Hello and welcome to another issue of This Week in Rust! Rust is a programming language empowering everyone to build reliable and efficient software. This is a weekly summary of its progress and community. Want something mentioned? Tag us at @ThisWeekInRust on Twitter or @ThisWeekinRust on mastodon.social, or send us a pull request. Want to get involved? We love contributions.

This Week in Rust is openly developed on GitHub and archives can be viewed at this-week-in-rust.org. If you find any errors in this week's issue, please submit a PR.

Updates from Rust Community

Official

• Announcing async fn and return-position impl Trait in traits
• Rustc Trait System Refactor Initiative Update: A call for testing

Foundation

• Improving Supply Chain Security for Rust Through Artifact Signing

Project/Tooling Updates

• 2023: Slint in Review
• Introducing Loco: The Rails of Rust

Observations/Thoughts

• My path to becoming a Rustacean
• Memory Safety is a Red Herring
• The Most Common Rust Compiler Errors as Encountered in RustRover: Part 2
• My reference was dropped, why is the compiler complaining about multiple borrows?
• Can CppRef be ergonomic?
• [video] Rust 1.74.1 & Rust News

Rust Walkthroughs

• The dark side of inlining and monomorphization
• The Heart of a Language Server
• Rust: Multi threading
• [series] Meilisearch Expands Search Power with Arroy's Filtered Disk ANN
• Encrypted Portals between Macs – built in Rust and Swift (sorta similar to ngrok and tailscale)
• [video] Error handling in Rust

Miscellaneous

• An anonymous survey about mutable statics
• Web development in Rust
• Rocket: Web-based Hello World! with tests

Crate of the Week

This week's crate is rouille, a small synchronous web framework.

Thanks to Peter Puetz for the suggestion!

Please submit your suggestions and votes for next week!

Call for Participation; projects and speakers

CFP - Projects

Always wanted to contribute to open-source projects but did not know where to start? Every week we highlight some tasks from the Rust community for you to pick and get started!

Some of these tasks may also have mentors available, visit the task page for more information.

• greptimedb - Add more tables into information_schema for better compatibility
• Ockam - Check that the bootstrap_server command argument is a valid host:port
• Ockam - Refactor to use typed interfaces
• Ockam - Check structs comply with the cddl schema

If you are a Rust project owner and are looking for contributors, please submit tasks here.

CFP - Speakers

Are you a new or experienced speaker looking for a place to share something cool? This section highlights events that are being planned and are accepting submissions to join their event as a speaker.

• No new calls for speakers this week

If you are an event organizer hoping to expand the reach of your event, please submit a link to the submission website either through a PR to TWiR or on the [Rust-lang forums].[link TBD]

Updates from the Rust Project

268 pull requests were merged in the last week

• add support for for await loops
• add illumos aarch64 target for rust
• add support for hexagon-unknown-none-elf as target
• -Znext-solver: adapt overflow rules to avoid breakage
• rustc_codegen_ssa: Don't drop IncorrectCguReuseType , make rustc_expected_cgu_reuse attr work
• subtype_predicate: remove unnecessary probe
• add check for possible CStr literals in pre-2021
• add method to get instance instantiation arguments
• add missing feature gate for sanitizer CFI cfgs
• avoid redundant Option for cross_crate_inlinable
• coverage: check for async fn explicitly, without needing a heuristic
• do not allow ABI mismatches inside repr(C) types
• do not fetch HIR in inferred_outlives_of
• emit better suggestions for &T == T and T == &T
• emits error if has bound regions
• encode CoroutineKind directly
• exhaustiveness: improve complexity on some wide matches
• exhaustiveness: keep the original thir::Pat around
• exhaustiveness: reveal empty opaques in depth
• exhaustiveness: reveal opaque types properly
• fallback default to None during ast-lowering for lifetime binder
• fix ICE when using raw ptr in a pattern
• fix crash due to CrateItem::kind() not handling constructors
• give temporaries in if let guards correct scopes
• make soft_unstable show up in future breakage reports
• make closures carry their own ClosureKind
• mark ty::Const::Error when meet unsupport ty for const generic params
• pass DeadItem and lint as consistent group in dead-code
• remove DiagCtxt API duplication
• remove metadata decoding DefPathHash cache
• resolve: eagerly feed closure visibilities
• resolve: feed visibilities for unresolved trait impl items
• resolve: stop feeding visibilities for import list stems
• rework -Zverbose
• simple modification of non_lifetime_binders's diagnostic information to adapt to type binders
• skip duplicate stable crate ID encoding into metadata
• split coroutine desugaring kind from source
• subtree sync for rustc_codegen_cranelift
• suggest = to == in more cases, even in the face of reference mismatch
• add function ABI and type layout to StableMIR
• separate MIR lints from validation
• miri: implement and test simd_masked_load and simd_masked_store
• improve coding efficiency for RawDefId
• use Vec for region constraints instead of BTreeMap
• stabilize file_create_new
• stabilize ip_in_core feature
• add more niches to rawvec
• add IntoAsyncIterator
• add hint::assert_unchecked
• cargo: extend the build directive syntax with cargo::
• cargo: hold the mutate exclusive lock when vendoring
• cargo: refactor: centralize git checkouts and db paths
• cargo: refactor: custom error types for cargo-util-schemas
• cargo: rework --check-cfg generation comment
• rustdoc: Add is_object_safe information for traits in JSON output
• rustdoc: fix display of warning block if it is first element of the top doc block
• clippy: question_mark: also trigger on return statements
• clippy: check whether out of bound when access a known length array with a constant index
• clippy: do not consider async { (impl IntoFuture).await } as redundant
• clippy: extend UNNECESSARY_TO_OWNED to handle split
• clippy: move uninhabited_references to nursery
• clippy: new lints iter_filter_is_some and iter_filter_is_ok
• clippy: stop bool_comparison's suggestion from consuming parentheses
• rust-analyzer: complete exported macros in #[macro_use($0)]
• rust-analyzer: implement a rust-analyzer span backed proc-macro server mode
• rust-analyzer: auto remove unnecessary braces after remove unused imports
• rust-analyzer: correctly set and mark the proc-macro spans
• rust-analyzer: fix completions analysis not caching all nodes in Semantics
• rust-analyzer: fix span marking for builtin fn macros
• rust-analyzer: fully remove dummy spans
• rust-analyzer: remove wrong comma after remove unnecessary braces

Rust Compiler Performance Triage

Some of the recent noise swings have been appearing again this week, but luckily less often than before. There were a few actual regressions, but most of them were localized to a single stress test. On the other hand, there were a few very nice wins across the board, especially for check and incremental builds, primarily thanks to #118824 and #119265.

Triage done by @kobzol. Revision range: bf9229a2e366b4c311f059014a4aa08af16de5d8..1ab783112ab4e4807304dbd249b39771246013ef

Summary:

5 Regressions, 7 Improvements, 2 Mixed; 1 of them in rollups 58 artifact comparisons made in total

Full report here

Approved RFCs

Changes to Rust follow the Rust RFC (request for comments) process. These are the RFCs that were approved for implementation this week:

• No RFCs were approved this week.

Final Comment Period

Every week, the team announces the 'final comment period' for RFCs and key PRs which are reaching a decision. Express your opinions now.

RFCs

• No RFCs entered Final Comment Period this week.

Tracking Issues & PRs

• [disposition: merge] Use version-sorting for all sorting
• [disposition: merge] Tracking issue for exclusive range patterns
• [disposition: merge] rustdoc: clean up source sidebar hide button

Language Reference

• No Language Reference RFCs entered Final Comment Period this week.

Unsafe Code Guidelines

• No Unsafe Code Guideline RFCs entered Final Comment Period this week.

New and Updated RFCs

• RFC: Allow type inference for const or static

Call for Testing

An important step for RFC implementation is for people to experiment with the implementation and give feedback, especially before stabilization. The following RFCs would benefit from user testing before moving forward:

• No RFCs issued a call for testing this week.

If you are a feature implementer and would like your RFC to appear on the above list, add the new call-for-testing label to your RFC along with a comment providing testing instructions and/or guidance on which aspect(s) of the feature need testing.

Upcoming Events

Rusty Events between 2023-12-27 - 2024-01-24 🦀

Virtual

• 2023-12-28 | Virtual (Charlottesville, NC, US) | Charlottesville Rust Meetup
  • Crafting Interpreters in Rust Collaboratively
• 2024-01-03 | Virtual (Indianapolis, IN, US) | Indy Rust
  • Indy.rs - with Social Distancing
• 2024-01-09 | Virtual (Dallas, TX, US) | Dallas Rust
  • Last Tuesday
• 2024-01-11 | Virtual (Charlottesville, NC, US) | Charlottesville Rust Meetup
  • Crafting Interpreters in Rust Collaboratively
• 2024-01-16 | Virtual (Washington, DC, US) | Rust DC
  • Mid-month Rustful

Europe

• 2023-12-27 | Copenhagen, DK | Copenhagen Rust Community
  • Rust hacknight #1: CLIs, TUIs and plushies
• 2023-12-28 | Vienna, AT | Rust Vienna
  • Rust Dojo 3: Holiday Edition
• 2024-01-11 | Reading, UK | Reading Rust Workshop
  • Reading Rust Meetup at Browns
• 2024-01-11 | Wrocław, PL | Rust Wrocław
  • Rust Meetup #36
• 2024-01-13 | Helsinki, FI | Finland Rust-lang Group
  • January Meetup

North America

• 2023-12-27 | Austin, TX, US | Rust ATX
  • Rust Lunch - Fareground
• 2024-01-06 | Boston, MA, US | Boston Rust Meetup
  • Beacon Hill Rust Lunch
• 2024-01-08 | Chicago, IL, US | Deep Dish Rust
  • Rust Hack Night
• 2024-01-09 | Seattle, WA, US | Cap Hill Rust Coding/Hacking/Learning
  • Rusty Coding/Hacking/Learning Night
• 2024-01-09 | Minneapolis, MN, US | Minneapolis Rust Meetup
  • Minneapolis Rust Meetup Happy Hour
• 2024-01-14 | Cambridge, MA, US | Boston Rust Meetup
  • Alewife Rust Lunch
• 2024-01-16 | San Francisco, CA, US | San Francisco Rust Study Group
  • Rust Hacking in Person
• 2024-01-17 | Chicago, IL, US | Deep Dish Rust
  • Rust Happy Hour

If you are running a Rust event please add it to the calendar to get it mentioned here. Please remember to add a link to the event too. Email the Rust Community Team for access.

Jobs

Please see the latest Who's Hiring thread on r/rust

Quote of the Week

Rust can be rather more verbose than C; there are a lot of invariants that have to be expressed in the code. But that is countered by the need for far less error-handling code; it turns out to be a wash, with the size of the two implementations being about the same.

– Alice Ryhl at the Linux Plumbers Conference as quoted by Jonathan Corbet, LWN

Thanks to Ivan Fraixedes for the suggestion!

Please submit quotes and vote for next week!

This Week in Rust is edited by: nellshamrell, llogiq, cdmistman, ericseppanen, extrawurst, andrewpollack, U007D, kolharsam, joelmarcey, mariannegoldin, bennyvasquez.

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Discuss on r/rust