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 X (formerly 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.

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Updates from Rust Community

Newsletters

• The Embedded Rustacean Issue #35
• Rust Trends Issue #56

Project/Tooling Updates

• musi lili retro game engine 0.1 released
• Nutype 0.5.1: better no_std support and bug fixes
• Ibis 0.2.0 - Federated Wiki with Shiny Redesign, based on Diesel, Actix and Leptos
• dagrs 0.4.2 - Flow-based Programming in Rust
• Avian Physics 0.2
• Slint 1.9
• gitoxide - december 2024

Observations/Thoughts

• Dropping Hyper
• Embedding Lua in sqleibniz with Rust
• What would it take to add refinement types to Rust?
• Context-Generic Programming
• Building a Secure Hierarchical Key Derivation System in Rust
• Streamlined dataflow analysis code in rustc
• Four limitations of Rust’s borrow checker
• A Review of Rust in 2024: What Next?
• My actions-rust-cross Action Now Has Built-In Caching
• Transforming Rust Development: How Windsurf AI Tripled Productivity

Rust Walkthroughs

• How to build and publish multi-platform Rust binaries via Github actions
• Compiling C to Safe Rust, Formalized
• Unnecessary Optimization in Rust: Hamming Distances, SIMD, and Auto-Vectorization

Miscellaneous

• Rust university course exercises
• [video] The SQLite Rewrite In Rust

Crate of the Week

This week's crate is OmniLED, a helper to display things like time or audio volumne on a LED matrix that some peripherials (such as gaming keyboards) have.

Thanks to llogiq for the suggestion!

Please submit your suggestions and votes for next week!

Calls 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:

RFCs

• No calls for testing were issued this week.

Rust

• No calls for testing were issued this week.

Rustup

• CfT: Test out Rustup's reqwest backend with rustls
• Testing steps

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.

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.

• Rama — provide constants for common (network) hosts to rama-net's Host
• Rama — support vec/array impl for DnsResolver
• Rama — support HAR exporter (http) layer in rama

If you are a Rust project owner and are looking for contributors, please submit tasks here or through a PR to TWiR or by reaching out on X (formerly Twitter) or Mastodon!

CFP - Events

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.

If you are an event organizer hoping to expand the reach of your event, please submit a link to the website through a PR to TWiR or by reaching out on X (formerly Twitter) or Mastodon!

Updates from the Rust Project

398 pull requests were merged in the last week

• -Znext-solver: modify candidate preference rules
• Variants::Single: do not use invalid VariantIdx for uninhabited enums
• rustc_borrowck: Suggest changing &raw const to &raw mut if applicable
• abstract ProcThreadAttributeList into its own struct
• add --doctest-compilation-args option to add compilation flags to doctest compilation
• add ignore-rustc-debug-assertions to tests/ui/associated-consts/issue-93775.rs
• align {i686,x86_64}-win7-windows-msvc to their parent targets
• also lint on option of function pointer comparisons
• always run tail_expr_drop_order lint in promoted MIR query
• begin to implement type system layer of unsafe binders
• cleanup TypeVerifier
• cleanup region handling: add LateParamRegionKind
• correctly note item kind in NonConstFunctionCall error message
• coverage: dismantle map_data.rs by moving its responsibilities elsewhere
• coverage: store coverage source regions as Span until codegen (take 2)
• detect invalid exprs in parser used by pretty-printer tests
• detect missing . in method chain in let bindings and statements
• don't ICE on illegal dyn* casts
• explain why a type is not eligible for impl PointerLike
• fix -Z input-stats ordering
• fix const conditions for RPITITs
• fix effect predicates from item bounds in old solver
• fix logical error with what text is considered whitespace
• fix parenthesization of chained comparisons by pretty-printer
• forbid overwriting types in typeck
• foundations of location-sensitive polonius
• handle DropKind::ForLint in coroutines correctly
• handle fndef rendering together with signature rendering
• handle member constraints directly in the mir type checker
• hide = _ as associated constant value inside impl blocks
• make sure we don't lose default struct value when formatting struct
• make sure we handle backwards_incompatible_lint drops appropriately in drop elaboration
• make sure we note ambiguity causes on positive/negative impl conflicts
• move lint_unused_mut into sub-fn
• next-solver: disable unnecessary hack
• pass FnAbi to find_mir_or_eval_fn
• point at lint name instead of whole attr for gated lints
• precedence improvements: closures and jumps
• promote powerpc64le-unknown-linux-musl to tier 2 with host tools
• re-export more rustc_span::symbol things from rustc_span
• reduce the amount of explicit FatalError.raise()
• restrict #[non_exaustive] on structs with default field values
• simplify SwitchInt handling
• support pretty-printing dyn* trait objects
• use PtrMetadata instead of Len in slice drop shims
• use links to edition guide for edition migrations
• win: use POSIX rename semantics for std::fs::rename if available
• mir-opt: a sub-BB of a cleanup BB must also be a cleanup BB in EarlyOtherwiseBranch
• miri: add track_caller to thread spawning methods for better backtraces
• miri: add warning explaining the limitations of the native code mode
• miri: implement blocking unnamed_socket
• miri: implement many-seeds mode directly in the driver
• miri: provide a way to compare benchmark results with baseline
• speed up Parser::expected_tokens
• improve dependency_format a bit
• overhaul token cursors
• fix perf regression in rustdoc after hir attributes
• stabilize #[diagnostic::do_not_recommend]
• core: fix const ptr::swap_nonoverlapping when there are pointers at odd offsets
• add a range argument to vec.extract_if
• optimize is_ascii for str and [u8] further
• implement PointerLike for isize, NonNull, Cell, UnsafeCell, and SyncUnsafeCell
• unimplement PointerLike for trait objects
• hashbrown: add 128-bit SIMD implementation for LoongArch
• compiler-builtins: fix a bug in abs_diff
• cargo: build-std: make Resolve align to what to build
• cargo: cargo-package: add more traces
• cargo: cargo-rustc: stabilize higher precedence trailing flags
• cargo: package: show dirty filepaths relative to git workdir
• cargo: package: use relpath to cwd for vcs dirtiness report
• cargo: add the test cfg as a well known cfg before of compiler change
• cargo: do not hash absolute sysroot path into stdlib crates metadata
• cargo: fixed the error message for a user to open the crate
• rustfmt: fix incorrect strip r# prefix from labels
• clippy: add allow-indexing-slicing-in-tests option
• clippy: do not mark attributes with unknown namespace as useless
• clippy: don't trigger filter_map_identity with an iterator from an empty array
• clippy: use multipart suggestion in unnecessary_to_owned
• rust-analyzer: clear flycheck diagnostics more granularly
• rust-analyzer: fix AsmOption rule in rust.ungram
• rust-analyzer: consider both completion detail fields in to_proto
• rust-analyzer: delay initial flycheck until after build scripts
• rust-analyzer: do not ask the client to resolve for non existing label details
• rust-analyzer: don't trigger paren wrapping typing handler after idents
• rust-analyzer: fix a case where completion was unable to expand a macro
• rust-analyzer: fix empty check diagnostics not marking files as changed
• rust-analyzer: fix flycheck workspace when requested but package was found
• rust-analyzer: fix pretty-printing of @ patterns
• rust-analyzer: properly check if workspace flychecking is allowed
• rust-analyzer: reduce applicability of unnecessary_async assist
• rust-analyzer: remove always! check for file_id in runnables
• rust-analyzer: remove salsa from proc-macro server dep tree
• rust-analyzer: taking a raw ref of a deref is always safe

Rust Compiler Performance Triage

We missed triage last week due to some process issues, so this triage includes two weeks of data. The overall result is positive, due to parser optimizations (#133793), trait solving optimizations (#134501, #132325) and bumping the cc crate (#134505), which improved the performance of C/C++ dependencies of the compiler.

Triage done by @kobzol. Revision range: 1b3fb316..0eca4dd3

Summary:

4 Regressions, 10 Improvements, 12 Mixed; 9 of them in rollups 90 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:

• Add support for use Trait::func
• crates.io: Trusted Publishing Support

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

Rust

• [disposition: merge] Specify the behavior of file!
• [disposition: merge] Stabilize feature(trait_upcasting)
• [disposition: merge] Stabilize derive(CoercePointee)
• [disposition: merge] Stabilize asm_goto feature gate
• [disposition: merge] Tracking Issue for get_many_mut
• [disposition: merge] --nocapture doesn't follow common CLI conventions, making it a stumbling block to people debugging failures
• [disposition: merge] Tracking Issue for sub_ptr (feature ptr_sub_ptr)
• [disposition: merge] From iterator for more tuples
• [disposition: merge] Tracking Issue for const_swap
• [disposition: merge] Tracking issue for const alloc::Layout

Cargo

• No Cargo Tracking Issues or PRs entered Final Comment Period this week.

Language Team

• No Language Team Proposals entered Final Comment Period this week.

Language Reference

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

Unsafe Code Guidelines

• No Unsafe Code Guideline Tracking Issues or PRs entered Final Comment Period this week.

New and Updated RFCs

• [new] RFC: Set CARGO_CHECK environment variable when type checking
• [new] unsized params in traits
• [new] Convert "reassignment of immutable local" and "mutable borrow of immutable local" from a hard error to a deny-by-default lint

Upcoming Events

Rusty Events between 2024-12-25 - 2025-01-22 🦀

Virtual

• 2024-12-26 | Virtual (Charlottesville, VA, US) | Charlottesville Rust Meetup
  • Crafting Interpreters in Rust Collaboratively
• 2025-01-02| Virtual (Berlin, DE) | OpenTechSchool Berlin + Rust Berlin
  • Rust Hack and Learn | Mirror: Rust Hack n Learn Meetup
• 2025-01-04 | Virtual (Kampala, UG) | Rust Circle Kampala
  • Rust Circle Meetup
• 2025-01-06 | Virtual (Tel Aviv-Yafo, IL) | Code Mavens 🦀 - 🐍 - 🐪
  • logger.info(f"Don't Give your {secrets} away") by Tamar Galer (Virtual, English)
• 2025-01-07 | Virtual (Tel Aviv-Yafo, IL) | Code Mavens 🦀 - 🐍 - 🐪
  • Microdosing Rust to your organization with Aviram Hassan (Virtual, English)
• 2025-01-08 | Virtual (Tel Aviv-Yafo, IL) | Code Mavens 🦀 - 🐍 - 🐪
  • BlockMesh Network implemented in Rust with Ohad Dahan (Virtual, English)
• 2025-01-09 | Virtual (Charlottesville, VA, US) | Charlottesville Rust Meetup
  • Crafting Interpreters in Rust Collaboratively
• 2025-01-09 | Miami, FL, US | Rust Miami
  • Rust / Wasm on Serverless and Frontend
• 2025-01-09 | Virtual (Nürnberg, DE) | Rust Nuremberg
  • Rust Nürnberg online
• 2025-01-14 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Second Tuesday
• 2025-01-14 | Virtual (Tel Aviv-Yafo, IL) | Code Mavens 🦀 - 🐍 - 🐪
  • An introduction to WASM in Rust with Márk Tolmács (Virtual, English)
• 2025-01-15 | Virtual (Vancouver, BC, CA) | Vancouver Rust
  • Leptos
• 2025-01-16 | Virtual (Berlin, DE) | OpenTechSchool Berlin + Rust Berlin
  • Rust Hack and Learn | Mirror: Rust Hack n Learn Meetup
• 2025-01-21 | Virtual (Tel Aviv-Yafo, IL) | Rust 🦀 TLV
  • Exploring Rust Enums with Yoni Peleg (Virtual, Hebrew)
• 2025-01-21 | Virtual (Washington, DC, US) | Rust DC
  • Mid-month Rustful
• 2025-01-22 | Virtual (Rotterdam, NL) | Bevy Game Development
  • Bevy Meetup #8

Asia

• 2025-01-12 | Virtual (Tel Aviv-Yafo, IL) | Rust 🦀 TLV
  • In person Rust January 2025 at Abra in Raanana

Europe

• 2025-01-08 | Reading, UK | Reading Rust Workshop
  • Reading Rust Meetup
• 2025-01-09 | Oslo, NO | Rust Oslo
  • Rust Hack'n'Learn at Kampen Bistro
• 2025-01-16 | Karlsruhe, DE | Rust Hack & Learn Karlsruhe
  • Karlsruhe Rust Hack and Learn Meetup bei BlueYonder
• 2025-01-21 | Ghent, BE | Systems Programming Ghent
  • Tech Talks & Dinner: Insights on Systems Programming Side Projects (in Rust) - Leptos (full-stack Rust with webassembly), Karyon (distributed p2p software in Rust), FunDSP (audio synthesis in Rust)
• 2025-01-21 | Leipzig, SN, DE | Rust - Modern Systems Programming in Leipzig
  • Self-Organized Peer-to-Peer Networks using Rust

North America

• 2024-12-26 | Mountain View, CA, US | Hacker Dojo
  • RUST MEETUP at HACKER DOJO
• 2025-01-10 | Boston, MA, US | Boston Rust Meetup
  • Lechmere Rust Lunch, Jan 10
• 2025-01-16 | Nashville, TN, US | Music City Rust Developers
  • Rust Game Development Series 1: Community Introductions
• 2025-01-18 | Boston, MA, US | Boston Rust Meetup
  • Back Bay Rust Lunch, Jan 18
• 2025-01-21 | San Francisco, CA, US | San Francisco Rust Study Group
  • Rust Hacking in Person
• 2025-01-22 | Austin, TX, US | Rust ATX
  • Rust Lunch - Fareground

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

It's only a transmute if it's from the transmute region of std; otherwise it's just sparkling unsafety.

– Josh Triplett on github

Thanks to Josh for the self-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