Deny-by-default never type lints #146167

WaffleLapkin · 2025-09-03T17:04:33Z

In Rust 1.89.0 we started emitting these lints in dependencies. I discussed the future steps with @lcnr and we think that before stabilizing the never type (and doing the breaking changes) we should deny the lints for ~4 releases.

This PR marks never_type_fallback_flowing_into_unsafe and dependency_on_unit_never_type_fallback lints as deny-by-default.

Tracking:

Tracking issue for promoting ! to a type (RFC 1216) #35121

Report never type lints in dependencies #141937

rustbot · 2025-09-03T17:04:38Z

r? @petrochenkov

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WaffleLapkin · 2025-09-03T17:06:48Z

@bors try

Deny-by-default never type lints

WaffleLapkin · 2025-09-03T17:11:52Z

T-lang nomination

This PR marks never_type_fallback_flowing_into_unsafe and dependency_on_unit_never_type_fallback lints as deny-by-default. I think this is the next step towards never type stabilization.

rust-bors · 2025-09-03T19:28:28Z

☀️ Try build successful (CI)
Build commit: e90f1ff (e90f1ff63e694965281f833819a486da29772bdf, parent: 51ff895062ba60a7cba53f57af928c3fb7b0f2f4)

WaffleLapkin · 2025-09-04T10:55:14Z

@craterbot check

craterbot · 2025-09-04T10:55:42Z

👌 Experiment pr-146167 created and queued.
🤖 Automatically detected try build e90f1ff
🔍 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 · 2025-09-07T07:03:33Z

🚧 Experiment pr-146167 is now running

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

lcnr · 2025-09-08T09:16:25Z

I discussed the future steps with @lcnr and we think that before stabilizing the never type (and doing the breaking changes) we should deny the lints for ~4 releases.

I personally would convert the lint to a hard error for a few versions :> Users can still ignore denied lints (e.g. if it's in a dependency)

craterbot · 2025-09-08T21:32:16Z

🎉 Experiment pr-146167 is completed!
📊 474 regressed and 3 fixed (693868 total)
📊 1781 spurious results on the retry-regessed-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-146167/retry-regressed-list.txt ↩

…r=lcnr,petrochenkov Deny-by-default never type lints In Rust [1.89.0](https://github.com/rust-lang/rust/milestone/133) we started emitting these lints in dependencies. I discussed the future steps with `@lcnr` and we think that before stabilizing the never type (and doing the breaking changes) we should deny the lints for ~4 releases. This PR marks `never_type_fallback_flowing_into_unsafe` and `dependency_on_unit_never_type_fallback` lints as deny-by-default. Tracking: - rust-lang#35121 Related: - rust-lang#141937

Rollup of 8 pull requests Successful merges: - #138679 (Issue-125323: ICE non-ADT in struct pattern when long time constant evaluation is in for loop) - #146167 (Deny-by-default never type lints) - #146490 (Rehome 26 `tests/ui/issues/` tests to other subdirectories under `tests/ui/` [#5 of Batch #2]) - #147438 (Rename "non-inline module" to "file module" in proc macro diagnostics) - #147724 (Fix ICE in pattern matching with generic const array length errors) - #147813 (Warn on unused_attributes in uitests ) - #147816 (Do not error out for `download-rustc` if LTO is configured) - #147845 (Add regression test for 134355) r? `@ghost` `@rustbot` modify labels: rollup

matthiaskrgr · 2025-10-18T21:53:31Z

@bors r-
https://github.com/rust-lang/rust/pull/147856#issuecomment-3418858812https://github.com/rust-lang/rust/pull/147856#issuecomment-3418858812

WaffleLapkin · 2025-10-19T22:39:53Z

@bors r=lcnr,petrochenkov

bors · 2025-10-19T22:39:55Z

📌 Commit 08b4323 has been approved by lcnr,petrochenkov

It is now in the queue for this repository.

…r=lcnr,petrochenkov Deny-by-default never type lints In Rust [1.89.0](https://github.com/rust-lang/rust/milestone/133) we started emitting these lints in dependencies. I discussed the future steps with `@lcnr` and we think that before stabilizing the never type (and doing the breaking changes) we should deny the lints for ~4 releases. This PR marks `never_type_fallback_flowing_into_unsafe` and `dependency_on_unit_never_type_fallback` lints as deny-by-default. Tracking: - rust-lang#35121 Related: - rust-lang#141937

Rollup of 2 pull requests Successful merges: - #146167 (Deny-by-default never type lints) - #147382 (unused_must_use: Don't warn on `Result<(), Uninhabited>` or `ControlFlow<Uninhabited, ()>`) r? `@ghost` `@rustbot` modify labels: rollup

bors · 2025-10-20T05:11:48Z

⌛ Testing commit 08b4323 with merge 9f1b801...

…ochenkov Deny-by-default never type lints In Rust [1.89.0](https://github.com/rust-lang/rust/milestone/133) we started emitting these lints in dependencies. I discussed the future steps with `@lcnr` and we think that before stabilizing the never type (and doing the breaking changes) we should deny the lints for ~4 releases. This PR marks `never_type_fallback_flowing_into_unsafe` and `dependency_on_unit_never_type_fallback` lints as deny-by-default. Tracking: - #35121 Related: - #141937

Zalathar · 2025-10-20T05:15:38Z

Yielding to enclosing rollup.

@bors retry

Rollup of 3 pull requests Successful merges: - #146167 (Deny-by-default never type lints) - #147382 (unused_must_use: Don't warn on `Result<(), Uninhabited>` or `ControlFlow<Uninhabited, ()>`) - #147821 (Do not GC the current active incremental session directory) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #146167 - WaffleLapkin:deny-never-ty-lints, r=lcnr,petrochenkov Deny-by-default never type lints In Rust [1.89.0](https://github.com/rust-lang/rust/milestone/133) we started emitting these lints in dependencies. I discussed the future steps with `@lcnr` and we think that before stabilizing the never type (and doing the breaking changes) we should deny the lints for ~4 releases. This PR marks `never_type_fallback_flowing_into_unsafe` and `dependency_on_unit_never_type_fallback` lints as deny-by-default. Tracking: - #35121 Related: - #141937

This adds back the link removed in rust-lang#377 now that rust-lang/rust#146167 has marged.

rustbot assigned petrochenkov Sep 3, 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. labels Sep 3, 2025

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Auto merge of #146167 - WaffleLapkin:deny-never-ty-lints, r=<try>

e90f1ff

Deny-by-default never type lints

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WaffleLapkin mentioned this pull request Sep 4, 2025

link to never type fallback lint as deny by default rust-lang/edition-guide#377

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traviscross added P-lang-drag-1 Lang team prioritization drag level 1. https://rust-lang.zulipchat.com/#narrow/channel/410516-t-lang T-lang Relevant to the language team and removed T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 9, 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 Oct 18, 2025

matthiaskrgr mentioned this pull request Oct 18, 2025

Rollup of 8 pull requests #147856

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bors 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Oct 18, 2025

remove useless #![deny]s

08b4323

WaffleLapkin force-pushed the deny-never-ty-lints branch from 769009a to 08b4323 Compare October 19, 2025 17:57

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 Oct 19, 2025

Zalathar mentioned this pull request Oct 20, 2025

Rollup of 2 pull requests #147897

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Zalathar mentioned this pull request Oct 20, 2025

Rollup of 3 pull requests #147900

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bors merged commit 2a4818d into rust-lang:master Oct 20, 2025
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rustbot added this to the 1.92.0 milestone Oct 20, 2025

ehuss added a commit to ehuss/edition-guide that referenced this pull request Oct 21, 2025

Add back the link for never_type_fallback_flowing_into_unsafe

4914e9d

This adds back the link removed in rust-lang#377 now that rust-lang/rust#146167 has marged.

ehuss mentioned this pull request Oct 21, 2025

Add back the link for never_type_fallback_flowing_into_unsafe rust-lang/edition-guide#378

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WaffleLapkin deleted the deny-never-ty-lints branch October 23, 2025 13:19

cuviper mentioned this pull request Nov 20, 2025

Draft release notes for 1.92 #149161

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apiraino removed the to-announce Announce this issue on triage meeting label Nov 27, 2025

Deny-by-default never type lints #146167

Deny-by-default never type lints #146167

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WaffleLapkin commented Sep 3, 2025 •

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