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? Tweet us at @ThisWeekInRust 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 cargo-llvm-cov, a cargo subcommand for LLVM-based code coverage.

Thanks to Jacob Pratt for the suggestion.

Please submit your suggestions and votes for next week!

Call for Participation

Always wanted to contribute to open-source projects but didn't 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.

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

Updates from Rust Core

296 pull requests were merged in the last week

Rust Compiler Performance Triage

A very busy week with relatively even amounts of regressions and improvements (albeit with improvements outweighing regressions). The largest win was the use of profile-guided optimization (PGO) builds on x86_64 linux builds which brings fairly large improvements in real-world crates. There were 2 regressions that caused fairly large (~3.5%) regressions in real-world crates which need to be investigated.

Triage done by @rylev. Revision range: 33fdb..fe379

5 Regressions, 4 Improvements, 5 Mixed; 0 of them in rollups 56 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.


Tracking Issues & PRs

New RFCs

No new RFCs were proposed this week.

Upcoming Events


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Rust Jobs


Polar Sync

Subspace Labs




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Quote of the Week

Anyway: the standard library docs say "check the nomicon"
then the nomicon says "here is some advice and ultimately we don't know, maybe check UCG"
then UCG says "ultimately we don't know it's probably like this but there's no RFC yet"
then Ralf says "probably it should be allowed if the layout matches".

Lokathor on the Rust Zulip

Thanks to Riccardo D'Ambrosio for the suggestion!

Please submit quotes and vote for next week!

This Week in Rust is edited by: nellshamrell, llogiq, and cdmistman.

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