Perform many const checks in typeck by oli-obk · Pull Request #149375 · rust-lang/rust

oli-obk · 2025-11-27T08:25:06Z

Some smaller diagnostic changes, the biggest ones avoided by #148641

We should be able to move various checks in mir const checking to using span_bug! instead of reporting an error, just like mir typeck does as a sanity check. I would like to start doing so separately though, as this PR is a big enough (in what effects it causes, pun intended).

r? @fee1-dead

rustbot · 2025-11-27T08:25:10Z

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

oli-obk · 2025-11-27T08:25:18Z

@bors try @rust-timer queue

Perform many const checks in typeck

oli-obk · 2025-11-27T08:26:20Z

tests/crashes/137187.rs

 //@ known-bug: #137187
+#![feature(const_trait_impl, const_ops)]
+
 use std::ops::Add;
-trait A where
-    *const Self: Add,
+const trait A where
+    *const Self: const Add,
 {
-    const fn b(c: *const Self) -> <*const Self as Add>::Output {
+    fn b(c: *const Self) -> <*const Self as Add>::Output {
        c + c
    }
 }
+
+fn main() {}


This produces the same ICE as before, but the changes were required to pass typeck so we'd actually get to mir const checks

rust-bors · 2025-11-27T10:41:54Z

☀️ Try build successful (CI)
Build commit: 1a2d233 (1a2d2335c5ae8430107aa12ba73195c9b8aca1f0, parent: a4175159da185130408f71d7aa7e9bff0d455c24)

rust-timer · 2025-11-27T12:00:39Z

Finished benchmarking commit (1a2d233): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.1%	[0.1%, 0.2%]	12
Regressions ❌ (secondary)	0.2%	[0.0%, 0.3%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[0.1%, 0.2%]	12

Max RSS (memory usage)

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

Cycles

Results (primary -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)	-2.7%	[-3.0%, -2.3%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.7%	[-3.0%, -2.3%]	2

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%	[0.1%, 0.1%]	4
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	34
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[0.1%, 0.1%]	4

Bootstrap: 472.621s -> 472.008s (-0.13%)
Artifact size: 386.88 MiB -> 386.98 MiB (0.03%)

fee1-dead · 2025-11-28T17:43:05Z

there are performance regressions, are you planning on addressing them?

bors · 2025-11-30T18:23:51Z

☔ The latest upstream changes (presumably #149478) made this pull request unmergeable. Please resolve the merge conflicts.

oli-obk · 2025-12-04T08:36:59Z

@bors try jobs=dist-arm-linux-gnueabi

rust-bors · 2025-12-04T08:37:02Z

🔒 Merge conflict

This pull request and the base branch diverged in a way that cannot
be automatically merged. Please rebase on top of the latest base
branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository,
you can resolve the conflict following these steps:

git checkout const_typeck (switch to your branch)
git fetch upstream HEAD (retrieve the latest base branch)
git rebase upstream/HEAD -p (rebase on top of it)
Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
git push self const_typeck --force-with-lease (update this PR)

You may also read
Git Rebasing to Resolve Conflicts by Drew Blessing
for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub.
It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is
handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

oli-obk · 2025-12-04T08:37:33Z

@bors try jobs=dist-arm-linux-gnueabi

Perform many const checks in typeck try-job: dist-arm-linux-gnueabi

rust-bors · 2025-12-04T10:12:48Z

☀️ Try build successful (CI)
Build commit: 7dd1e55 (7dd1e55361257601fd3b33f5f51b5cc36e1fc724, parent: 556beb9ec72360512d0294eb0855c92fb2c20c88)

oli-obk · 2025-12-09T16:44:50Z

@bors try jobs=dist-aarch64-linux

Perform many const checks in typeck try-job: dist-aarch64-linux

rust-bors · 2025-12-09T19:01:14Z

☀️ Try build successful (CI)
Build commit: 7bee76c (7bee76cb46d2db3f0598ce7421f5d5b65c87ae55, parent: e2893f7c95e45f74c8bc5dbd033486c5bfaa4deb)

rustbot · 2026-02-06T19:39:12Z

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.

oli-obk · 2026-02-06T19:39:24Z

@bors try @rust-timer queue

Perform many const checks in typeck

rust-bors · 2026-02-06T21:50:36Z

☀️ Try build successful (CI)
Build commit: 8df7551 (8df75519ebaa5bab34b38dcac69345e4ce3d02ce, parent: bce89b6a56fecd6f1a150c9657e4b50dea994f83)

rust-timer · 2026-02-06T22:32:01Z

Finished benchmarking commit (8df7551): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	3

Max RSS (memory usage)

Results (primary -0.7%, secondary 6.0%)

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)	6.0%	[6.0%, 6.0%]	1
Improvements ✅ (primary)	-0.7%	[-0.9%, -0.5%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.7%	[-0.9%, -0.5%]	2

Cycles

Results (secondary -1.9%)

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)	2.6%	[2.6%, 2.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-6.4%	[-6.4%, -6.4%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 474.508s -> 475.606s (0.23%)
Artifact size: 397.96 MiB -> 398.04 MiB (0.02%)

oli-obk · 2026-02-07T07:13:40Z

@rustbot ready

The first perf run must have been a fluke. It doesn't reproduce and all my local debugging never pointed me to anything reasonable

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 Nov 27, 2025

rustbot assigned fee1-dead Nov 27, 2025