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. If you find any errors in this week's issue, please submit a PR.

Updates from Rust Community




Project/Tooling Updates


Rust Walkthroughs



Crate of the Week

This week's crate is Darkbird, a mnesia-inspired high concurrency, real time, in-memory storage library.

Thanks to DanyalMh for the self-suggestion!

Please submit your suggestions and votes for next week!

Call for Participation

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!

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

Updates from the Rust Project

378 pull requests were merged in the last week

Rust Compiler Performance Triage

Largely a win for compiler performance with 100 test cases in real-world crates showing some sort of change in performance with an average 1% improvement. These wins were a combination of many different changes including how doc(hidden) gets more efficiently encoded in metadata, some optimizations in the borrow checker, and simplification of the output from derive(Debug) for fieldless enums.

Triage done by @rylev. Revision range: 1f72129f..c8e6a9e8


(instructions:u) mean range count
Regressions ❌
0.4% [0.2%, 0.7%] 19
Regressions ❌
0.9% [0.2%, 1.5%] 34
Improvements ✅
-1.3% [-17.2%, -0.2%] 81
Improvements ✅
-2.1% [-7.1%, -0.2%] 64
All ❌✅ (primary) -1.0% [-17.2%, 0.7%] 100

2 Regressions, 5 Improvements, 3 Mixed; 1 of them in rollups 34 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.


  • No RFCs entered Final Comment Period this week.

Tracking Issues & PRs

New and Updated RFCs

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 2023-01-25 - 2023-02-22 🦀




North America

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.


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

Quote of the Week

Rust has demonstrated that you using a type system as a vehicle for separation logic works, even in imperative languages, and it's nothing as arcane as those immutable functional predecessors would suggest. It did this by making sure the language defines a type system that helps you, by making sure core properties of soundness can be expressed in it.

  • soundness requirement for memory access: lifetimes
  • soundness requirements for references with value semantics: > &/&mut _
  • soundness requirements for resources: Copy and Drop
  • making sure your logic is monotic: traits instead of inheritance, lack of specialization (yes, that's a feature).
  • (notably missing: no dependent types; apparently not 'necessary' but I'm sure it could be useful; however, research is heavily ongoing; caution is good)

This allows the standard library to encode all of its relevant requirements as types. And doing this everywhere is its soundness property: safe functions have no requirements beyond the sum of its parameter type, unsafe functions can. Nothing new or special there, nothing that makes Rust's notion of soundness special.

Basing your mathematical reasoning on separation logic makes soundness reviews local instead of requiring whole program analysis. This is what makes it practical. It did this pretty successfully and principled, but did no single truly revolutionary thing. It's a sum of good bits from the last decade of type system research. That's probably why people refer to it as 'the soundness definition', it's just a very poignant way to say: "we learned that a practical type systems works as a proof checker".

HeroicKatora on /r/cpp

Thanks to Stephan Sokolow 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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