Report never type lints in dependencies #141937

WaffleLapkin · 2025-06-02T23:50:10Z

This PR marks never type lints (never_type_fallback_flowing_into_unsafe & dependency_on_unit_never_type_fallback) to be included in cargo's reports / to be emitted when they happen in dependencies.

This PR is based on #141936
r? oli-obk

traviscross · 2025-06-03T00:22:31Z

In advance of the Rust 2024 edition, we made a plan for later stabilizing the never type (via FCP in #123508).

The plan went like this:

Change fallback to ! in Rust 2024.
- Tracking Issue for Rust 2024: Make ! fall back to ! #123748
- Add a number of FCWs in all editions against the problematic cases, and make never_type_fallback_flowing_into_unsafe deny-by-default in Rust 2024.
  - See https://doc.rust-lang.org/nightly/edition-guide/rust-2024/never-type-fallback.html.
Stabilize Rust 2024.
At a later date when 2024 edition adoption is widespread:
- Make the breaking change to fall back to ! always everywhere.
- Change Infallible = !.
- Stabilize ! (!).

These FCWs have been out there a long time now -- since Rust 1.80. The edition has been out since Rust 1.85. I propose that we take the next step and extend the FCWs to lint in dependencies in preparation for next taking the final step to change fallback in all editions and stabilize the never type.

@rfcbot fcp merge

Tracking:

rfcbot · 2025-06-03T00:22:34Z

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.

traviscross · 2025-06-03T00:26:15Z

Big thanks to @WaffleLapkin for pushing this forward.

bors · 2025-06-03T14:04:34Z

☔ The latest upstream changes (presumably #141954) made this pull request unmergeable. Please resolve the merge conflicts.

oli-obk

r=me with FCP finished

scottmcm · 2025-06-04T07:59:56Z

Makes sense to me! Always happy to see progress on ! 🙂

@rfcbot reviewed

tmandry · 2025-06-04T15:56:50Z

@rfcbot reviewed

rfcbot · 2025-06-04T15:56:57Z

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

rfcbot · 2025-06-14T15:57:24Z

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.

traviscross · 2025-06-15T05:41:10Z

@bors r=oli-obk,traviscross rollup

bors · 2025-06-15T05:41:12Z

📌 Commit 851129f has been approved by oli-obk,traviscross

It is now in the queue for this repository.

… r=oli-obk,traviscross Report never type lints in dependencies This PR marks never type lints (`never_type_fallback_flowing_into_unsafe` & `dependency_on_unit_never_type_fallback`) to be included in cargo's reports / to be emitted when they happen in dependencies. This PR is based on rust-lang#141936 r? oli-obk

Rollup of 9 pull requests Successful merges: - #133952 (Remove wasm legacy abi) - #134661 (Reduce precedence of expressions that have an outer attr) - #141769 (Move metadata object generation for dylibs to the linker code ) - #141864 (Handle win32 separator for cygwin paths) - #141937 (Report never type lints in dependencies) - #142347 (Async drop - fix for StorageLive/StorageDead codegen for pinned future) - #142389 (Apply ABI attributes on return types in `rustc_codegen_cranelift`) - #142470 (Add some missing mailmap entries) - #142481 (Add `f16` inline asm support for LoongArch) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 10 pull requests Successful merges: - #133952 (Remove wasm legacy abi) - #134661 (Reduce precedence of expressions that have an outer attr) - #141769 (Move metadata object generation for dylibs to the linker code ) - #141937 (Report never type lints in dependencies) - #142347 (Async drop - fix for StorageLive/StorageDead codegen for pinned future) - #142389 (Apply ABI attributes on return types in `rustc_codegen_cranelift`) - #142470 (Add some missing mailmap entries) - #142481 (Add `f16` inline asm support for LoongArch) - #142499 (Remove check run bootstrap) - #142543 (Suggest adding semicolon in user code rather than macro impl details) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #141937 - WaffleLapkin:never-report-in-deps, r=oli-obk,traviscross Report never type lints in dependencies This PR marks never type lints (`never_type_fallback_flowing_into_unsafe` & `dependency_on_unit_never_type_fallback`) to be included in cargo's reports / to be emitted when they happen in dependencies. This PR is based on #141936 r? oli-obk

Pkgsrc changes: * Adjust patches to adapt to upstream changes and new versions. * assosicated checksums Upstream changes relative to 1.88.0: Version 1.89.0 (2025-08-07) ========================== Language -------- - [Stabilize explicitly inferred const arguments (`feature(generic_arg_infer)`)] (rust-lang/rust#141610) - [Add a warn-by-default `mismatched_lifetime_syntaxes` lint.] (rust-lang/rust#138677) This lint detects when the same lifetime is referred to by different syntax categories between function arguments and return values, which can be confusing to read, especially in unsafe code. This lint supersedes the warn-by-default `elided_named_lifetimes` lint. - [Expand `unpredictable_function_pointer_comparisons` to also lint on function pointer comparisons in external macros] (rust-lang/rust#134536) - [Make the `dangerous_implicit_autorefs` lint deny-by-default] (rust-lang/rust#141661) - [Stabilize the avx512 target features] (rust-lang/rust#138940) - [Stabilize `kl` and `widekl` target features for x86] (rust-lang/rust#140766) - [Stabilize `sha512`, `sm3` and `sm4` target features for x86] (rust-lang/rust#140767) - [Stabilize LoongArch target features `f`, `d`, `frecipe`, `lasx`, `lbt`, `lsx`, and `lvz`] (rust-lang/rust#135015) - [Remove `i128` and `u128` from `improper_ctypes_definitions`] (rust-lang/rust#137306) - [Stabilize `repr128` (`#[repr(u128)]`, `#[repr(i128)]`)] (rust-lang/rust#138285) - [Allow `#![doc(test(attr(..)))]` everywhere] (rust-lang/rust#140560) - [Extend temporary lifetime extension to also go through tuple struct and tuple variant constructors] (rust-lang/rust#140593) Compiler -------- - [Default to non-leaf frame pointers on aarch64-linux] (rust-lang/rust#140832) - [Enable non-leaf frame pointers for Arm64EC Windows] (rust-lang/rust#140862) - [Set Apple frame pointers by architecture] (rust-lang/rust#141797) Platform Support ---------------- - [Add new Tier-3 targets `loongarch32-unknown-none` and `loongarch32-unknown-none-softfloat`] (rust-lang/rust#142053) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. [platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html Libraries --------- - [Specify the base path for `file!`] (rust-lang/rust#134442) - [Allow storing `format_args!()` in a variable] (rust-lang/rust#140748) - [Add `#[must_use]` to `[T; N]::map`] (rust-lang/rust#140957) - [Implement `DerefMut` for `Lazy{Cell,Lock}`] (rust-lang/rust#129334) - [Implement `Default` for `array::IntoIter`] (rust-lang/rust#141574) - [Implement `Clone` for `slice::ChunkBy`] (rust-lang/rust#138016) - [Implement `io::Seek` for `io::Take`] (rust-lang/rust#138023) Stabilized APIs --------------- - [`NonZero<char>`] (https://doc.rust-lang.org/stable/std/num/struct.NonZero.html) - Many intrinsics for x86, not enumerated here - [AVX512 intrinsics](rust-lang/rust#111137) - [`SHA512`, `SM3` and `SM4` intrinsics] (rust-lang/rust#126624) - [`File::lock`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock) - [`File::lock_shared`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock_shared) - [`File::try_lock`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock) - [`File::try_lock_shared`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock_shared) - [`File::unlock`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.unlock) - [`NonNull::from_ref`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_ref) - [`NonNull::from_mut`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_mut) - [`NonNull::without_provenance`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.without_provenance) - [`NonNull::with_exposed_provenance`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.with_exposed_provenance) - [`NonNull::expose_provenance`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.expose_provenance) - [`OsString::leak`] (https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.leak) - [`PathBuf::leak`] (https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.leak) - [`Result::flatten`] (https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.flatten) - [`std::os::linux::net::TcpStreamExt::quickack`] (https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.quickack) - [`std::os::linux::net::TcpStreamExt::set_quickack`] (https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.set_quickack) These previously stable APIs are now stable in const contexts: - [`<[T; N]>::as_mut_slice`] (https://doc.rust-lang.org/stable/std/primitive.array.html#method.as_mut_slice) - [`<[u8]>::eq_ignore_ascii_case`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#impl-%5Bu8%5D/method.eq_ignore_ascii_case) - [`str::eq_ignore_ascii_case`] (https://doc.rust-lang.org/stable/std/primitive.str.html#impl-str/method.eq_ignore_ascii_case) Cargo ----- - [`cargo fix` and `cargo clippy --fix` now default to the same Cargo target selection as other build commands.] (rust-lang/cargo#15192) Previously it would apply to all targets (like binaries, examples, tests, etc.). The `--edition` flag still applies to all targets. - [Stabilize doctest-xcompile.] (rust-lang/cargo#15462) Doctests are now tested when cross-compiling. Just like other tests, it will use the [`runner` setting] (https://doc.rust-lang.org/cargo/reference/config.html#targettriplerunner) to run the tests. If you need to disable tests for a target, you can use the [ignore doctest attribute] (https://doc.rust-lang.org/rustdoc/write-documentation/documentation-tests.html#ignoring-targets) to specify the targets to ignore. Rustdoc ----- - [On mobile, make the sidebar full width and linewrap] (rust-lang/rust#139831). This makes long section and item names much easier to deal with on mobile. Compatibility Notes ------------------- - [Make `missing_fragment_specifier` an unconditional error] (rust-lang/rust#128425) - [Enabling the `neon` target feature on `aarch64-unknown-none-softfloat` causes a warning] (rust-lang/rust#135160) because mixing code with and without that target feature is not properly supported by LLVM - [Sized Hierarchy: Part I](rust-lang/rust#137944) - Introduces a small breaking change affecting `?Sized` bounds on impls on recursive types which contain associated type projections. It is not expected to affect any existing published crates. Can be fixed by refactoring the involved types or opting into the `sized_hierarchy` unstable feature. See the [FCP report] (rust-lang/rust#137944 (comment)) for a code example. - The warn-by-default `elided_named_lifetimes` lint is [superseded by the warn-by-default `mismatched_lifetime_syntaxes` lint.] (rust-lang/rust#138677) - [Error on recursive opaque types earlier in the type checker] (rust-lang/rust#139419) - [Type inference side effects from requiring element types of array repeat expressions are `Copy` are now only available at the end of type checking] (rust-lang/rust#139635) - [The deprecated accidentally-stable `std::intrinsics::{copy,copy_nonoverlapping,write_bytes}` are now proper intrinsics] (rust-lang/rust#139916). There are no debug assertions guarding against UB, and they cannot be coerced to function pointers. - [Remove long-deprecated `std::intrinsics::drop_in_place`] (rust-lang/rust#140151) - [Make well-formedness predicates no longer coinductive] (rust-lang/rust#140208) - [Remove hack when checking impl method compatibility] (rust-lang/rust#140557) - [Remove unnecessary type inference due to built-in trait object impls] (rust-lang/rust#141352) - [Lint against "stdcall", "fastcall", and "cdecl" on non-x86-32 targets] (rust-lang/rust#141435) - [Future incompatibility warnings relating to the never type (`!`) are now reported in dependencies] (rust-lang/rust#141937) - [Ensure `std::ptr::copy_*` intrinsics also perform the static self-init checks] (rust-lang/rust#142575) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Correctly un-remap compiler sources paths with the `rustc-dev` component] (rust-lang/rust#142377)

rustbot assigned oli-obk Jun 2, 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 Jun 2, 2025

traviscross added T-lang Relevant to the language team needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. and removed T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 3, 2025

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 Jun 3, 2025

traviscross added I-lang-nominated Nominated for discussion during a lang team meeting. P-lang-drag-1 Lang team prioritization drag level 1. https://rust-lang.zulipchat.com/#narrow/channel/410516-t-lang labels Jun 3, 2025

report never type lints in deps

851129f

WaffleLapkin force-pushed the never-report-in-deps branch from dd912ec to 851129f Compare June 3, 2025 18:02

oli-obk approved these changes Jun 4, 2025

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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 Jun 4, 2025

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 Jun 4, 2025

traviscross removed I-lang-nominated Nominated for discussion during a lang team meeting. P-lang-drag-1 Lang team prioritization drag level 1. https://rust-lang.zulipchat.com/#narrow/channel/410516-t-lang labels Jun 4, 2025

traviscross mentioned this pull request Jun 4, 2025

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

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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 Jun 14, 2025

rfcbot added the to-announce Announce this issue on triage meeting label Jun 14, 2025

rustbot mentioned this pull request Jun 14, 2025

Tracking issue for release notes of #141937: Report never type lints in dependencies #142512

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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 Jun 15, 2025

fmease mentioned this pull request Jun 15, 2025

Rollup of 9 pull requests #142545

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fmease mentioned this pull request Jun 15, 2025

Rollup of 10 pull requests #142550

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bors merged commit 8b35ae3 into rust-lang:master Jun 16, 2025
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rustbot added this to the 1.89.0 milestone Jun 16, 2025

WaffleLapkin deleted the never-report-in-deps branch June 19, 2025 15:20

apiraino removed the to-announce Announce this issue on triage meeting label Jun 26, 2025

cuviper mentioned this pull request Jul 17, 2025

Draft release notes for 1.89.0 #144097

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jieyouxu added L-never_type_fallback_flowing_into_unsafe Lint: never_type_fallback_flowing_into_unsafe L-dependency_on_unit_never_type_fallback Lint: dependency_on_unit_never_type_fallback A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. labels Jul 21, 2025

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