Remove unused features by mu001999 · Pull Request #152469 · rust-lang/rust

mu001999 · 2026-02-11T06:37:49Z

Detected by #152164.

~~Only allow unused_features if there are complex platform-specific features enabled.~~

rustbot · 2026-02-11T06:39:00Z

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rustbot · 2026-02-11T06:39:03Z

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Nadrieril · 2026-02-11T22:26:58Z

Hi, thanks for your contribution!

We should not remove these feature gates from tests. Features in tests sometimes test very subtle interactions and we don't want to break that. Also for tools and rustdoc we generally don't touch these directories unless strictly necessary; we're not running their whole test suite in CI so we could be removing a feature they actually use.

I'm also of the opinion that replacing a feature with cfg_attr(..., feature(...)) is noise and not worth the precision. E.g. all the platform-specific stuff in core.

The rest looks good to me, that's some nice cleanups.

mu001999 · 2026-02-12T01:29:58Z

@Nadrieril Make sense, I will keep the removal in compiler and replace the rest with just allowing unused_features

rustbot · 2026-02-12T07:37:54Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

Nadrieril · 2026-02-12T13:22:04Z

Wait, is the plan to enable unused_features as warn-by-default? Or maybe just set it up to warn in the compiler? That would change things.

This should at least not be enabled in tests, just like we pass -Aunused in tests. In fact I'm surprised this isn't enough: isn't unused_features part of the unused lint group? (or am I wrong that we pass -Aunused to tests?).

mu001999 · 2026-02-12T13:52:08Z

Is the plan to enable unused_features as warn-by-default?

I think the plan is warn-by-default, at least for me

Isn't unused_features part of the unused lint group

unused_features is part of unused, but not all tests will pass -Aunused, see https://rustc-dev-guide.rust-lang.org/tests/ui.html?highlight=ui#ui-test-mode-preset-lint-levels

mu001999 · 2026-02-13T01:31:00Z

Considering that #![allow(unused_features)] is currently useless, I think commits related to tests and tools that only add #![allow(unused_features)] should be merged together with the unused_features lint itself.

Nadrieril · 2026-02-13T02:23:36Z

library/std/src/num/f128.rs

 use crate::sys::cmath;

 #[cfg(not(test))]
+#[doc(test(attr(allow(unused_features))))]


What's that syntax? I've not seen this attribute before

See https://doc.rust-lang.org/rustdoc/write-documentation/documentation-tests.html#pre-processing-examples, and after #140560, we can use it everywhere.

Nadrieril

I think commits related to tests and tools that only add #![allow(unused_features)] should be merged together with the unused_features lint itself.

Yeah agreed, and your PR looks good to me now, just a tiny question above.

View changes since this review

jdonszelmann · 2026-02-13T11:17:17Z

@bors r=nadriril,jdonszelmann

rust-bors · 2026-02-13T11:17:20Z

📌 Commit 73c42c1 has been approved by nadriril,jdonszelmann

It is now in the queue for this repository.

⚠️ The following reviewer(s) could not be found: nadriril

jdonszelmann · 2026-02-13T11:17:39Z

@bors r=nadrieril,jdonszelmann

rust-bors · 2026-02-13T11:17:42Z

📌 Commit 73c42c1 has been approved by nadrieril,jdonszelmann

It is now in the queue for this repository.

…atures, r=nadrieril,jdonszelmann Remove unused features Detected by rust-lang#152164. ~~Only allow `unused_features` if there are complex platform-specific features enabled.~~

…uwer Rollup of 14 pull requests Successful merges: - #152323 (Fix ICE in borrowck when recovering `fn_sig` for `-> _`) - #152469 (Remove unused features) - #152515 (Extract `DepKindVTable` constructors to their own module) - #152555 (Port `#[rustc_diagnostic_item]` to the new attribute parsers) - #152218 (Report unconstrained region in hidden types lazily) - #152356 (Improve the `inline_fluent!` macro) - #152392 (Fix ICE in supertrait_vtable_slot when supertrait has missing generics) - #152407 (Add regression test for type_const with unit struct ctor under mGCA) - #152440 (Fix typos and grammar in compiler and build documentation) - #152536 (bootstrap: add explicit UTF-8 encoding to text-mode open() calls) - #152554 (Remove `deprecated_safe` and its corresponding feature gate) - #152556 (doc: move riscv64a23-unknown-linux-gnu to tier 2) - #152563 (Replace "bug" with "issue" in triagebot ping messages) - #152565 (fix missleading error for tuple ctor) Failed merges: - #152512 (core: Implement feature `float_exact_integer_constants`) - #152296 (Port `rust_nonnull_optimization_guaranteed` and `rustc_do_not_const_check` to the new attribute parser)

Rollup merge of #152469 - mu001999-contrib:cleanup/unused-features, r=nadrieril,jdonszelmann Remove unused features Detected by #152164. ~~Only allow `unused_features` if there are complex platform-specific features enabled.~~

…atures, r=nadrieril,jdonszelmann Remove unused features Detected by rust-lang#152164. ~~Only allow `unused_features` if there are complex platform-specific features enabled.~~

kleisauke · 2026-02-26T10:48:52Z

library/panic_unwind/src/lib.rs

 #![feature(cfg_emscripten_wasm_eh)]
 #![feature(cfg_select)]
 #![feature(core_intrinsics)]
-#![feature(lang_items)]


Emscripten needs this feature.

rust/library/panic_unwind/src/emcc.rs

Line 40 in 1ed4882

#[lang = "eh_catch_typeinfo"]

error[E0658]: lang items are subject to change --> /rustc/1ed488274bec5bf5cfe6bf7a1cc089abcc4ebd68/library/panic_unwind/src/emcc.rs:40:1 | 40 | #[lang = "eh_catch_typeinfo"] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = help: add `#![feature(lang_items)]` to the crate attributes to enable = note: this compiler was built on 2026-02-25; consider upgrading it if it is out of date For more information about this error, try `rustc --explain E0658`. error: could not compile `panic_unwind` (lib) due to 1 previous error warning: build failed, waiting for other jobs to finish...

Oops, I will recover this for emscripten

No worries, it's only needed when compiling with RUSTFLAGS="-Zemscripten-wasm-eh=false", which will be removed in the future.

…oboet Recover feature lang_items for emscripten Fixes rust-lang#152469 (comment)

Rollup merge of #153128 - mu001999-contrib:fix/features, r=joboet Recover feature lang_items for emscripten Fixes #152469 (comment)

…oboet Recover feature lang_items for emscripten Fixes rust-lang#152469 (comment) The previous rust-lang#153128 lacks of `feature`

Rollup merge of #153255 - mu001999-contrib:fix/features, r=joboet Recover feature lang_items for emscripten Fixes #152469 (comment) The previous #153128 lacks of `feature`

mu001999 marked this pull request as ready for review February 11, 2026 06:38

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 11, 2026

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rustbot assigned jdonszelmann Feb 11, 2026

mu001999 force-pushed the cleanup/unused-features branch from aa64776 to b391897 Compare February 12, 2026 03:47

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mu001999 force-pushed the cleanup/unused-features branch from b391897 to 2833eea Compare February 12, 2026 07:37

mu001999 force-pushed the cleanup/unused-features branch from 2833eea to 41b83c2 Compare February 12, 2026 07:43

mu001999 added 4 commits February 13, 2026 09:25

Remove unused features in compiler

a07f837

Remove unused features in library

0dc1556

Remove unused features in librustdoc

a318a20

Remove or allow unused features in library doc and tests

73c42c1

mu001999 force-pushed the cleanup/unused-features branch from 41b83c2 to 73c42c1 Compare February 13, 2026 01:27

Nadrieril reviewed Feb 13, 2026

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JonathanBrouwer mentioned this pull request Feb 13, 2026

Rollup of 14 pull requests #152571

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This was referenced Feb 13, 2026

Rollup of 14 pull requests #152572

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Rollup of 14 pull requests #152574

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rust-bors bot merged commit 65d982a into rust-lang:main Feb 14, 2026
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rustbot added this to the 1.95.0 milestone Feb 14, 2026

rust-timer mentioned this pull request Feb 19, 2026

Rollup of 18 pull requests #152825

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kleisauke reviewed Feb 26, 2026

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mu001999 deleted the cleanup/unused-features branch February 26, 2026 11:29

mu001999 mentioned this pull request Feb 26, 2026

Recover feature lang_items for emscripten #153128

Merged

JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Feb 26, 2026

Rollup merge of rust-lang#153128 - mu001999-contrib:fix/features, r=j…

5303a74

…oboet Recover feature lang_items for emscripten Fixes rust-lang#152469 (comment)

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Feb 27, 2026

Rollup merge of rust-lang#153128 - mu001999-contrib:fix/features, r=j…

1963be1

…oboet Recover feature lang_items for emscripten Fixes rust-lang#152469 (comment)

JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Feb 27, 2026

Rollup merge of rust-lang#153128 - mu001999-contrib:fix/features, r=j…

44427f2

…oboet Recover feature lang_items for emscripten Fixes rust-lang#152469 (comment)

JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Feb 27, 2026

Rollup merge of rust-lang#153128 - mu001999-contrib:fix/features, r=j…

6c425a0

…oboet Recover feature lang_items for emscripten Fixes rust-lang#152469 (comment)

JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Feb 27, 2026

Rollup merge of rust-lang#153128 - mu001999-contrib:fix/features, r=j…

5bb3260

…oboet Recover feature lang_items for emscripten Fixes rust-lang#152469 (comment)

rust-timer added a commit that referenced this pull request Feb 28, 2026

Unrolled build for #153128

9e9654a

Rollup merge of #153128 - mu001999-contrib:fix/features, r=joboet Recover feature lang_items for emscripten Fixes #152469 (comment)

mu001999 restored the cleanup/unused-features branch February 28, 2026 13:26

mu001999 mentioned this pull request Mar 1, 2026

Recover feature lang_items for emscripten #153255

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rust-timer added a commit that referenced this pull request Mar 1, 2026

Unrolled build for #153255

8d9da89

Rollup merge of #153255 - mu001999-contrib:fix/features, r=joboet Recover feature lang_items for emscripten Fixes #152469 (comment) The previous #153128 lacks of `feature`

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