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rustc_resolve: improve const generic errors#152913

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rust-bors[bot] merged 1 commit intorust-lang:mainfrom
Unique-Usman:ua/constnottype
Mar 20, 2026
Merged

rustc_resolve: improve const generic errors#152913
rust-bors[bot] merged 1 commit intorust-lang:mainfrom
Unique-Usman:ua/constnottype

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@Unique-Usman Unique-Usman commented Feb 20, 2026 •
edited by rustbot
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@rustbot 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 Feb 20, 2026
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r? @JonathanBrouwer

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Unique-Usman commented Feb 20, 2026

r? @estebank

@rustbot rustbot assigned estebank and unassigned JonathanBrouwer Feb 20, 2026
@Unique-Usman Unique-Usman marked this pull request as draft February 20, 2026 14:49
@rustbot 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 Feb 20, 2026
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compiler/rustc_resolve/src/build_reduced_graph.rs
.struct_constructors
.insert(local_def_id, (ctor_res, ctor_vis.to_def_id(), ret_fields));
}
self.r.struct_generics.insert(local_def_id, generics.clone());
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Let's see if we can struct_generics store references. That should keep mem usage to a minimum.

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@Unique-Usman Unique-Usman Mar 6, 2026

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Noted.

compiler/rustc_resolve/src/late.rs
Comment on lines +4472 to +4475
if let Some(const_err) = const_err {
err.cancel();
err = const_err;
}
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This is currently inactive, right? const_err isn't None anywhere right now?

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const_err is actually always None except in the case of where we add the error we just introduce see it here -> https://github.com/rust-lang/rust/pull/152913/changes#diff-2c81e6d8048a31a3ce43f30181aaa037e0ad0076e7aee67792ca993f28c75ac3R3440-R3441

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it is to prevent the type error from showing up.

@Unique-Usman Unique-Usman requested a review from estebank March 6, 2026 17:35
@Unique-Usman Unique-Usman marked this pull request as ready for review March 6, 2026 17:35
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rustbot commented Mar 6, 2026

HIR ty lowering was modified

cc @fmease

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Unique-Usman commented Mar 10, 2026

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tests/ui/const-generics/assoc_const_as_type_argument.stderr Outdated
@@ -4,18 +4,19 @@ error[E0575]: expected associated type, found associated constant `Trait::ASSOC`
LL | bar::<<T as Trait>::ASSOC>();
| ^^^^^^^^^^^^^^^^^^^ not a associated type

error[E0747]: unresolved item provided when a constant was expected
--> $DIR/assoc_const_as_type_argument.rs:8:11
error[E0284]: type annotations needed
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It is unfortunate that after silencing E0747 we end up with these inference errors instead...

I think we can split the work into two PRs: one silencing the unnecessary/redundant resolve error ("unresolved item when X was expected") and another for the appropriate const generic suggestions. That would make things easier to review and evolve on isolation.

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Yeah, thanks. we can resolve the E0747 error after getting this pr merged. I already update the patch to not silence the E0747 for now.

@Unique-Usman Unique-Usman requested a review from estebank March 16, 2026 18:51
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estebank commented Mar 16, 2026

@bors r+

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📌 Commit 54aebeb has been approved by estebank

It is now in the queue for this repository.

@rust-bors 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-review Status: Awaiting review from the assignee but also interested parties. labels Mar 16, 2026
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rust-bors bot pushed a commit that referenced this pull request Mar 16, 2026
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Auto merge of #152913 - Unique-Usman:ua/constnottype, r=estebank
f80d097 
rustc_resolve: improve const generic errors
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@rust-bors rust-bors bot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Mar 17, 2026
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rust-bors bot commented Mar 17, 2026

💔 Test for f80d097 failed: CI. Failed job:

@Unique-Usman
rustc_resolve: improve const generic errors
f60b649 
Signed-off-by: Usman Akinyemi <usmanakinyemi202@gmail.com>
@rust-bors rust-bors bot 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 Mar 19, 2026
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rustbot commented Mar 19, 2026

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.

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estebank commented Mar 19, 2026

@bors r+

The error seems to be spurious/not related to this PR. It was rebased on top of a more recent main.

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📌 Commit f60b649 has been approved by estebank

It is now in the queue for this repository.

@rust-bors 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 Mar 19, 2026
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@rust-bors rust-bors bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Mar 20, 2026
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rust-bors bot commented Mar 20, 2026

☀️ Test successful - CI
Approved by: estebank
Duration: 3h 8m 58s
Pushing 76be1cc to main...

@rust-bors rust-bors bot merged commit 76be1cc into rust-lang:main Mar 20, 2026
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@rustbot rustbot added this to the 1.96.0 milestone Mar 20, 2026
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github-actions bot commented Mar 20, 2026

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 bcf3d36 (parent) -> 76be1cc (this PR)

Test differences

Show 3 test diffs

3 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 76be1cc4eef94daeab731ed9395a317b34d89d63 --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

  1. dist-apple-various: 1h 20m -> 1h 46m (+33.0%)
  2. pr-check-1: 26m 6s -> 32m 29s (+24.5%)
  3. test-various: 1h 42m -> 2h 5m (+22.5%)
  4. dist-aarch64-msvc: 1h 33m -> 1h 53m (+22.0%)
  5. x86_64-gnu-llvm-22-2: 1h 23m -> 1h 39m (+18.9%)
  6. armhf-gnu: 1h 18m -> 1h 31m (+16.6%)
  7. aarch64-msvc-2: 1h 44m -> 2h (+15.3%)
  8. aarch64-apple: 2h 15m -> 2h 33m (+13.5%)
  9. x86_64-rust-for-linux: 45m 58s -> 51m 37s (+12.3%)
  10. x86_64-gnu-tools: 55m 12s -> 1h 1m (+12.0%)
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-bors rust-bors bot mentioned this pull request Mar 20, 2026
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rust-timer commented Mar 20, 2026

Finished benchmarking commit (76be1cc): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -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)		 0.1% [0.1%, 0.1%] 1
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 0.1% [0.1%, 0.1%] 1

Max RSS (memory usage)

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)		 1.2% [1.2%, 1.2%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -1.8% [-1.8%, -1.8%] 1
All ❌✅ (primary) - - 0

Cycles

Results (secondary -2.7%)

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
Improvements ✅
(secondary)		 -2.7% [-3.0%, -2.4%] 2
All ❌✅ (primary) - - 0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 483.892s -> 481.595s (-0.47%)
Artifact size: 394.73 MiB -> 396.86 MiB (0.54%)

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