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

Rollup of 8 pull requests Successful merges: - #155370 (Add regression test for dead code elimination with drop + panic) - #154823 (Replace the spdx-rs dependency with a minimal in-tree SPDX tag-value parser) - #155352 (triagebot.toml: Sync `assign.owners` with `autolabel."T-compiler"`) - #155431 (Add temporary scope to assert_matches) - #152995 (ACP Implementation of PermissionsExt for Windows ) - #153873 (deprecate `std::char` constants and functions) - #154654 (Move `std::io::ErrorKind` to `core::io`) - #154865 (libtest: use binary search for --exact test filtering)

jhpratt · 2026-04-19T03:56:04Z

@bors r-

#155503 (comment)

rust-bors · 2026-04-19T03:56:10Z

This pull request was unapproved.

This PR was contained in a rollup (#155503), which was unapproved.

Certain links will not be valid when moved into `core::io`

* Checking exhaustion will no longer be possible for `repr_bitpacked`. Moving `kind_from_prim` into an associated function, and setting it up to be moved into `core::io` as well. * `ErrorKind::as_str` is private, but it's only usage is trivially replaced with `Display::fmt` * The features io_error_inprogress, io_error_more, and io_error_uncategorized will all need to be enabled

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`

rustbot · 2026-04-19T22:35:59Z

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.

Mark-Simulacrum · 2026-04-19T22:38:49Z

@bors try jobs=dist-various-*

Move `std::io::ErrorKind` to `core::io` try-job: dist-various-*

bushrat011899 · 2026-04-19T22:39:36Z

@rustbot ready
The issue was caused by one last usage of ErrorKind::as_str in std that I didn't notice (was only for the SGX platform). I've replaced that with a call to format!(...) since the original was immediately creating a String anyway. I could instead make ErrorKind::as_str pub/doc(hidden)/unstable/etc. but I think this is preferable.

rust-bors · 2026-04-20T00:00:37Z

☀️ Try build successful (CI)
Build commit: 7bcb437 (7bcb437e31bd41d44d2ad4448b4d7172a683ace1, parent: e22c616e4e87914135c1db261a03e0437255335e)

Mark-Simulacrum · 2026-04-20T01:23:30Z

@bors r+ rollup=iffy

rust-bors · 2026-04-20T01:23:33Z

📌 Commit 74d5469 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

…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.

bushrat011899 · 2026-04-20T06:30:41Z

    /// # Examples
    ///
    /// ```no_run
+    /// #![feature(core_io)]


This line is not required and was the cause of the roll-up failure. Will remove and update commit history once I'm back home.

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rustbot assigned Mark-Simulacrum Apr 1, 2026

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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

rustbot 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-review Status: Awaiting review from the assignee but also interested parties. labels Apr 4, 2026

jhpratt mentioned this pull request Apr 19, 2026

Rollup of 8 pull requests #155503

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bushrat011899 added 3 commits April 20, 2026 08:29

Make documentation for std::io::ErrorKind core::io compatible

08bd077

Certain links will not be valid when moved into `core::io`

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rust-bors bot pushed a commit that referenced this pull request Apr 19, 2026

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

7bcb437

Move `std::io::ErrorKind` to `core::io` try-job: dist-various-*

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Rollup of 6 pull requests #155534

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bushrat011899 commented Apr 20, 2026

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