stricter hidden type wf-check #115008

aliemjay · 2023-08-19T20:50:51Z

Combines #114740 and #114933 for a shared crater run, fixes #114728

#114740 should handle all the cases we unintentionally miss in #114933 and I expect #114933 to fix most of the crater regressions of #114740.

However this is still a regression:

trait Id<X> { type Ty; }
impl<X> Id<X> for () { type Ty = X; }
fn test<T>() -> impl Id<&'static T, Ty = impl Sized> {}

We should probably ignore the wf-check nested RPIT, similar to nested TAIT.

r? @ghost
cc @compiler-errors

rustbot · 2023-08-19T20:50:55Z

Some changes occurred to the core trait solver

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

aliemjay · 2023-08-19T20:51:49Z

@bors try

bors · 2023-08-19T20:51:59Z

⌛ Trying commit ca0634b with merge e7920004d5fc5c25e6a81a373abcc9e5161ff603...

bors · 2023-08-19T22:04:13Z

☀️ Try build successful - checks-actions
Build commit: e7920004d5fc5c25e6a81a373abcc9e5161ff603 (e7920004d5fc5c25e6a81a373abcc9e5161ff603)

aliemjay · 2023-08-19T22:39:05Z

(p=1 because it's only a small list)
@craterbot check p=1 crates=https://crater-reports.s3.amazonaws.com/pr-114740/retry-regressed-list.txt

craterbot · 2023-08-19T22:39:10Z

👌 Experiment pr-115008 created and queued.
🤖 Automatically detected try build e7920004d5fc5c25e6a81a373abcc9e5161ff603
🔍 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 · 2023-08-20T02:15:33Z

🚧 Experiment pr-115008 is now running

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

craterbot · 2023-08-20T02:36:18Z

🎉 Experiment pr-115008 is completed!
📊 6 regressed and 0 fixed (298 total)
📰 Open the full report.

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

The soundness fix in rust-lang/rust#115008 will cause axum-starter to break, even though it is not unsound. The missing bound is very hard to abuse, but still a soundness hole in our type system. It will likely take 12 weeks before a stable compiler with the soundness fix is shipped.

The soundness fix in rust-lang/rust#115008 will cause `discord` to break, even though it is not unsound. The missing bound is very hard to abuse, but still a soundness hole in our type system. It will likely take 12 weeks before a stable compiler with the soundness fix is shipped.

The soundness fix in rust-lang/rust#115008 will cause schemat to break, even though it is not unsound. The missing bound is very hard to abuse, but still a soundness hole in our type system. It will likely take 12 weeks before a stable compiler with the soundness fix is shipped.

The soundness fix in rust-lang/rust#115008 will cause `discord` to break, even though it is not unsound. The missing bound is very hard to abuse, but still a soundness hole in our type system. It will likely take 12 weeks before a stable compiler with the soundness fix is shipped.

oli-obk · 2023-10-11T14:07:53Z

This PR fixes a soundness hole, where we were failing to check that hidden types are actually well formed wrt to lifetimes. From a not-well formed hidden type you can easily satisfy trait bounds that make no sense and thus allow treating any lifetime as another lifetime that lives longer.

The implementation adds well-formedness predicates, which should always be sound and at worst a performance issue (#114933 does the same thing). In addition, during wf check of RPIT and async fn return types we do region checking of these opaques within their owning function, catching the remaining soundness bugs (which is what #114740 does).

I do not believe there is any possible risk with this PR, beyond causing breakage for benign code that just forgot some bounds somewhere. Crater showed 3 such cases, which all have PRs opened, with only one not having been noticed by the crate owners yet.

@rfcbot fcp merge

rfcbot · 2023-10-11T14:07:55Z

Team member @oli-obk has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

lcnr · 2023-10-13T09:57:00Z

tests/ui/traits/new-solver/auto-with-drop_tracking_mir.rs

+//[pass] check-fail
+// WARN new-solver BUG.


please instead check this to known-bug or FIXME(-Ztrait-solver=next)

rfcbot · 2023-10-30T02:42:39Z

🔔 This is now entering its final comment period, as per the review above. 🔔

rfcbot · 2023-11-09T02:42:44Z

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.

This will be merged soon.

stricter hidden type wf-check [based on rust-lang#115008] Original work by `@aliemjay` in rust-lang#115008. A huge thanks to them for originally figuring out this approach ❤️ Fixes rust-lang#114728 Fixes rust-lang#114572 Instead of adding the `WellFormed` obligations when relating opaque types, I add always emit such an obligation when defining the hidden type. This causes nested opaque types which aren't wf to error, see the comment below for the described impact. I believe this change to be desirable as it significantly reduces complexity by removing special-cases. It also caused an issue with RPITIT: in defaulted trait methods, we add a `Projection(synthetic_assoc, rpit_of_trait_method)` clause to the `param_env`. This clause is not added to the `ParamEnv` of the nested coroutines. This caused a normalization failure in `fn check_coroutine_obligations` with the new solver. I fixed that by using the env of the typeck root instead. r? `@oli-obk`

lcnr · 2024-03-07T10:46:00Z

I force pushed to aliemjays repo as well by accident? 😅 alright, have to be more careful next time 😅

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 labels Aug 19, 2023

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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 Aug 20, 2023

lcnr mentioned this pull request Sep 7, 2023

wf-check hidden types at definition site #114933

Closed

oli-obk mentioned this pull request Sep 21, 2023

Prepare for a breaking change in the Rust compiler. Goodjooy/axum-server-starter#51

Closed

oli-obk mentioned this pull request Sep 21, 2023

Prepare for a breaking change in the Rust compiler. project-chip/rs-matter#98

Closed

oli-obk mentioned this pull request Sep 21, 2023

Prepare for a breaking change in the Rust compiler. raviqqe/schemat#56

Merged

oli-obk mentioned this pull request Sep 21, 2023

Prepare for a breaking change in the Rust compiler. Astavie/CardMaster#3

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oli-obk mentioned this pull request Sep 21, 2023

Prepare for a breaking change in the Rust compiler. rorm-orm/rorm-sql#1

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rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Oct 11, 2023

lcnr reviewed Oct 13, 2023

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rfcbot added the final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. label Oct 30, 2023

rfcbot removed the proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. label Oct 30, 2023

rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. to-announce Announce this issue on triage meeting and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Nov 9, 2023

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lcnr added 2 commits February 27, 2024 15:00

wf-check RPITs

93bc7a4

when defining opaques, require the hidden type to be well-formed

71d82c2

lcnr mentioned this pull request Feb 27, 2024

stricter hidden type wf-check [based on #115008] #121679

Merged

lcnr added 3 commits February 27, 2024 17:13

use typeck root when checking closure oblig

6591c80

yeet now unnecessary special-case

300cffa

update comments

af0d508

lcnr force-pushed the opaque-wf-check-2 branch from ca0634b to af0d508 Compare February 27, 2024 17:41

bors merged commit 09bc67b into rust-lang:master Mar 6, 2024
23 checks passed

rustbot added this to the 1.78.0 milestone Mar 6, 2024

oli-obk mentioned this pull request Mar 10, 2024

Lifetime may not live enough regression #122230

Closed

traviscross mentioned this pull request Mar 19, 2024

Stabilize associated type position impl Trait (ATPIT) #120700

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3 tasks

compiler-errors mentioned this pull request Apr 1, 2024

regression: parameter type may not live long enough #123280

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stricter hidden type wf-check #115008

stricter hidden type wf-check #115008

aliemjay commented Aug 19, 2023 •

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stricter hidden type wf-check #115008

stricter hidden type wf-check #115008

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