Remove the witness type from coroutine args (without actually removing the type)#144458

compiler-errors · 2025-07-25T16:54:02Z

This does as much of #144157 as we can without having to break #143545 and/or introduce some better way of handling higher ranked assumptions.

Namely, it:

Stalls coroutines based off of the coroutine type rather than the witness type.
Reworks the dtorck constraint hack to not rely on the witness type.
Removes the witness type from the args of the coroutine, eagerly creating the type for nested obligations when needed (auto/clone impls).

I'll experiment with actually removing the witness type in a follow-up.

r? lcnr

rustbot · 2025-07-25T16:54:08Z

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

lcnr · 2025-07-28T06:55:31Z

compiler/rustc_ty_utils/src/needs_drop.rs

-                        if self.reveal_coroutine_witnesses {
-                            queue_type(self, args.as_coroutine().witness());
+                    ty::Coroutine(def_id, args) => {
+                        if self.exhaustive {


please add the FIXME to exhaustive again

lcnr · 2025-07-31T13:21:07Z

r=me after nit

compiler-errors · 2025-07-31T17:45:27Z

@bors r=lcnr rollup=never

bors · 2025-07-31T17:45:30Z

📌 Commit e976578 has been approved by lcnr

It is now in the queue for this repository.

Remove the witness type from coroutine *args* (without actually removing the type) This does as much of #144157 as we can without having to break #143545 and/or introduce some better way of handling higher ranked assumptions. Namely, it: * Stalls coroutines based off of the *coroutine* type rather than the witness type. * Reworks the dtorck constraint hack to not rely on the witness type. * Removes the witness type from the args of the coroutine, eagerly creating the type for nested obligations when needed (auto/clone impls). I'll experiment with actually removing the witness type in a follow-up. r? lcnr

bors · 2025-07-31T19:48:59Z

⌛ Testing commit e976578 with merge cdc9f26...

bors · 2025-08-01T01:48:59Z

💥 Test timed out

rust-log-analyzer · 2025-08-01T01:54:47Z

A job failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

lcnr · 2025-08-01T07:49:14Z

@bors retry

bors · 2025-08-01T21:07:52Z

⌛ Testing commit e976578 with merge 63f6845...

bors · 2025-08-02T00:27:45Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 63f6845 to master...

github-actions · 2025-08-02T00:30:25Z

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 4b55fe1 (parent) -> 63f6845 (this PR)

Test differences

Show 18 test diffs

18 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 63f6845e570305a92eaf855897768617366164d6 --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

x86_64-apple-1: 6309.5s -> 8161.5s (29.4%)
pr-check-2: 2287.1s -> 2791.0s (22.0%)
x86_64-apple-2: 5016.9s -> 6088.8s (21.4%)
dist-aarch64-apple: 8140.6s -> 6451.2s (-20.8%)
x86_64-rust-for-linux: 2523.5s -> 2966.4s (17.5%)
pr-check-1: 1507.7s -> 1760.3s (16.7%)
x86_64-gnu-llvm-19: 2539.5s -> 2929.1s (15.3%)
aarch64-gnu-debug: 3676.2s -> 4217.3s (14.7%)
aarch64-gnu-llvm-19-2: 2254.0s -> 2578.4s (14.4%)
x86_64-gnu-tools: 3314.5s -> 3728.6s (12.5%)

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-timer · 2025-08-02T01:38:22Z

Finished benchmarking commit (63f6845): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

If the regression was expected or you think it can be justified,
please write a comment with sufficient written justification, and add
@rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
If you think that you know of a way to resolve the regression, try to create
a new PR with a fix for the regression.
If you do not understand the regression or you think that it is just noise,
you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

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)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-1.5%	[-1.5%, -1.5%]	1
Improvements ✅ (secondary)	-0.5%	[-1.5%, -0.0%]	5
All ❌✅ (primary)	-1.5%	[-1.5%, -1.5%]	1

Max RSS (memory usage)

Results (primary 2.2%)

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

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.2%	[2.2%, 2.2%]	1

Cycles

Results (primary 2.8%, 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)	2.8%	[2.8%, 2.8%]	1
Regressions ❌ (secondary)	2.9%	[2.9%, 2.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[2.8%, 2.8%]	1

Binary size

Results (primary -0.0%, 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)	-	-	0
Improvements ✅ (primary)	-0.0%	[-0.0%, -0.0%]	4
Improvements ✅ (secondary)	-0.3%	[-0.7%, -0.0%]	13
All ❌✅ (primary)	-0.0%	[-0.0%, -0.0%]	4

Bootstrap: 467.125s -> 468.385s (0.27%)
Artifact size: 376.83 MiB -> 376.83 MiB (-0.00%)

panstromek · 2025-08-04T13:47:41Z

perf triage:

include-blobs looks like noise, just returned to previous state.

@rustbot label: +perf-regression-triaged

Remove the witness type from coroutine *args* (without actually removing the type) This does as much of rust-lang#144157 as we can without having to break rust-lang#143545 and/or introduce some better way of handling higher ranked assumptions. Namely, it: * Stalls coroutines based off of the *coroutine* type rather than the witness type. * Reworks the dtorck constraint hack to not rely on the witness type. * Removes the witness type from the args of the coroutine, eagerly creating the type for nested obligations when needed (auto/clone impls). I'll experiment with actually removing the witness type in a follow-up. r? lcnr

rustbot assigned lcnr Jul 25, 2025

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. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Jul 25, 2025

compiler-errors force-pushed the no-witness-mini branch from 2bf9c66 to 7209b8e Compare July 25, 2025 16:55

compiler-errors mentioned this pull request Jul 25, 2025

Remove the CoroutineWitness type #144157

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compiler-errors force-pushed the no-witness-mini branch from 7209b8e to 8756bdc Compare July 25, 2025 17:47

lcnr reviewed Jul 28, 2025

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lcnr 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 Jul 31, 2025

compiler-errors added 3 commits July 31, 2025 17:31

Stall coroutines based off of ty::Coroutine, not ty::CoroutineWitness

d525e79

Extract borrowck coroutine drop-liveness hack

d05bb98

Remove the witness type from coroutine args

e976578

compiler-errors force-pushed the no-witness-mini branch from 8756bdc to e976578 Compare July 31, 2025 17:38

bors 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 Jul 31, 2025

bors 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 Aug 1, 2025

bors 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 Aug 1, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 2, 2025

bors merged commit 63f6845 into rust-lang:master Aug 2, 2025
11 checks passed

rustbot added this to the 1.90.0 milestone Aug 2, 2025

This was referenced Aug 2, 2025

Check coroutine upvars in dtorck constraint #144156

Merged

[WIP] Check coroutine upvars and resume ty in dtorck constraint, this time based off of TypingMode #144158

Closed

rustbot added the perf-regression Performance regression. label Aug 2, 2025

bors mentioned this pull request Aug 2, 2025

Printer cleanups #144776

Merged

rustbot added the perf-regression-triaged The performance regression has been triaged. label Aug 4, 2025

theemathas mentioned this pull request Aug 9, 2025

E0275 is occuring in beta 1.90.0-beta.1 but not in stable 1.89.0 #145151

Closed

compiler-errors mentioned this pull request Aug 10, 2025

Revert "Remove the witness type from coroutine args" #145193

Closed

matthiaskrgr mentioned this pull request Sep 4, 2025

ICE: Unsize coercion, but std::pin::Pin<std::boxed::Box<{async block .. isn't coercible #146210

Open

Noratrieb mentioned this pull request Oct 17, 2025

Unstable fingerprints in evaluate_obligation #147825

Closed

matthiaskrgr mentioned this pull request Nov 4, 2025

ICE Unexpected unnameable type in variance computation #148488

Closed

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Test differences

Job duration changes

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rust-timer commented Aug 2, 2025

Overall result: ❌✅ regressions and improvements - please read the text below

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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panstromek commented Aug 4, 2025

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