Implement cromulent Copy closure captures by Jules-Bertholet · Pull Request #163717 · rust-lang/rust

Jules-Bertholet · 2026-10-03T20:04:16Z

@rustbot label T-lang A-closures needs-fcp

rust-timer · 2026-10-06T04:19:42Z

Finished benchmarking commit (5692858): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@rustbot label: -S-waiting-on-perf +perf-regression

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)	1.0%	[0.3%, 1.7%]	2
Regressions ❌ (secondary)	0.9%	[0.0%, 1.6%]	12
Improvements ✅ (primary)	-0.7%	[-5.0%, -0.2%]	261
Improvements ✅ (secondary)	-0.8%	[-6.8%, -0.1%]	214
All ❌✅ (primary)	-0.6%	[-5.0%, 1.7%]	263

Max RSS (memory usage)

Results (primary -2.0%, secondary -1.8%)

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

	mean	range	count
Regressions ❌ (primary)	3.0%	[2.4%, 3.6%]	2
Regressions ❌ (secondary)	3.2%	[2.1%, 4.2%]	2
Improvements ✅ (primary)	-2.7%	[-6.3%, -0.8%]	15
Improvements ✅ (secondary)	-3.2%	[-6.0%, -0.5%]	7
All ❌✅ (primary)	-2.0%	[-6.3%, 3.6%]	17

Cycles

Results (primary -2.2%, secondary -4.7%)

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

	mean	range	count
Regressions ❌ (primary)	3.4%	[2.1%, 4.6%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.2%	[-5.6%, -1.3%]	11
Improvements ✅ (secondary)	-4.7%	[-6.6%, -3.8%]	8
All ❌✅ (primary)	-2.2%	[-5.6%, 4.6%]	13

Binary size

Results (primary 0.1%, secondary -0.3%)

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

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.1%, 1.1%]	19
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.3%	[-0.9%, -0.0%]	17
Improvements ✅ (secondary)	-0.3%	[-0.5%, -0.0%]	13
All ❌✅ (primary)	0.1%	[-0.9%, 1.1%]	36

Bootstrap: 489.541s -> 492.774s (0.66%)
Artifact size: 408.63 MiB -> 408.96 MiB (0.08%)

mejrs · 2026-10-06T20:36:14Z

@bors try

…es, r=<try> Implement cromulent Copy closure captures

rust-bors · 2026-10-06T21:37:38Z

☀️ Try build successful (CI)
Build commit: 83e3885 (83e388551a68240a8add01574724ea840a7bbc2a)
Base parent: 8d1a764 (8d1a76430406c877b35d0b627e7f796dcf0dfeca)

mejrs · 2026-10-07T07:59:45Z

@craterbot check

craterbot · 2026-10-07T08:00:00Z

👌 Experiment pr-163717 created and queued.
🤖 Automatically detected try build 83e3885
⚠️ Try build based on commit 1ddfd18, but latest commit is 7247983. Did you forget to make a new try build?
🔍 You can check out the queue and this experiment's details.

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@rustbot

…=Kobzol Remove redundant closure in bootstrap My PR rust-lang#163717 would make Clippy start linting `redundant_closure_for_method_calls` here; let's get ahead of that. @rustbot label T-bootstrap @rustbot ready r? bootstrap

@rustbot

…=Kobzol Remove redundant closure in bootstrap My PR rust-lang#163717 would make Clippy start linting `redundant_closure_for_method_calls` here; let's get ahead of that. @rustbot label T-bootstrap @rustbot ready r? bootstrap

@rustbot

…=Kobzol Remove redundant closure in bootstrap My PR rust-lang#163717 would make Clippy start linting `redundant_closure_for_method_calls` here; let's get ahead of that. @rustbot label T-bootstrap @rustbot ready r? bootstrap

@rustbot

Rollup merge of #163905 - Jules-Bertholet:bootstrap-tweak, r=Kobzol Remove redundant closure in bootstrap My PR #163717 would make Clippy start linting `redundant_closure_for_method_calls` here; let's get ahead of that. @rustbot label T-bootstrap @rustbot ready r? bootstrap

@rustbot

Remove redundant closure in bootstrap My PR rust-lang/rust#163717 would make Clippy start linting `redundant_closure_for_method_calls` here; let's get ahead of that. @rustbot label T-bootstrap @rustbot ready r? bootstrap

Jules-Bertholet · 2026-10-08T14:03:17Z

@@ -13,7 +13,7 @@
 #[no_mangle]
 pub fn vec_append_with_temp_alloc(dst: &mut Vec<u8>, src: &[u8]) {


I have no idea what is going on here. See https://rust-lang.zulipchat.com/#narrow/channel/182449-t-compiler.2Fhelp/topic/Help.20debugging.20MIR.20inlining.20change/with/630027294 for discussion

View changes since the review

Implements RFC 4011.