next-solver enable by default by lcnr · Pull Request #1896 · rust-lang/blog.rust-lang.org

lcnr · 2026-07-28T14:05:25Z

Should get merged together with rust-lang/rust#160619

cc @rust-lang/types @rust-lang/initiative-trait-system-refactor

Kobzol

🎉

Should the blog post mention a way to opt-out? Some people might want to use nightly, but not the next trait solver, if they run into any issues.

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pthariensflame

Some grammar/style/flow nits; no semantic changes. This was done entirely through our human brain and hands, without tool assistance of LLM-kind or any other.

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lcnr · 2026-08-12T12:08:04Z

Will actually publish this together with it actually being enabled by default, so reworded it slightly, performance and breakage is also in a far better spot than I originally thought, so I adapted the framing somewhat, still need to write the second half

pthariensflame

Another spelling/grammar/style pass like the previous.

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handled

Enable `-Znext-solver` on nightly by default Implementation of rust-lang/compiler-team#1014 cc rust-lang/blog.rust-lang.org#1896 #160895 This enables `-Znext-solver=globally` by default in nightly, but keeps `-Znext-solver=coherence` for tests

…nn,kobzol Enable `-Znext-solver` on nightly by default Implementation of rust-lang/compiler-team#1014 cc rust-lang/blog.rust-lang.org#1896 #160895 This enables `-Znext-solver=globally` by default in nightly, but keeps `-Znext-solver=coherence` for most tests.

theemathas · 2026-08-21T12:20:53Z

I assume this can be merged, now that rust-lang/rust#160619 has merged?

Kobzol · 2026-08-21T14:27:02Z

Just noting that the blog post says that it has already been enabled, but it will only be enabled from tomorrow's nightly. So if it is merged until then, it won't be accurate and people might get a bit confused if they read it in the next couple of hours.

Kivooeo · 2026-08-21T14:27:42Z

we can edit it a bit and say it will be enabled <date>

no rush though, im fine with wait a day before release a post

Kobzol · 2026-08-21T14:44:58Z

Sorry to be a buzzkill, but "tomorrow" is not a good date to have in a blog post xD (unless you would modify the blog post later) I'd suggest simply saying that it will be available on the nightly channel starting from Saturday 22nd August. It can still be confusing w.r.t. timezones and the fact that there are two dates involved with each nightly, but at least it won't be relative to whenever the reader reads the blog post 😆

lqd · 2026-08-21T14:45:09Z

let's ship it 🚀

lcnr · 2026-08-21T14:49:18Z

(unless you would modify the blog post later)

I would modify it once it is available on saturday :>

lcnr · 2026-08-21T14:50:44Z

⚠️ While the next-generation trait solver has been enabled on our main branch, this change will only be accessible on the nighly channel starting from Saturday 22nd August. You can already test it now by providing -Znext-solver=globally as a command-line argument to the most recent nightly version ⚠️

updated it to that with the expectation that we still remove it tmrw 😁

lqd

Years in the making 🚀

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lqd · 2026-08-21T14:57:02Z

Merging. If anyone wants more changes: open a PR :3

…nn,kobzol Enable `-Znext-solver` on nightly by default Implementation of rust-lang/compiler-team#1014 cc rust-lang/blog.rust-lang.org#1896 rust-lang/rust#160895 This enables `-Znext-solver=globally` by default in nightly, but keeps `-Znext-solver=coherence` for most tests.

…donszelmann,kobzol Enable `-Znext-solver` on nightly by default Implementation of rust-lang/compiler-team#1014 cc rust-lang/blog.rust-lang.org#1896 rust-lang#160895 This enables `-Znext-solver=globally` by default in nightly, but keeps `-Znext-solver=coherence` for most tests.

…nn,kobzol Enable `-Znext-solver` on nightly by default Implementation of rust-lang/compiler-team#1014 cc rust-lang/blog.rust-lang.org#1896 rust-lang/rust#160895 This enables `-Znext-solver=globally` by default in nightly, but keeps `-Znext-solver=coherence` for most tests.

theemathas reviewed Jul 28, 2026

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pthariensflame suggested changes Aug 5, 2026

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lcnr force-pushed the next-solver-enable-by-default branch from 0c11ed5 to 2a7074b Compare August 12, 2026 12:05

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jackh726 reviewed Aug 17, 2026

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jdonszelmann reviewed Aug 18, 2026

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lcnr mentioned this pull request Aug 18, 2026

Enable -Znext-solver on nightly by default rust-lang/rust#160619

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lcnr marked this pull request as ready for review August 18, 2026 13:16

lqd approved these changes Aug 18, 2026

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lcnr force-pushed the next-solver-enable-by-default branch from d2ec705 to e551c39 Compare August 18, 2026 14:10

lcnr mentioned this pull request Aug 20, 2026

Stabilize the next-generation trait solver rust-lang/goals#113

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lcnr force-pushed the next-solver-enable-by-default branch from f7ca3c1 to 38dce5b Compare August 21, 2026 14:24

lqd reviewed Aug 21, 2026

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lcnr force-pushed the next-solver-enable-by-default branch from bad00bd to 4782d80 Compare August 21, 2026 14:51

write next-solver blogpost

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lcnr force-pushed the next-solver-enable-by-default branch from 4782d80 to 26b2d92 Compare August 21, 2026 14:53

lqd approved these changes Aug 21, 2026

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lqd added this pull request to the merge queue Aug 21, 2026

Merged via the queue into rust-lang:main with commit 6f735c6 Aug 21, 2026
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lcnr deleted the next-solver-enable-by-default branch August 21, 2026 15:00

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