Error on projection of dyn noncompat type in old trait solver by spirali · Pull Request #154992 · rust-lang/rust

spirali · 2026-04-08T15:18:39Z

Trying to fixrust-lang/trait-system-refactor-initiative#269

I am not sure that the check is placed into the right place in the code.

r? lcnr

lcnr · 2026-04-09T08:21:11Z

 //~^ ERROR the trait `Foo` is not dyn compatible
 x.method();
- //~^ ERROR the trait `Foo` is not dyn compatible
+ //~^ ERROR no method named `method` found for reference `&dyn Foo`


View changes since the review
that's annoying :< ideally we'd silence method errors if the self type is not well-formed, tracking that is non-trivial and I don't know how we'd do so myself rn

lcnr · 2026-04-09T08:21:29Z

lgtm, let's do a crater run, there should be exactly 1 regression from this

@bors try

Error on projection of dyn noncompat type in old trait solver

rust-bors · 2026-04-09T10:29:55Z

☀️ Try build successful (CI)
Build commit: a611f2a (a611f2a14e38407ec6717a86a01424ee6fc80762, parent: 1fe72d35998dea48aeecaf7fc07783b0b553f24f)

lcnr · 2026-04-09T11:12:28Z

@craterbot check

craterbot · 2026-04-09T11:12:52Z

👌 Experiment pr-154992 created and queued.
🤖 Automatically detected try build a611f2a
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-04-20T21:36:22Z

🚧 Experiment pr-154992 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-04-22T22:22:36Z

🎉 Experiment pr-154992 is completed!
📊 18 regressed and 6 fixed (886019 total)
📊 5676 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-154992/retry-regressed-list.txt↩

lcnr · 2026-04-27T08:11:02Z

@craterbot check crates=https://crater-reports.s3.amazonaws.com/pr-154992/retry-regressed-list.txt

craterbot · 2026-04-27T08:11:11Z

👌 Experiment pr-154992-1 created and queued.
🤖 Automatically detected try build a611f2a
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

lcnr · 2026-04-27T08:11:19Z

@craterbot p=1

craterbot · 2026-04-27T08:11:21Z

📝 Configuration of the pr-154992-1 experiment changed.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-04-27T12:04:56Z

🚧 Experiment pr-154992-1 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-04-27T17:19:44Z

🎉 Experiment pr-154992-1 is completed!
📊 13 regressed and 0 fixed (5381 total)
📊 968 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-154992-1/retry-regressed-list.txt↩

lcnr · 2026-04-29T08:19:48Z

@craterbot check crates=https://crater-reports.s3.amazonaws.com/pr-154992-1/retry-regressed-list.txt p=1

surprising that we have that many spurious regressions still?

it's caused by build OOMs and unlike the new solver, this PR shouldn't really change max-rss in any way 😅 cc @rust-lang/infra

craterbot · 2026-04-29T08:19:54Z

👌 Experiment pr-154992-2 created and queued.
🤖 Automatically detected try build a611f2a
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

rust-rfcbot · 2026-08-16T20:33:35Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

lcnr · 2026-08-17T09:27:54Z

+ let tcx = selcx.tcx();
+ if !tcx.is_dyn_compatible(def_id) {
+ let span = obligation.cause.span;
+ let guar = if span.is_dummy()


comment why we can delay bug here
I guess it's that this should be handled in WF instead?
View changes since the review

Comment added

lcnr

final nit, then r=me

View changes since this review

Kobzol · 2026-08-17T09:29:22Z

@bors delegate

rust-bors · 2026-08-17T09:29:25Z

✌️ @spirali, you can now approve this pull request!

If @Kobzol told you to "r=me" after making some further change, then please make that change and post @bors r=Kobzol.

View changes since this delegation.

spirali · 2026-08-22T07:16:17Z

@bors r=lcnr

rust-bors · 2026-08-22T07:16:19Z

📌 Commit e2fcf35 has been approved by lcnr

It is now in the queue for this repository.

Error on projection of dyn noncompat type in old trait solver Trying to fixrust-lang/trait-system-refactor-initiative#269 I am not sure that the check is placed into the right place in the code. r? lcnr

…uwer Rollup of 19 pull requests Successful merges: - #151061 (Build rustc and codegen backends with -Zembed-metadata=no) - #154992 (Error on projection of dyn noncompat type in old trait solver) - #157949 (Allow self in const generics) - #158588 (trait_selection: fix assumptions-on-binders diagnostics) - #159954 (core: implement float conversion methods) - #160136 (Add `Default` implementation for `std::sync::Once`) - #160835 (resolver diagnostics: don't swallow labels and point out similar items as a note, not a label) - #161048 (Improve the ABI between the panic runtime and libstd) - #161292 (Add safety comments in alloc::Wtf8) - #161444 (Add some `rustc_type_ir` comments) - #161465 (Remove leftover immediate creation) - #159098 (Add Arc/Rc::strong_count_from_raw) - #159282 (Update documentation for `-Zdump-dep-graph`) - #161401 (Remove fields from TypeKind: Bool, Char, Float and Int) - #161431 (bootstrap: (offload) be stricter about selected compiler and paths) - #161451 (Avoid arming the Windows TLS destructor guard in fibers) - #161463 (Add myself to mailmap) - #161476 (Use bitset for locals_with_use_data) - #161483 (Warn about running ui-fulldeps tests in stage 1) Failed merges: - #161443 (add internal DSL for testing binders)

Rollup merge of #154992 - spirali:fix-dyn-projection, r=lcnr Error on projection of dyn noncompat type in old trait solver Trying to fixrust-lang/trait-system-refactor-initiative#269 I am not sure that the check is placed into the right place in the code. r? lcnr

dimpolo · 2026-08-23T02:28:51Z

I noticed some breakage in todays nightly #161536 and my LLM pointed me at this issue

…uwer Rollup of 19 pull requests Successful merges: - rust-lang/rust#151061 (Build rustc and codegen backends with -Zembed-metadata=no) - rust-lang/rust#154992 (Error on projection of dyn noncompat type in old trait solver) - rust-lang/rust#157949 (Allow self in const generics) - rust-lang/rust#158588 (trait_selection: fix assumptions-on-binders diagnostics) - rust-lang/rust#159954 (core: implement float conversion methods) - rust-lang/rust#160136 (Add `Default` implementation for `std::sync::Once`) - rust-lang/rust#160835 (resolver diagnostics: don't swallow labels and point out similar items as a note, not a label) - rust-lang/rust#161048 (Improve the ABI between the panic runtime and libstd) - rust-lang/rust#161292 (Add safety comments in alloc::Wtf8) - rust-lang/rust#161444 (Add some `rustc_type_ir` comments) - rust-lang/rust#161465 (Remove leftover immediate creation) - rust-lang/rust#159098 (Add Arc/Rc::strong_count_from_raw) - rust-lang/rust#159282 (Update documentation for `-Zdump-dep-graph`) - rust-lang/rust#161401 (Remove fields from TypeKind: Bool, Char, Float and Int) - rust-lang/rust#161431 (bootstrap: (offload) be stricter about selected compiler and paths) - rust-lang/rust#161451 (Avoid arming the Windows TLS destructor guard in fibers) - rust-lang/rust#161463 (Add myself to mailmap) - rust-lang/rust#161476 (Use bitset for locals_with_use_data) - rust-lang/rust#161483 (Warn about running ui-fulldeps tests in stage 1) Failed merges: - rust-lang/rust#161443 (add internal DSL for testing binders)

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 8, 2026

rustbot assigned lcnr Apr 8, 2026

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Apr 8, 2026

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rust-borsBot pushed a commit that referenced this pull request Apr 9, 2026
Auto merge of#154992- spirali:fix-dyn-projection, r=<try>
a611f2a
Error on projection of dyn noncompat type in old trait solver

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 9, 2026

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Apr 22, 2026

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 27, 2026

craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Apr 27, 2026

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 29, 2026

rust-rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Aug 16, 2026

rust-rfcbot added the to-announce Announce this issue on triage meeting label Aug 16, 2026

rustbot mentioned this pull request Aug 16, 2026
Tracking issue for release notes of #154992: Error on projection of dyn noncompat type in old trait solver #161194
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lcnr reviewed Aug 17, 2026
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e2fcf35

rust-borsBot 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 22, 2026

jhpratt mentioned this pull request Aug 22, 2026
Rollup of 19 pull requests #161497
Closed

JonathanBrouwer mentioned this pull request Aug 22, 2026
Rollup of 18 pull requests #161498
Closed

This was referenced Aug 22, 2026
Rollup of 18 pull requests #161501
Closed
Rollup of 19 pull requests #161505
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rust-borsBot merged commit 9c98028 into rust-lang:mainAug 22, 2026
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rustbot added this to the 1.100.0 milestone Aug 22, 2026

dimpolo mentioned this pull request Aug 23, 2026
cycle detected when checking if trait is dyn-compatible with next-gen trait solver and arbitrary_self_types#161536
Open

This was referenced Aug 27, 2026
stabilize -Znext-solver=coherence again #130654
Merged
Stabilize the next-generation trait solver rust-lang/goals#113
Open

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