Rollup of 4 pull requests #152373

Zalathar · 2026-02-09T03:32:02Z

Successful merges:

Implement MVP for opaque generic const arguments #150823 (Implement MVP for opaque generic const arguments)
Implement stdio FD constants #152071 (Implement stdio FD constants)
Port rustc_strict_coherence to the new attribute parser #152171 (Port rustc_strict_coherence to the new attribute parser)
Port rustc_insignificant_dtor #152291 (Port rustc_insignificant_dtor)

Failed merges:

Port rustc_reservation_impl to the new attribute parser #152180 (Port rustc_reservation_impl to the new attribute parser)

This is meant to be the interim successor to generic const expressions. Essentially, const item RHS's will be allowed to do arbitrary const operations using generics. The limitation is that these const items will be treated opaquely, like ADTs in nominal typing, such that uses of them will only be equal if the same const item is referenced. In other words, two const items with the exact same RHS will not be considered equal. I also added some logic to check feature gates that depend on others being enabled (like oGCA depending on mGCA). = Coherence = During coherence, OGCA consts should be normalized ambiguously because they are opaque but eventually resolved to a real value. We don't want two OGCAs that have the same value to be treated as distinct for coherence purposes. (Just like opaque types.) This actually doesn't work yet because there are pre-existing fundamental issues with equate relations involving consts that need to be normalized. The problem is that we normalize only one layer of the const item and don't actually process the resulting anon const. Normally the created inference variable should be handled, which in this case would cause us to hit the anon const, but that's not happening. Specifically, `visit_const` on `Generalizer` should be updated to be similar to `visit_ty`.

@BoxyUwU

Implement MVP for opaque generic const arguments This is meant to be the interim successor to generic const expressions. Essentially, const item RHS's will be allowed to do arbitrary const operations using generics. The limitation is that these const items will be treated opaquely, like ADTs in nominal typing, such that uses of them will only be equal if the same const item is referenced. In other words, two const items with the exact same RHS will not be considered equal. I also added some logic to check feature gates that depend on others being enabled (like oGCA depending on mGCA). ### Coherence During coherence, OGCA consts should be normalized ambiguously because they are opaque but eventually resolved to a real value. We don't want two OGCAs that have the same value to be treated as distinct for coherence purposes. (Just like opaque types.) This actually doesn't work yet because there are pre-existing fundamental issues with equate relations involving consts that need to be normalized. The problem is that we normalize only one layer of the const item and don't actually process the resulting anon const. Normally the created inference variable should be handled, which in this case would cause us to hit the anon const, but that's not happening. Specifically, `visit_const` on `Generalizer` should be updated to be similar to `visit_ty`. r? @BoxyUwU

…risDenton Implement stdio FD constants Tracking issue: rust-lang#150836

@JonathanBrouwer

…erence, r=jonathanbrouwer Port `rustc_strict_coherence` to the new attribute parser r? @JonathanBrouwer

@JonathanBrouwer

…ant-dtor, r=jonathanbrouwer Port `rustc_insignificant_dtor` r? @JonathanBrouwer Second commit removes it from an impl in std. I looked, and I really think it had no effect in the past. We only look for this attr on ADTs...

Zalathar · 2026-02-09T03:32:24Z

Rollup of everything.

@bors r+ rollup=never p=5

rust-bors · 2026-02-09T03:32:26Z

📌 Commit 7cb4501 has been approved by Zalathar

It is now in the queue for this repository.

rust-bors · 2026-02-09T09:27:03Z

☀️ Test successful - CI
Approved by: Zalathar
Duration: 3h 27m 3s
Pushing 4cd4c18 to main...

rust-timer · 2026-02-09T09:28:13Z

📌 Perf builds for each rolled up PR:

PR#	Message	Perf Build Sha
#150823	Implement MVP for opaque generic const arguments	`4c4aeb622e119e2c21e6478991fba18a7cfe16a9` (link)
#152071	Implement stdio FD constants	`20cac3bcbe353b7bf7ca49e7d64a64e02c42df20` (link)
#152171	Port `rustc_strict_coherence` to the new attribute parser	`0d9063cb6ffc54e5e98f87c95418485c043db910` (link)
#152291	Port `rustc_insignificant_dtor`	`0e58b8ab8da9f6b53fc78401de4a2659e2405a57` (link)

previous master: 39219ceb97

In the case of a perf regression, run the following command for each PR you suspect might be the cause: @rust-timer build $SHA

github-actions · 2026-02-09T09:29:58Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 39219ce (parent) -> 4cd4c18 (this PR)

Test differences

Show 88 test diffs

Stage 1

[ui] tests/ui/const-generics/ogca/basic-fail.rs: [missing] -> pass (J0)
[ui] tests/ui/const-generics/ogca/basic.rs: [missing] -> pass (J0)
[ui] tests/ui/const-generics/ogca/coherence-ambiguous.rs: [missing] -> pass (J0)
[ui] tests/ui/const-generics/ogca/rhs-but-not-root.rs: [missing] -> pass (J0)
[ui] tests/ui/feature-gates/feature-gate-opaque-generic-const-args.rs: [missing] -> pass (J0)

Stage 2

[ui] tests/ui/const-generics/ogca/basic-fail.rs: [missing] -> pass (J1)
[ui] tests/ui/const-generics/ogca/basic.rs: [missing] -> pass (J1)
[ui] tests/ui/const-generics/ogca/coherence-ambiguous.rs: [missing] -> pass (J1)
[ui] tests/ui/const-generics/ogca/rhs-but-not-root.rs: [missing] -> pass (J1)
[ui] tests/ui/feature-gates/feature-gate-opaque-generic-const-args.rs: [missing] -> pass (J1)

Additionally, 78 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 4cd4c18438fa57e005ee2bf9b80634f3a12d2998 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

aarch64-apple: 3h 7m -> 2h 15m (-27.6%)
dist-aarch64-msvc: 1h 45m -> 1h 30m (-14.1%)
aarch64-gnu: 2h 3m -> 2h 17m (+10.9%)
pr-check-2: 39m 4s -> 42m 51s (+9.7%)
x86_64-gnu-debug: 1h 53m -> 2h 4m (+9.6%)
dist-aarch64-llvm-mingw: 1h 45m -> 1h 35m (-9.3%)
dist-i586-gnu-i586-i686-musl: 1h 28m -> 1h 36m (+8.4%)
dist-x86_64-apple: 1h 44m -> 1h 52m (+8.0%)
x86_64-msvc-ext3: 1h 41m -> 1h 49m (+7.4%)
x86_64-msvc-1: 2h 24m -> 2h 35m (+7.4%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2026-02-09T10:09:30Z

Finished benchmarking commit (4cd4c18): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (secondary -4.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.6%	[-4.6%, -4.6%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (primary -1.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.6%	[-1.6%, -1.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.6%	[-1.6%, -1.6%]	1

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 477.309s -> 473.075s (-0.89%)
Artifact size: 397.86 MiB -> 397.90 MiB (0.01%)

hanna-kruppe and others added 9 commits February 3, 2026 22:35

Implement stdio FD constants

8b5be2b

Port rustc_insignificant_dtor to the new attribute parser

f1b4c2a

remove from impl block in std

9d6e120

Port rustc_strict_coherence to the new attribute parser

2dda303

Rollup merge of rust-lang#152071 - hanna-kruppe:stdio-fd-consts, r=Ch…

11c7917

…risDenton Implement stdio FD constants Tracking issue: rust-lang#150836

Rollup merge of rust-lang#152171 - jdonszelmann:port-rustc-strict-coh…

12f0ef7

…erence, r=jonathanbrouwer Port `rustc_strict_coherence` to the new attribute parser r? @JonathanBrouwer

rust-bors bot added the rollup A PR which is a rollup label Feb 9, 2026

rust-bors bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 9, 2026

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rust-bors bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Feb 9, 2026

rust-bors bot merged commit 4cd4c18 into rust-lang:main Feb 9, 2026
12 checks passed

rustbot added this to the 1.95.0 milestone Feb 9, 2026

This was referenced Feb 9, 2026

Port rustc_reservation_impl to the new attribute parser #152180

Merged

Port rust_nonnull_optimization_guaranteed and rustc_do_not_const_check to the new attribute parser #152296

Open

Rollup of 2 pull requests #152379

Closed

Zalathar deleted the rollup-wDsfoHs branch February 9, 2026 09:34

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