cleanup borrowck, improve c-variadic handling by lcnr · Pull Request #160504 · rust-lang/rust

lcnr · 2026-08-04T11:46:08Z

The first commits of #160491. Hopefully all of them make sense.

It feels intuitive to me that the c-variadic region should be just another late-bound region and tracking region correctly for #160491 is otherwise a mess.

r? types

lcnr · 2026-08-04T11:46:46Z

@bors try @rust-timer queue

cleanup borrowck, improve c-variadic handling

rust-bors · 2026-08-04T13:52:30Z

☀️ Try build successful (CI)
Build commit: e60c57e (e60c57e6c2bc8ac7568f88f5f1643f4560cabba1)
Base parent: c9ff496 (c9ff496891c278ad660bc0ab85c1f0b72059464a)

oli-obk

r=me after perf

View changes since this review

oli-obk · 2026-08-04T15:17:42Z

-                        DefiningTy::Const(body_def_id.to_def_id(), args)
-                    }
-                }
+            BodyOwnerKind::Const { inline: true } => {


The commit message could say that inline is already set exactly by checking the above match arm guard

oli-obk · 2026-08-04T15:22:36Z

+    /// The bound variables for a given defining type. This differs from their usual bound vars
+    /// in that closures and coroutine closures have an additional `'env`, while C-variadic
+    /// functions have an additional region for their implicit `VaList` input.


why don't we generally give them those bound vars earlier?

because they are used by users of these closures and FnDefs. The fn-sig of a closure || { upvar += 1; } is fn() for users during type checking and for<'env> fn(&'env mut self) when borrow checking the closure.

We could eagerly infer closure signatures as for<'env> fn(<?closure_kind as ClosureKind::SelfTy<'env>) and then it's always consistent. I don't know how that would work with the &VaList argument which doesn't really exist anywhere. Though I do feel like using fn_sig for c-variadic functions is generally kinda messed up 🤔

rustbot · 2026-08-04T15:23:14Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

rust-timer · 2026-08-04T15:59:49Z

Finished benchmarking commit (e60c57e): comparison URL.

Overall result: ❌ regressions - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@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)	-	-	0
Regressions ❌ (secondary)	3.6%	[3.6%, 3.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 0.6%, secondary -0.7%)

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

	mean	range	count
Regressions ❌ (primary)	4.2%	[4.2%, 4.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-0.7%, -0.5%]	3
Improvements ✅ (secondary)	-0.7%	[-2.4%, -0.4%]	20
All ❌✅ (primary)	0.6%	[-0.7%, 4.2%]	4

Cycles

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)	1.5%	[0.4%, 4.3%]	6
Regressions ❌ (secondary)	0.7%	[0.4%, 1.3%]	6
Improvements ✅ (primary)	-2.7%	[-6.9%, -0.6%]	4
Improvements ✅ (secondary)	-1.8%	[-3.2%, -0.6%]	4
All ❌✅ (primary)	-0.1%	[-6.9%, 4.3%]	10

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.838s -> 488.617s (-0.25%)
Artifact size: 390.28 MiB -> 390.23 MiB (-0.01%)

The field of `BodyOwnerKind` is computed via the exact same way as this check.

lcnr · 2026-08-06T11:58:32Z

@bors r=oli-obk rollup

rust-bors · 2026-08-06T11:58:35Z

📌 Commit b326732 has been approved by oli-obk

It is now in the queue for this repository.

cleanup borrowck, improve c-variadic handling The first commits of rust-lang#160491. Hopefully all of them make sense. It feels intuitive to me that the `c-variadic` region should be just another late-bound region and tracking region correctly for rust-lang#160491 is otherwise a mess. r? types

Rollup of 14 pull requests Successful merges: - #150885 (Revive L4Re target) - #159643 (Add support for splatted function pointers) - #160433 (delegation: add support for wrapping of the return value with `From::from`) - #160530 (refactor handling of target features in Session) - #160606 (bootstrap: Store and use an explicit CheckKind in `check::Rustc`) - #160628 (fix ICE in `suggest_add_reference_to_arg` for non-callable items) - #160634 (miri subtree update) - #158904 (Fix FutureDropPoll shim for by-move async closures) - #160335 (dlopen offload) - #160445 (codegen: classify localized MSVC linker progress as linker_info) - #160504 (cleanup borrowck, improve c-variadic handling) - #160587 (Add regression test for associated type outlives bound at call site) - #160625 (platform-support/netbsd.md: No longer mention 8.x, due to EoL.) - #160636 (derive(Diagnostic): link to proper docs)

cleanup borrowck, improve c-variadic handling The first commits of rust-lang#160491. Hopefully all of them make sense. It feels intuitive to me that the `c-variadic` region should be just another late-bound region and tracking region correctly for rust-lang#160491 is otherwise a mess. r? types

…uwer Rollup of 21 pull requests Successful merges: - #159784 (Hint that memchr returns an in-bounds index) - #150885 (Revive L4Re target) - #159643 (Add support for splatted function pointers) - #160433 (delegation: add support for wrapping of the return value with `From::from`) - #160530 (refactor handling of target features in Session) - #160606 (bootstrap: Store and use an explicit CheckKind in `check::Rustc`) - #160628 (fix ICE in `suggest_add_reference_to_arg` for non-callable items) - #160634 (miri subtree update) - #157641 (Do not promote extern statics) - #158904 (Fix FutureDropPoll shim for by-move async closures) - #160103 (Add regression test for GAT bound mismatched type error) - #160335 (dlopen offload) - #160445 (codegen: classify localized MSVC linker progress as linker_info) - #160499 (rustc_resolve: move diagnostic attribute linting to attr parsing) - #160504 (cleanup borrowck, improve c-variadic handling) - #160577 (expand: Feature gate AST-based attribute macros on expressions and statements) - #160587 (Add regression test for associated type outlives bound at call site) - #160625 (platform-support/netbsd.md: No longer mention 8.x, due to EoL.) - #160636 (derive(Diagnostic): link to proper docs) - #160644 (Clean up some manual debug impls) - #160649 (move naked function ui tests)

cleanup borrowck, improve c-variadic handling The first commits of rust-lang#160491. Hopefully all of them make sense. It feels intuitive to me that the `c-variadic` region should be just another late-bound region and tracking region correctly for rust-lang#160491 is otherwise a mess. r? types

…uwer Rollup of 20 pull requests Successful merges: - #159784 (Hint that memchr returns an in-bounds index) - #150885 (Revive L4Re target) - #159643 (Add support for splatted function pointers) - #160433 (delegation: add support for wrapping of the return value with `From::from`) - #160530 (refactor handling of target features in Session) - #160606 (bootstrap: Store and use an explicit CheckKind in `check::Rustc`) - #160628 (fix ICE in `suggest_add_reference_to_arg` for non-callable items) - #160634 (miri subtree update) - #157641 (Do not promote extern statics) - #158904 (Fix FutureDropPoll shim for by-move async closures) - #160103 (Add regression test for GAT bound mismatched type error) - #160335 (dlopen offload) - #160445 (codegen: classify localized MSVC linker progress as linker_info) - #160499 (rustc_resolve: move diagnostic attribute linting to attr parsing) - #160504 (cleanup borrowck, improve c-variadic handling) - #160577 (expand: Feature gate AST-based attribute macros on expressions and statements) - #160587 (Add regression test for associated type outlives bound at call site) - #160625 (platform-support/netbsd.md: No longer mention 8.x, due to EoL.) - #160636 (derive(Diagnostic): link to proper docs) - #160644 (Clean up some manual debug impls)

cleanup borrowck, improve c-variadic handling The first commits of rust-lang#160491. Hopefully all of them make sense. It feels intuitive to me that the `c-variadic` region should be just another late-bound region and tracking region correctly for rust-lang#160491 is otherwise a mess. r? types

…uwer Rollup of 28 pull requests Successful merges: - #159784 (Hint that memchr returns an in-bounds index) - #160673 (Improve `canonical_param_env_cache`) - #150885 (Revive L4Re target) - #159643 (Add support for splatted function pointers) - #160433 (delegation: add support for wrapping of the return value with `From::from`) - #160530 (refactor handling of target features in Session) - #160606 (bootstrap: Store and use an explicit CheckKind in `check::Rustc`) - #160628 (fix ICE in `suggest_add_reference_to_arg` for non-callable items) - #160683 (Add regression test for unknown feaeture name reported with other errors) - #157641 (Do not promote extern statics) - #158904 (Fix FutureDropPoll shim for by-move async closures) - #159816 (added note/help about iterator invalidation when mutating a collection inside a for loop) - #160103 (Add regression test for GAT bound mismatched type error) - #160335 (dlopen offload) - #160445 (codegen: classify localized MSVC linker progress as linker_info) - #160499 (rustc_resolve: move diagnostic attribute linting to attr parsing) - #160504 (cleanup borrowck, improve c-variadic handling) - #160577 (expand: Feature gate AST-based attribute macros on expressions and statements) - #160587 (Add regression test for associated type outlives bound at call site) - #160625 (platform-support/netbsd.md: No longer mention 8.x, due to EoL.) - #160633 (delegation: fix determining wrong `FnKind` when delegation is inside const arg) - #160636 (derive(Diagnostic): link to proper docs) - #160644 (Clean up some manual debug impls) - #160649 (move naked function ui tests) - #160672 (Improve `MaybeLiveLocals`) - #160693 (Add branch config for perf. unrolling in bors) - #160696 (rustc_codegen_llvm: handle sm_101* features being an alias) - #160706 (renovate: clarify that vulnerability PRs are opened automatically)

Rollup merge of #160504 - lcnr:borrowck-cleanup, r=oli-obk cleanup borrowck, improve c-variadic handling The first commits of #160491. Hopefully all of them make sense. It feels intuitive to me that the `c-variadic` region should be just another late-bound region and tracking region correctly for #160491 is otherwise a mess. r? types

make DefiningTy independent of borrowck

9ff75a7

rustbot assigned oli-obk Aug 4, 2026

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. labels Aug 4, 2026

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Aug 4, 2026

rust-bors Bot pushed a commit that referenced this pull request Aug 4, 2026

Auto merge of #160504 - lcnr:borrowck-cleanup, r=<try>

e60c57e

cleanup borrowck, improve c-variadic handling

lcnr mentioned this pull request Aug 4, 2026

move implied bounds computation out of borrowck #160491

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lcnr force-pushed the borrowck-cleanup branch from cb29ba5 to 1860072 Compare August 4, 2026 11:51

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rustbot 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 Aug 4, 2026

rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Aug 4, 2026

lcnr added 2 commits August 6, 2026 13:56

cleanup DefiningTy::new

c1af195

The field of `BodyOwnerKind` is computed via the exact same way as this check.

make the c_variadic region late bound

b326732

lcnr force-pushed the borrowck-cleanup branch from 1860072 to b326732 Compare August 6, 2026 11:58

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 6, 2026

JonathanBrouwer mentioned this pull request Aug 6, 2026

Rollup of 11 pull requests #160647

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JonathanBrouwer mentioned this pull request Aug 6, 2026

Rollup of 10 pull requests #160654

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jhpratt mentioned this pull request Aug 7, 2026

Rollup of 14 pull requests #160661

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jhpratt mentioned this pull request Aug 7, 2026

Rollup of 14 pull requests #160667

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JonathanBrouwer mentioned this pull request Aug 7, 2026

Rollup of 21 pull requests #160678

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JonathanBrouwer mentioned this pull request Aug 7, 2026

Rollup of 20 pull requests #160682

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jhpratt mentioned this pull request Aug 7, 2026

Rollup of 30 pull requests #160721

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JonathanBrouwer mentioned this pull request Aug 7, 2026

Rollup of 28 pull requests #160725

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rust-bors Bot merged commit ec8ac07 into rust-lang:main Aug 8, 2026
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rustbot added this to the 1.99.0 milestone Aug 8, 2026

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cleanup borrowck, improve c-variadic handling - #160504

cleanup borrowck, improve c-variadic handling#160504
rust-bors[bot] merged 3 commits into
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lcnr:borrowck-cleanup

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Overall result: ❌ regressions - no action needed

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