614d0baa7689bd05eba340114667db4d5b7)
Base parent: 65dd30f (65dd30fb9e882a7e8f0be10caca62936db2a98b8)

lcnr · 2026-08-04T07:57:57Z

@craterbot check p=1 crates=https://crater-reports.s3.amazonaws.com/pr-133502-27/retry-regressed-list.txt

craterbot · 2026-08-04T07:58:03Z

👌 Experiment pr-133502-28 created and queued.
🤖 Automatically detected try build 4d7f661
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-08-05T11:00:34Z

🚧 Experiment pr-133502-28 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-08-05T14:46:47Z

🎉 Experiment pr-133502-28 is completed!
📊 457 regressed and 0 fixed (2915 total)
📊 997 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-133502-28/retry-regressed-list.txt ↩

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Nov 26, 2024

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compiler-errors force-pushed the rust4 branch from c3ef9cd to f631ca8 Compare November 27, 2024 04:03

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bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 27, 2024

compiler-errors force-pushed the rust4 branch from f631ca8 to 6210ed3 Compare November 27, 2024 17:49

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compiler-errors force-pushed the rust4 branch from 6210ed3 to 8fa8f40 Compare November 27, 2024 20:15

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lcnr and others added 2 commits August 3, 2026 08:34

enable -Znext-solver by default

135b73c

rerun even if the goal has ty vars

f876bba

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This was referenced Aug 7, 2026

enable next solver by default in orphanck #160668

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Enable -Znext-solver on nightly by default #160619

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