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

Some changes occurred in exhaustiveness checking

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rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

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The Miri subtree was changed

cc @rust-lang/miri

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 · 2026-02-13T11:17:31Z

@bors r-

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)

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

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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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JonathanBrouwer mentioned this pull request Feb 13, 2026

Rollup of 14 pull requests #152572

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JonathanBrouwer mentioned this pull request Feb 13, 2026

Rollup of 14 pull requests #152574

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