Move check_rustc_must_implement_one_of validation to attribute parser by darkraider01 · Pull Request #163980 · rust-lang/rust

darkraider01 · 2026-10-08T09:49:55Z

Moves the remaining rustc_must_implement_one_of validation from rustc_passes::check_attr into RustcMustImplementOneOfParser::finalize_check using AST trait information available through FinalizeCheckContext::target_item.

The duplicate-name validation was already migrated in #160412. This completes the remaining associated-item and default-implementation checks.

Related: #153101, #131229, #160412

rustbot · 2026-10-08T11:11:06Z

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

rustbot · 2026-10-08T11:11:10Z

r? @wesleywiser

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darkraider01 · 2026-10-08T11:35:16Z

            match ctxt {
                visit::AssocCtxt::Trait => {
-                    self.replace_with_dummy(item, AssocItemKind::MacCall, AstOwner::TraitItem)
+                    self.insert(item.id, AstOwner::TraitItem(Box::new(item.clone())));


The old replace_with_dummy was replacing the trait items with MacCall placeholders, so finalize_check couldn't actually inspect them through target_item.

This keeps the original items in the trait while still indexing the cloned ones separately for lowering.

The downside is that we're cloning trait items even when the attribute isn't used. I couldn't find a simpler way to reuse the existing infrastructure here, but I'm open to suggestions.

View changes since the review

Edit: (This approach is suggested by llm, since i couldn't come with a better/simplied solution) Maybe another option could be to keep the original trait items only for traits with #[rustc_must_implement_one_of] , and use the existing placeholders everywhere else. That would still involve cloning, but limit it to traits that actually need the check. Not sure how neatly it would fit into the indexer, especially with nested traits, but it might be worth exploring.

I think both options might be terrible for performance, let's check.
It also just doesn't feel like a great solution, it might be better to just keep the check in rustc_passes if this is needed

I've started a small experiment here that might make this code nice if perf allows: #164980

I'm not expecting that PR to be accepted tho

Tried this with #163980 locally and it works without cloning the trait items. I just dropped the cloning hunk and kept your indexer as-is. Thank you!!!
Edit: heres the branch if you'd like to inspect https://github.com/darkraider01/rust/tree/experiment-ast-retention-164980

darkraider01 · 2026-10-08T11:35:44Z

+                    _ => {
+                        cx.emit_err(diagnostics::MustImplementNotFunction {
+                            span: item.span,
+                            span_note: diagnostics::MustImplementNotFunctionSpanNote {


Keeping delegation as a valid case here since it lowers to TraitFn::Provided, which the old check already accepted.

I added tests for both normal and renamed delegation as well.

View changes since the review

darkraider01 · 2026-10-08T11:36:04Z

+            panic!("expected trait AST target item for Target::Trait");
+        };
+
+        let fn_names =


Kept the full Ident comparison here rather than just matching names, since the old check did the same.

Added a couple of macro tests to make sure the hygiene behavior stays the same.

View changes since the review

JonathanBrouwer · 2026-10-09T07:57:48Z

r? me

JonathanBrouwer · 2026-10-25T16:56:54Z

(Sorry for taking so long to review this, I've been away for a bit due to conferences and illness, I should get to this in a day or two)

rustbot · 2026-10-26T08:05:10Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

JonathanBrouwer · 2026-10-26T10:32:10Z

@bors try @rust-timer queuee

rust-timer · 2026-10-26T10:32:14Z

Unknown rust-timer command: queuee

JonathanBrouwer · 2026-10-26T10:32:20Z

@rust-timer queue

…oundary, r=<try> Move check_rustc_must_implement_one_of validation to attribute parser

rust-bors · 2026-10-26T11:31:08Z

☀️ Try build successful (CI)
Build commit: b1e6bae (b1e6bae0c860da20f7d5a54118a16d884694aaf0)
Base parent: aaf324d (aaf324d50a7dcb17aae7f2a37e15ff143d980c6e)

rust-timer · 2026-10-26T13:10:25Z

Finished benchmarking commit (b1e6bae): comparison URL.

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

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

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=iffy 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)	0.2%	[0.2%, 0.3%]	3
Regressions ❌ (secondary)	0.4%	[0.2%, 0.7%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.5%, -0.0%]	12
All ❌✅ (primary)	0.2%	[0.2%, 0.3%]	3

Max RSS (memory usage)

Results (primary 0.3%, secondary 0.5%)

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

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.4%, 1.4%]	8
Regressions ❌ (secondary)	0.5%	[0.5%, 0.5%]	1
Improvements ✅ (primary)	-0.6%	[-0.7%, -0.4%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[-0.7%, 1.4%]	11

Cycles

Results (primary -0.5%, secondary -0.5%)

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

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.4%, 0.9%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.9%	[-1.9%, -0.6%]	11
Improvements ✅ (secondary)	-0.5%	[-0.7%, -0.4%]	2
All ❌✅ (primary)	-0.5%	[-1.9%, 0.9%]	15

Binary size

Results (primary 0.1%, 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)	0.1%	[0.0%, 0.2%]	64
Regressions ❌ (secondary)	0.1%	[0.0%, 0.3%]	56
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[0.0%, 0.2%]	64

Bootstrap: 488.092s -> 488.8s (0.15%)
Artifact size: 405.81 MiB -> 406.04 MiB (0.06%)

JonathanBrouwer · 2026-10-26T13:11:51Z

The include-blob improvements are noise, the regressions seem to be real

rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) 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 Oct 8, 2026

darkraider01 force-pushed the document-must-implement-one-of-boundary branch from 2828fd1 to 5792ac6 Compare October 8, 2026 10:29

darkraider01 changed the title ~~Document check_rustc_must_implement_one_of boundary in check_attr~~ Move check_rustc_must_implement_one_of validation to attribute parser Oct 8, 2026

darkraider01 force-pushed the document-must-implement-one-of-boundary branch from 5792ac6 to ab04b05 Compare October 8, 2026 11:10

darkraider01 marked this pull request as ready for review October 8, 2026 11:11

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 Oct 8, 2026

rustbot assigned wesleywiser Oct 8, 2026

darkraider01 marked this pull request as draft October 8, 2026 11:14

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 Oct 8, 2026

darkraider01 commented Oct 8, 2026

View reviewed changes

darkraider01 marked this pull request as ready for review October 8, 2026 11:47

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 Oct 8, 2026

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rustbot assigned JonathanBrouwer and unassigned wesleywiser Oct 9, 2026