Move `std::io::ErrorKind` to `core::io` by bushrat011899 · Pull Request #154654 · rust-lang/rust

bushrat011899 · 2026-04-01T01:07:08Z

ACP: rust-lang/libs-team#755
Tracking issue: #154046
Related: #152918

Description

I consider #154046 to be really important for no_std, but I'm concerned #152918 might be too controversial. As an alternative, I'd like to propose starting small with ErrorKind, since it can be moved somewhat trivially. It has no dependencies on functionality in std, no platform specific behaviour, and could provide an excellent bridging point for no_std IO libraries.

Since std::io::Error implements From<ErrorKind>, libraries could write functions which return Result<T, core::io::ErrorKind>, and therefore be usable in std-using libraries with the ? operator. For that reason, I'd consider this to be a worthwhile change even if the rest of std::io couldn't be moved to core/alloc, and entirely compatible with any efforts to make such a change in the future.

Notes

This is my first PR against Rust, please let me know if there's anything I should be doing that I have not done. I tried reading through the library contributors guide but I'm sure I've missed something.
No AI tooling of any kind was used in the creation of this PR.
I believe it's appropriate that this be a part of the linked tracking issue, but please let me know if that's not the case!

rustbot · 2026-04-01T01:07:13Z

r? @Mark-Simulacrum

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Owners of files modified in this PR: @ChrisDenton, libs
@ChrisDenton, libs expanded to 8 candidates

a1phyr · 2026-04-01T11:51:29Z

I'm concerned #152918 might be too controversial.

It may be controversial, but it has been accepted in principle by libs-teams, so it should be fine.

bushrat011899 · 2026-04-01T12:12:13Z

I'm concerned #152918 might be too controversial.

It may be controversial, but it has been accepted in principle by libs-teams, so it should be fine.

I hope so! I really want your PR to land. Regardless of whether it does, this is a good follow-up to go further at basically no cost.

lygstate · 2026-04-01T18:35:45Z

looks good to me

…r=Mark-Simulacrum Move `std::io::ErrorKind` to `core::io` ACP: rust-lang/libs-team#755 Tracking issue: rust-lang#154046 Related: rust-lang#152918 ## Description I consider rust-lang#154046 to be really important for `no_std`, but I'm concerned rust-lang#152918 might be too controversial. As an alternative, I'd like to propose starting small with `ErrorKind`, since it can be moved somewhat trivially. It has no dependencies on functionality in `std`, no platform specific behaviour, and could provide an excellent bridging point for `no_std` IO libraries. Since `std::io::Error` implements `From<ErrorKind>`, libraries could write functions which return `Result<T, core::io::ErrorKind>`, and therefore be usable in `std`-using libraries with the `?` operator. For that reason, I'd consider this to be a worthwhile change even if the rest of `std::io` couldn't be moved to `core`/`alloc`, and entirely compatible with any efforts to make such a change in the future. ## Notes * This is my first PR against Rust, please let me know if there's anything I should be doing that I have not done. I tried reading through the library contributors guide but I'm sure I've missed _something_. * No AI tooling of any kind was used in the creation of this PR. * I believe it's appropriate that this be a part of the linked tracking issue, but please let me know if that's not the case!

Rollup of 6 pull requests Successful merges: - #154654 (Move `std::io::ErrorKind` to `core::io`) - #155054 (constify `Index(Mut)`, `Deref(Mut)` for `Vec`) - #155507 (suggest expect instead of unwrap when arg provided) - #154664 (core/num: Implement feature `integer_cast_extras`) - #155474 (Rename incremental `cfail`/`cpass` revisions to `bfail`/`bpass`) - #155493 (docs(num): fix stale link to `mem::Alignment`)

JonathanBrouwer · 2026-04-20T06:13:29Z

@bors r-
#155534 (comment)

rust-bors · 2026-04-20T06:13:36Z

This pull request was unapproved.

This PR was contained in a rollup (#155534), which was unapproved.

Move `std::io::ErrorKind` to `core::io` * Update `rustdoc-html` tests for the new path * Add `core_io` feature to control stability. This replaces the use of `core_io_borrowed_buf` on the `core::io` module itself. * Re-export `core::io::ErrorKind` in `std::io::error`

bushrat011899 · 2026-04-20T08:42:17Z

@rustbot ready
I assumed all instances of #![feature(core_io_borrowed_buf)] would need to include #![feature(core_io)], but that's not the case for documentation tests from the looks of it. Unfortunate that it wasn't caught in CI. I'm very sorry for these little mistakes!

JonathanBrouwer · 2026-04-20T08:47:56Z

@bors try jobs=aarch64-msvc-1

Move `std::io::ErrorKind` to `core::io` try-job: aarch64-msvc-1

rust-bors · 2026-04-20T11:13:49Z

☀️ Try build successful (CI)
Build commit: 4388fd1 (4388fd113335ef85115dddb6c3a59ec4411fc4db, parent: e22c616e4e87914135c1db261a03e0437255335e)

JonathanBrouwer · 2026-04-20T11:50:15Z

@bors r=Mark-Simulacrum

No worries about the little mistakes btw, these are very common and there's not much you can do to prevent them :3

rust-bors · 2026-04-20T11:50:19Z

📌 Commit fe2b39f has been approved by Mark-Simulacrum

It is now in the queue for this repository.

…uwer Rollup of 11 pull requests Successful merges: - #154654 (Move `std::io::ErrorKind` to `core::io`) - #145270 (Fix an ICE observed with an explicit tail-call in a default trait method) - #154895 (borrowck: Apply `user_arg_index` nomenclature more broadly) - #155213 (resolve: Make sure visibilities of import declarations make sense) - #155346 (`single_use_lifetimes`: respect `anonymous_lifetime_in_impl_trait`) - #155517 (Add a test for Mach-O `#[link_section]` API inherited from LLVM) - #155549 (Remove some unnecessary lifetimes.) - #154248 (resolve : mark repr_simd as internal) - #154772 (slightly optimize the `non-camel-case-types` lint) - #155541 (Add `#[rust_analyzer::prefer_underscore_import]` to the traits in `rustc_type_ir::inherent`) - #155544 (bootstrap: Make "detected modifications" for download-rustc less verbose)

Rollup merge of #154654 - bushrat011899:core_io_error_kind, r=Mark-Simulacrum Move `std::io::ErrorKind` to `core::io` ACP: rust-lang/libs-team#755 Tracking issue: #154046 Related: #152918 ## Description I consider #154046 to be really important for `no_std`, but I'm concerned #152918 might be too controversial. As an alternative, I'd like to propose starting small with `ErrorKind`, since it can be moved somewhat trivially. It has no dependencies on functionality in `std`, no platform specific behaviour, and could provide an excellent bridging point for `no_std` IO libraries. Since `std::io::Error` implements `From<ErrorKind>`, libraries could write functions which return `Result<T, core::io::ErrorKind>`, and therefore be usable in `std`-using libraries with the `?` operator. For that reason, I'd consider this to be a worthwhile change even if the rest of `std::io` couldn't be moved to `core`/`alloc`, and entirely compatible with any efforts to make such a change in the future. ## Notes * This is my first PR against Rust, please let me know if there's anything I should be doing that I have not done. I tried reading through the library contributors guide but I'm sure I've missed _something_. * No AI tooling of any kind was used in the creation of this PR. * I believe it's appropriate that this be a part of the linked tracking issue, but please let me know if that's not the case!

…uwer Rollup of 11 pull requests Successful merges: - rust-lang/rust#154654 (Move `std::io::ErrorKind` to `core::io`) - rust-lang/rust#145270 (Fix an ICE observed with an explicit tail-call in a default trait method) - rust-lang/rust#154895 (borrowck: Apply `user_arg_index` nomenclature more broadly) - rust-lang/rust#155213 (resolve: Make sure visibilities of import declarations make sense) - rust-lang/rust#155346 (`single_use_lifetimes`: respect `anonymous_lifetime_in_impl_trait`) - rust-lang/rust#155517 (Add a test for Mach-O `#[link_section]` API inherited from LLVM) - rust-lang/rust#155549 (Remove some unnecessary lifetimes.) - rust-lang/rust#154248 (resolve : mark repr_simd as internal) - rust-lang/rust#154772 (slightly optimize the `non-camel-case-types` lint) - rust-lang/rust#155541 (Add `#[rust_analyzer::prefer_underscore_import]` to the traits in `rustc_type_ir::inherent`) - rust-lang/rust#155544 (bootstrap: Make "detected modifications" for download-rustc less verbose)

rustbot assigned Mark-Simulacrum Apr 1, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 1, 2026

rustbot added T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. T-rustdoc-frontend Relevant to the rustdoc-frontend team, which will review and decide on the web UI/UX output. labels Apr 1, 2026

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Mark-Simulacrum requested changes Apr 4, 2026

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Comment thread library/core/src/io/error.rs

Comment thread library/core/src/io/error.rs

Comment thread library/std/src/io/error/repr_bitpacked.rs Outdated

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jhpratt mentioned this pull request Apr 20, 2026

Rollup of 6 pull requests #155534

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rust-bors Bot pushed a commit that referenced this pull request Apr 20, 2026

Auto merge of #154654 - bushrat011899:core_io_error_kind, r=<try>

4388fd1

Move `std::io::ErrorKind` to `core::io` try-job: aarch64-msvc-1

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JonathanBrouwer mentioned this pull request Apr 20, 2026

Rollup of 11 pull requests #155552

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rust-bors Bot merged commit 3ca43dc into rust-lang:main Apr 20, 2026
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rustbot added this to the 1.97.0 milestone Apr 20, 2026

bushrat011899 mentioned this pull request Apr 20, 2026

Move std::io::RawOsError to core::io #155574

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