Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children by oli-obk · Pull Request #158360 · rust-lang/rust

oli-obk · 2026-06-24T15:08:19Z

Various things I noticed while figuring out how to best allow changing some borrowck errors into FCWs

cc @rust-lang/types for the typeck children stuff, in case I missed some memo and am undoing some work

r? @ghost need perf first

Instead of having to taint both infcx and root_cx, we always just taint infcx (which usually gets automatically tainted from emitting diagnostics), and at the end (before dropping the infcx) we move the taint over to the root_cx

…ame as their parent

oli-obk · 2026-06-24T15:08:36Z

@bors try @rust-timer queue

Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children

rust-bors · 2026-06-24T17:24:16Z

☀️ Try build successful (CI)
Build commit: 8860163 (886016386e639dff64ebf46c1eb188fba16235ea)
Base parent: f28ac76 (f28ac764c36004fa6a6e098d15b4016a838c13c6)

rust-timer · 2026-06-24T18:18:15Z

Finished benchmarking commit (8860163): 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
@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)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-0.1%	[-0.2%, -0.1%]	6
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.1%	[-0.2%, -0.1%]	6

Max RSS (memory usage)

Results (primary -5.3%)

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)	-5.3%	[-5.3%, -5.3%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-5.3%	[-5.3%, -5.3%]	1

Cycles

Results (secondary 2.9%)

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)	2.9%	[2.9%, 2.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 510.446s -> 505.876s (-0.90%)
Artifact size: 353.05 MiB -> 353.51 MiB (0.13%)

oli-obk · 2026-06-24T20:28:38Z

@rustbot reroll

lcnr · 2026-06-25T08:08:39Z

+            if count > 10 {
+                diag.note(format!("...and {} other attempted mutable borrows", count - 10));
+            }
+            self.buffer_error(diag);


existing: but this is confusing. we don't drop any later errors here, do we?

so if we have 15 buffered mut errors, we still emit 15 errors, don't we?

View changes since the review

There is one diagnostic per binding. If the binding has more than 10 mutable borrows, we don't emit a note for all of them. This is information already in the diag. unsure why we don't add the above not immediately when stopping to add more mutable borrow notes

ah no, this makes sense, we eagerly mutate the diagnostic and stop doing so when count > 10, but only want to add a single note telling us how many attempted mutable borrows there are

lcnr · 2026-06-25T08:11:56Z

+    if tcx.is_typeck_child(item.to_def_id()) {
+        return tcx.opaque_types_defined_by(tcx.local_parent(item));
+    }


alternative is to debug_assert this and make sure we never call it for typeck children 🤔 where do we currently use it for them

View changes since the review

That's a huge diff. I'll do that as a separate PR. We call param_env on the children's DefId all over the place

unless you want to work on it right away, would you mind opening an issue for this cleanup (or add a FIXME)

I already have a commit started, which is how I observed it was gonna be too much for this PR

lcnr

some nits and generally r=me, though maybe it would be nicer to instead not allow param_env and opaque_types_defined_by for typeck children because it feels like we should never do so and by ICEing eagerly we avoid potential bugs?

View changes since this review

lcnr · 2026-06-25T08:13:08Z

r? lcnr

…uwer Rollup of 6 pull requests Successful merges: - #158360 (Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children) - #157127 (cg_LLVM: Stop needing an alloca for volatile loads) - #158244 (Attribute docs `deprecated` , `warn`, `allow`, `cfg`, `deny`, and `forbid` ) - #158355 (Fixup the refactoring errors in #156246) - #158399 (std: truncate thread names on NetBSD) - #158430 (Guard clone suggestion against empty obligation errors)

@ghost

Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children Various things I noticed while figuring out how to best allow changing some borrowck errors into FCWs cc @rust-lang/types for the typeck children stuff, in case I missed some memo and am undoing some work r? @ghost need perf first

…uwer Rollup of 7 pull requests Successful merges: - #158360 (Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children) - #157127 (cg_LLVM: Stop needing an alloca for volatile loads) - #158244 (Attribute docs `deprecated` , `warn`, `allow`, `cfg`, `deny`, and `forbid` ) - #158355 (Fixup the refactoring errors in #156246) - #158361 (Move `check_ffi_pure` into the attribute parser) - #158399 (std: truncate thread names on NetBSD) - #158430 (Guard clone suggestion against empty obligation errors)

@ghost

Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children Various things I noticed while figuring out how to best allow changing some borrowck errors into FCWs cc @rust-lang/types for the typeck children stuff, in case I missed some memo and am undoing some work r? @ghost need perf first

…uwer Rollup of 11 pull requests Successful merges: - #153697 (Add arg splat experiment initial tuple impl) - #158360 (Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children) - #157127 (cg_LLVM: Stop needing an alloca for volatile loads) - #158376 (Suggest `>=` for `=>` typo in closure and call argument positions) - #158244 (Attribute docs `deprecated` , `warn`, `allow`, `cfg`, `deny`, and `forbid` ) - #158355 (Fixup the refactoring errors in #156246) - #158361 (Move `check_ffi_pure` into the attribute parser) - #158399 (std: truncate thread names on NetBSD) - #158418 (Eliminate double length check in `Vec::into_array`) - #158430 (Guard clone suggestion against empty obligation errors) - #158448 (Cleanup `NumBuffer` comment and replace `ilog(10)` with `ilog10()`)

…uwer Rollup of 15 pull requests Successful merges: - #153697 (Add arg splat experiment initial tuple impl) - #158360 (Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children) - #158438 (Use rigidness marker in fast_reject) - #157127 (cg_LLVM: Stop needing an alloca for volatile loads) - #158376 (Suggest `>=` for `=>` typo in closure and call argument positions) - #158185 (perf: Make stable_crate_ids reads lock-free after crate loading) - #158244 (Attribute docs `deprecated` , `warn`, `allow`, `cfg`, `deny`, and `forbid` ) - #158355 (Fixup the refactoring errors in #156246) - #158361 (Move `check_ffi_pure` into the attribute parser) - #158382 (Add safety section for SliceIndex::get_unchecked(mut)) - #158399 (std: truncate thread names on NetBSD) - #158418 (Eliminate double length check in `Vec::into_array`) - #158430 (Guard clone suggestion against empty obligation errors) - #158446 (Update Enzyme submodule) - #158448 (Cleanup `NumBuffer` comment and replace `ilog(10)` with `ilog10()`)

@ghost

Rollup merge of #158360 - oli-obk:borrowck-cleanups, r=lcnr Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children Various things I noticed while figuring out how to best allow changing some borrowck errors into FCWs cc @rust-lang/types for the typeck children stuff, in case I missed some memo and am undoing some work r? @ghost need perf first

…uwer Rollup of 15 pull requests Successful merges: - rust-lang/rust#153697 (Add arg splat experiment initial tuple impl) - rust-lang/rust#158360 (Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children) - rust-lang/rust#158438 (Use rigidness marker in fast_reject) - rust-lang/rust#157127 (cg_LLVM: Stop needing an alloca for volatile loads) - rust-lang/rust#158376 (Suggest `>=` for `=>` typo in closure and call argument positions) - rust-lang/rust#158185 (perf: Make stable_crate_ids reads lock-free after crate loading) - rust-lang/rust#158244 (Attribute docs `deprecated` , `warn`, `allow`, `cfg`, `deny`, and `forbid` ) - rust-lang/rust#158355 (Fixup the refactoring errors in rust-lang/rust#156246) - rust-lang/rust#158361 (Move `check_ffi_pure` into the attribute parser) - rust-lang/rust#158382 (Add safety section for SliceIndex::get_unchecked(mut)) - rust-lang/rust#158399 (std: truncate thread names on NetBSD) - rust-lang/rust#158418 (Eliminate double length check in `Vec::into_array`) - rust-lang/rust#158430 (Guard clone suggestion against empty obligation errors) - rust-lang/rust#158446 (Update Enzyme submodule) - rust-lang/rust#158448 (Cleanup `NumBuffer` comment and replace `ilog(10)` with `ilog10()`)

JonathanBrouwer · 2026-06-27T11:07:54Z

@rust-timer build 6c2bd6b
Perf run for #158455

rust-timer · 2026-06-27T13:36:01Z

Finished benchmarking commit (6c2bd6b): 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
@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)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	0.1%	[0.1%, 0.2%]	2
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.1%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.0%	[-0.1%, 0.2%]	3

Max RSS (memory usage)

Results (primary -2.2%, 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
Regressions ❌ (secondary)	6.1%	[6.1%, 6.1%]	1
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.1%]	2
Improvements ✅ (secondary)	-2.0%	[-2.4%, -1.5%]	3
All ❌✅ (primary)	-2.2%	[-2.2%, -2.1%]	2

Cycles

Results (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
Regressions ❌ (secondary)	3.6%	[2.1%, 6.6%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.7%	[-9.5%, -1.5%]	5
All ❌✅ (primary)	-	-	0

Binary size

Results (primary -0.0%, secondary -0.1%)

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)	-0.0%	[-0.0%, -0.0%]	3
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	3
All ❌✅ (primary)	-0.0%	[-0.0%, -0.0%]	3

Bootstrap: 486.597s -> 484.848s (-0.36%)
Artifact size: 395.64 MiB -> 393.55 MiB (-0.53%)

oli-obk added 6 commits June 24, 2026 09:08

Move some methods that only need the region context onto that

b429456

Consistently taint root cx

7ebb859

Instead of having to taint both infcx and root_cx, we always just taint infcx (which usually gets automatically tainted from emitting diagnostics), and at the end (before dropping the infcx) we move the taint over to the root_cx

Remove some unnecessary mutabilities

f44093d

Typeck children always have the same param env as their parent

7102a6c

Don't compute opaque types for typeck children. They are always the s…

7cb94f0

…ame as their parent

Add a convenience helper for doing type ops

7ccc34f

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 24, 2026

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rust-bors Bot pushed a commit that referenced this pull request Jun 24, 2026

Auto merge of #158360 - oli-obk:borrowck-cleanups, r=<try>

8860163

Various borrowck cleanups and param_env/opaque_types_defined_by query simplifications for typeck children

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Jun 24, 2026

oli-obk marked this pull request as ready for review June 24, 2026 20:27

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 24, 2026

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rustbot assigned davidtwco Jun 24, 2026

lcnr reviewed Jun 25, 2026

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rustbot assigned lcnr Jun 25, 2026

JonathanBrouwer mentioned this pull request Jun 26, 2026

Rollup of 6 pull requests #158437

Closed

JonathanBrouwer mentioned this pull request Jun 26, 2026

Rollup of 7 pull requests #158442

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JonathanBrouwer mentioned this pull request Jun 26, 2026

Rollup of 11 pull requests #158450

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JonathanBrouwer mentioned this pull request Jun 26, 2026

Rollup of 15 pull requests #158455

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rust-bors Bot merged commit 64f56e7 into rust-lang:main Jun 27, 2026
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rustbot added this to the 1.98.0 milestone Jun 27, 2026

khyperia mentioned this pull request Jun 27, 2026

Support DefKind::InlineConst in ConstKind::Unevaluated #158375

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rust-timer commented Jun 24, 2026

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

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

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