Rollup of 3 pull requests #150582

jhpratt · 2026-01-02T04:27:56Z

Successful merges:

Make asm_experimental_arch work in allow_internal_unstable macros #150073 (Make asm_experimental_arch work in allow_internal_unstable macros)
resolve: Preserve binding scopes in ambiguity errors #150445 (resolve: Preserve binding scopes in ambiguity errors)
Document panic! in Iterator::last for #149707 #150580 (Document panic! in Iterator::last for Document panic! for Iterator::last (Repeat) #149707)

r? @ghost
@rustbot modify labels: rollup

It allows to get rid of `AmbiguityErrorMisc` and `Flags`.

Added a `# Panics` section to `Iterator::last` to match `Iterator::count`, after the change made in Rust 1.92.0 where now `std::iter::Repeat` panics in these methods instead of doing an infinite `loop`. Cites rust-lang#149707

…erimental-arch, r=nnethercote Make `asm_experimental_arch` work in `allow_internal_unstable` macros This change makes it possible to use unstable `asm!`, usually requiring `feature(asm_experimental_arch)`, in proc-macros with the `allow_internal_unstable` attribute. The test was added on a target where `asm!` is unstable: Wasm. However, this affects *any* target with an unstable `asm!` implementation.

resolve: Preserve binding scopes in ambiguity errors It allows to get rid of `AmbiguityErrorMisc`, `Flags` and `extern_prelude_flag_binding`. Also keep all encountered bindings in `resolve_ident_in_scope_set`, it allows to get rid of `extern_prelude_item_binding`. This also unblocks rust-lang#149681 because the newly preserved data will help to fix the regressions in rust-lang#149681 (comment) in a reasonable way.

Document `panic!` in `Iterator::last` for rust-lang#149707 This PR adds a section `# Panics` to the method `Iterator::last` equal to the section `# Panics` of the method `Iterator::count`, because now, after the changes made in Rust 1.92.0, both methods in `std::iter::Repeat` panics instead of doing an infinite loop. `Iterator::count` already has documentation for this behavior ("This function might panic if the iterator has more than `usize::MAX` elements."), but `Iterator::last` does not. This PR adds documentation for this panic in the same way as `Iterator::count` does. Issue: rust-lang#149707

jhpratt · 2026-01-02T04:28:05Z

@bors r+ rollup=never p=3

bors · 2026-01-02T04:28:07Z

📌 Commit 9c5bdbd has been approved by jhpratt

It is now in the queue for this repository.

bors · 2026-01-02T05:37:49Z

⌛ Testing commit 9c5bdbd with merge 1b43252...

bors · 2026-01-02T08:57:41Z

☀️ Test successful - checks-actions
Approved by: jhpratt
Pushing 1b43252 to main...

rust-timer · 2026-01-02T08:58:34Z

📌 Perf builds for each rolled up PR:

PR#	Message	Perf Build Sha
#150073	Make `asm_experimental_arch` work in `allow_internal_unstab…	`02340827895864c97a9028531946cbec54cc60a6` (link)
#150445	resolve: Preserve binding scopes in ambiguity errors	`85f8996116ce925a3b58392fb9eac9f82d4ec869` (link)
#150580	Document `panic!` in `Iterator::last` for #149707	`b32c51490e1aab436a16d7a8938f3e6b96e36412` (link)

previous master: a47f4dfd7f

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 · 2026-01-02T09:00:29Z

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 a47f4df (parent) -> 1b43252 (this PR)

Test differences

Show 588 test diffs

Stage 1

[ui] tests/ui/internal/internal-unstable-asm-experimental-arch.rs: [missing] -> ignore (only executed when the target is wasm32-wasip1) (J0)

Stage 2

[ui] tests/ui/internal/internal-unstable-asm-experimental-arch.rs: [missing] -> ignore (only executed when the target is wasm32-wasip1) (J1)

Additionally, 586 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 1b4325211c3228dd10eea12e9b3f749f87363d95 --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

dist-x86_64-apple: 6896.7s -> 8694.5s (+26.1%)
x86_64-gnu-gcc: 3416.3s -> 2770.4s (-18.9%)
aarch64-gnu-llvm-20-2: 3196.4s -> 2775.3s (-13.2%)
pr-check-1: 1934.7s -> 1691.7s (-12.6%)
i686-gnu-nopt-1: 8069.4s -> 7122.5s (-11.7%)
i686-gnu-2: 5946.0s -> 5302.3s (-10.8%)
i686-gnu-1: 8162.1s -> 7394.5s (-9.4%)
aarch64-gnu: 7243.4s -> 7875.4s (+8.7%)
x86_64-gnu-miri: 4954.8s -> 4556.7s (-8.0%)
aarch64-gnu-debug: 4293.2s -> 3955.5s (-7.9%)

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 · 2026-01-02T09:39:44Z

Finished benchmarking commit (1b43252): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

If the regression was expected or you think it can be justified,
please write a comment with sufficient written justification, and add
@rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
If you think that you know of a way to resolve the regression, try to create
a new PR with a fix for the regression.
If you do not understand the regression or you think that it is just noise,
you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	0.1%	[0.1%, 0.2%]	2
Improvements ✅ (primary)	-0.1%	[-0.2%, -0.1%]	4
Improvements ✅ (secondary)	-0.7%	[-1.8%, -0.1%]	3
All ❌✅ (primary)	-0.1%	[-0.2%, 0.2%]	5

Max RSS (memory usage)

Results (primary 0.3%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[1.1%, 1.9%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.2%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[-2.2%, 1.9%]	3

Cycles

Results (primary 0.5%, secondary -2.0%)

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

	mean	range	count
Regressions ❌ (primary)	2.6%	[2.6%, 2.6%]	1
Regressions ❌ (secondary)	2.6%	[2.6%, 2.6%]	1
Improvements ✅ (primary)	-1.7%	[-1.7%, -1.7%]	1
Improvements ✅ (secondary)	-6.5%	[-6.5%, -6.5%]	1
All ❌✅ (primary)	0.5%	[-1.7%, 2.6%]	2

Binary size

Results (primary 0.0%, secondary 0.0%)

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

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	7
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	7

Bootstrap: 473.624s -> 472.736s (-0.19%)
Artifact size: 390.78 MiB -> 390.80 MiB (0.01%)

Kobzol · 2026-01-06T08:22:21Z

Tiny changes, overall it's a wash.

@rustbot label: +perf-regression-triaged

daxpedda and others added 7 commits December 16, 2025 22:39

Make asm_experimental_arch work in allow_internal_unstable macros

96c165b

resolve: Preserve binding scopes in ambiguity errors

1c7d3f0

It allows to get rid of `AmbiguityErrorMisc` and `Flags`.

resolve: Keep all encountered bindings in resolve_ident_in_scope_set

b018f42

library: Document panic condition for Iterator::last

d68c980

Added a `# Panics` section to `Iterator::last` to match `Iterator::count`, after the change made in Rust 1.92.0 where now `std::iter::Repeat` panics in these methods instead of doing an infinite `loop`. Cites rust-lang#149707

bors 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 Jan 2, 2026

bors added the merged-by-bors This PR was explicitly merged by bors. label Jan 2, 2026

bors merged commit 1b43252 into rust-lang:main Jan 2, 2026
12 checks passed

rustbot added this to the 1.94.0 milestone Jan 2, 2026

jhpratt deleted the rollup-3mal3wc branch January 2, 2026 09:03

bors mentioned this pull request Jan 2, 2026

Explicitly export core and std macros #139493

Merged

rustbot added the perf-regression Performance regression. label Jan 2, 2026

This was referenced Jan 2, 2026

resolve: Partially convert ambiguous_glob_imports lint into a hard error #149195

Open

resolve: Split Scope::Module into two scopes for non-glob and glob bindings #149681

Merged

resolve: Rename "name bindings" to "name declarations" #150521

Merged

KaiTomotake mentioned this pull request Jan 6, 2026

Document panic! for Iterator::last (Repeat) #149707

Open

rustbot added the perf-regression-triaged The performance regression has been triaged. label Jan 6, 2026

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Rollup of 3 pull requests #150582

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jhpratt commented Jan 2, 2026 •

edited by rustbot

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Test differences

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Job duration changes

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rust-timer commented Jan 2, 2026

Overall result: ❌✅ regressions and improvements - please read the text below

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