privacy: Fix type privacy holes in RPITITs by petrochenkov · Pull Request #152543 · rust-lang/rust

petrochenkov · 2026-02-12T15:36:53Z

A subset of #146470.

Private types in RPITITs now report hard errors.
Private types in bounds of associated types still only report the private_bounds lint due to unacceptable amount of breakage (#146470 (comment)).

Closes #144139

petrochenkov · 2026-02-12T15:37:12Z

@bors try

privacy: Fix type privacy holes when it doesn't cause too much breakage

petrochenkov · 2026-02-12T15:38:01Z

TODO: @craterbot check p=1 crates=https://crater-reports.s3.amazonaws.com/pr-146470-3/retry-regressed-list.txt

rustbot · 2026-02-12T15:38:12Z

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rust-bors · 2026-02-12T17:49:21Z

☀️ Try build successful (CI)
Build commit: fcfb0ff (fcfb0ffc7ed7fc631df1136063939ef648434735, parent: 7ad4e69ad585d8ff214f7b42d01f1959eda08f40)

petrochenkov · 2026-02-12T17:58:45Z

@craterbot check p=1 crates=https://crater-reports.s3.amazonaws.com/pr-146470-3/retry-regressed-list.txt

craterbot · 2026-02-12T17:58:49Z

👌 Experiment pr-152543 created and queued.
🤖 Automatically detected try build fcfb0ff
🔍 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 · 2026-02-12T17:59:43Z

🚧 Experiment pr-152543 is now running

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

craterbot · 2026-02-12T20:35:45Z

🎉 Experiment pr-152543 is completed!
📊 27 regressed and 0 fixed (5514 total)
📊 267 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-152543/retry-regressed-list.txt ↩

petrochenkov · 2026-02-13T12:12:43Z

Crater results are basically the same as #146470 without the second commit (see e.g. #146470 (comment)).

petrochenkov · 2026-02-13T12:14:52Z

Previous FCP - #146470 (comment).

rust-rfcbot · 2026-03-11T05:52:07Z

Team member @traviscross 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!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

scottmcm · 2026-03-11T15:48:03Z

Making RPITIT match the RPIT behaviour makes sense to me.

(TBH it's not obvious to me that private bounds on an associated type are even a "problem" that we'd need to fix, but now that this isn't changing that, sure, happy to make it consistent in function return position. Especially if the public trait is sealed, having various non-public bounds on things doesn't seem unreasonable.)

@rfcbot reviewed

tmandry · 2026-03-11T15:49:07Z

Agreed with @scottmcm. I'm happy to make things more consistent and save space for another model in the future. Not sure we'll need this restriction in the long run.

@rfcbot reviewed

rust-rfcbot · 2026-03-11T15:49:20Z

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

nikomatsakis · 2026-03-11T15:49:27Z

Soooooo I still feel like I am missing a mental model for what we are attempting to achieve with our rules around privacy and private traits. It makes all of these changes feel kind of random to me. That said, I think we previously decided to move forward here, and this seems consistent with that, and RPITIT/RPIT consistency is good, and it seems like this will give us room to make more decisions in the future, so....

@rfcbot reviewed

rust-rfcbot · 2026-03-21T16:00:21Z

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.

fmease

This PR leads to quite a few breakages but it seems too tricky and arduous to send downstream patches, unfortunately. @bors r+

View changes since this review

rust-bors · 2026-03-22T16:24:18Z

📌 Commit ef8c95c has been approved by fmease

It is now in the queue for this repository.

privacy: Fix type privacy holes in RPITITs A subset of rust-lang#146470. Private types in RPITITs now report hard errors. Private types in bounds of associated types still only report the `private_bounds` lint due to unacceptable amount of breakage (rust-lang#146470 (comment)). Closes rust-lang#144139

…uwer Rollup of 22 pull requests Successful merges: - #122668 (Add APIs for dealing with titlecase) - #152543 (privacy: Fix type privacy holes in RPITITs) - #153107 (Optimize BTreeMap::append() using CursorMut) - #153312 (Packages as namespaces part 1) - #153534 (Remove a flaky `got_timeout` assert from two channel tests) - #153718 (Fix environ on FreeBSD with cdylib targets that use -Wl,--no-undefined .) - #153857 (Rename `target.abi` to `target.cfg_abi` and enum-ify llvm_abiname) - #153880 (Lifted intersperse and intersperse_with Fused transformation and updated documentation + tests) - #153931 (remove usages of to-be-deprecated numeric constants) - #150630 (Unknown -> Unsupported compression algorithm) - #153491 (Move `freeze_*` methods to `OpenOptionsExt2`) - #153582 (Simplify find_attr! for HirId usage) - #153623 (std: move `sys::pal::os` to `sys::paths`) - #153647 (docs(fs): Clarify That File::lock Coordinates Across Processes) - #153936 (Skip stack_start_aligned for immediate-abort) - #154011 (implement `BinaryHeap::as_mut_slice`) - #154167 (ui/lto: move and rename two tests from issues/) - #154174 (allow `incomplete_features` in most UI tests) - #154175 (Add new alias for Guillaume Gomez email address) - #154182 (diagnostics: avoid ICE for undeclared generic parameter in impl) - #154188 (Update the tracking issue for #[diagnostic::on_move]) - #154201 (Use enums to clarify `DepNodeColorMap` color marking )

privacy: Fix type privacy holes when it doesn't cause too much breakage

ef8c95c

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Feb 12, 2026

rust-bors bot pushed a commit that referenced this pull request Feb 12, 2026

Auto merge of #152543 - petrochenkov:rprivtit2, r=<try>

fcfb0ff

privacy: Fix type privacy holes when it doesn't cause too much breakage

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petrochenkov marked this pull request as ready for review February 12, 2026 15:38

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This was referenced Feb 12, 2026

Revert "Do not check privacy for RPITIT." #146470

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(re-)Fix private-in-public for RPITIT #144139

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rustbot mentioned this pull request Mar 21, 2026

Tracking issue for release notes of #152543: privacy: Fix type privacy holes in RPITITs #154180

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fmease added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-t-lang Status: Awaiting decision from T-lang labels Mar 22, 2026

fmease changed the title ~~privacy: Fix type privacy holes when it doesn't cause too much breakage~~ privacy: Fix type privacy holes in RPITITs Mar 22, 2026

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JonathanBrouwer mentioned this pull request Mar 22, 2026

Rollup of 13 pull requests #154219

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JonathanBrouwer mentioned this pull request Mar 22, 2026

Rollup of 23 pull requests #154226

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JonathanBrouwer mentioned this pull request Mar 22, 2026

Rollup of 22 pull requests #154227

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