Hello and welcome to another issue of This Week in Rust! Rust is a systems language pursuing the trifecta: safety, concurrency, and speed. 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

Official

• [Inside] Rustdoc performance improvements
• [Inside] Changes to the Rustdoc team

Newsletters

• This Month in Rust GameDev #17 - December 2020

Project/Tooling Updates

• IntelliJ Rust Changelog #139
• rust-analyzer Changelog #60
• Knurling-rs Changelog #13
• This week in Ballista #1
• Deno in 2020
• async-std v1.9.0
• [video] Penrose 0.2.0 Overview

Observations/Thoughts

• Cryptoxide perf (SHA2 / Blake2)
• About variadics in Rust
• Rust in Production: 1Password
• Unconditional loops are unconditionally awesome
• Rust is a hard way to make a web API
• Writing a better Line Iterator in Rust
• Implementing cross-process Sanakirja locks
• future::join and const-eval
• I used Rust in production for 6 months! Here's my feedback
• [video] Learning Rust with "Too Many Linked Lists" (Episode 2) - Pop & Drop
• [video] std::process::exit is evil - a Rust bug fixing story

Rust Walkthroughs

• Polishing Rust: Boxing and Unboxing Results
• Efficient custom shapes in QtQuick with Rust
• Scientific Computing in Rust
• Rust GUI: Introduction a.k.a. the state of Rust GUI libraries (as of January 2021)
• How to Fetch a Web API with Rust 🦀
• Replacing FastAPI with Rust: Part 4 - A Solution
• Getting started with Rust and Redis
• How To Write A REST Client In Rust
• [video] Rust live coding - Tower deep dive

Miscellaneous

• Rust/WebAssembly on AWS Lambda@Edge
• [video] (Live Coding) Zola, a Static Site Generator. Migrating my blog & reviewing Zola's source code.

Crate of the Week

This week's crate is dotenv-linter, a lightning fast linter for .env files.

Thanks to Grachev Mikhail for the suggestion!

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.

• magic-wormhole/magic-wormhole.rs

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

Updates from Rust Core

391 pull requests were merged in the last week

• use correct ABI for wasm32 by default
• improve diagnostics when closure doesn't meet trait bound
• enhance type inference errors involving the ? operator
• explain method-call move errors in loops
• make CTFE able to check for undefined behavior
• split a func into cold/hot parts, reducing rustc binary size
• suggest _ and .. if a pattern has too few fields
• suggest async {} for async || {}
• do not suggest invalid code in pattern with loop
• add allow-by-default lint on implicit ABI in extern function pointers and items
• reintroduce hir::ExprKind::If
• remove redundant def_id lookups
• serialize incr comp structures to file via fixed-size buffer
• turn type inhabitedness into a query to fix exhaustive_patterns perf
• box Item::Attributes
• resolve: simplify collection of traits in scope
• use Once instead of Mutex to manage capture resolution
• consistently avoid constructing optimized MIR when not doing codegen
• add benchmark and fast path for BufReader::read_exact
• add MaybeUninit method array_assume_init
• change BinaryHeap::append rebuild heuristic
• implement ptr::write without dedicated intrinsic
• introduce {Ref, RefMut}::try_map for optional projections in RefCell
• re-stabilize Weak::as_ptr and friends for unsized T
• add Iterator::intersperse_with
• TrustedRandomAaccess specialization composes incorrectly for nested iter::Zips
• remove unreachable panics from VecDeque::{front/back}(_mut)
• add NonZeroUn::is_power_of_two
• stabilize split_inclusive
• stabilize the poll_map feature
• add as_rchunks (and friends) to slices
• hashbrown: hide allocator details and default to Global
• hashbrown: export AllocError as well as Allocator
• regex: implement regex::Replacer for String, &String, Cow<'a, str>, &Cow<'a, str>
• futures: fix type-inference in sink::unfold() by specifying more of its types
• clippy: roadmap for 2021

Rust Compiler Performance Triage

• 2020-01-12: 1 Regressions, 2 Improvements, 3 Mixed Overall, a positive albeit quiet week. The largest change came from the incremental compilation working group which delivered large gains in performance caused by changes in how inlining is handled in debug mode. Unfortunately, these changes may be reversed due to concerns

Triage done by @rylev.

See the full report for more.

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

• Allow "artifact dependencies" on bin, cdylib, and staticlib crates
• RFC: Pointer metadata & VTable

Tracking Issues & PRs

• [disposition: merge] Remove requirement that forces symmetric and transitive PartialEq impls to exist
• [disposition: merge] Stabilize core::slice::fill_with
• [disposition: merge] Stabilize unsigned_abs
• [disposition: merge] Add Box::downcast() for dyn Any + Send + Sync
• [disposition: merge] Stabilize by-value [T; N] iterator core::array::IntoIter
• [disposition: merge] Implement missing AsMut<str> for str
• [disposition: merge] stabilise cargo test -- --include-ignored
• [disposition: merge] rustc: Stabilize -Zrun-dsymutil as -Csplit-debuginfo
• [disposition: merge] Stabilize Arc::{increment,decrement}_strong_count
• [disposition: merge] Implement io::Seek for io::Empty
• [disposition: merge] Stabilize Seek::stream_position (feature seek_convenience)

New RFCs

No new RFCs were proposed this week.

Upcoming Events

Online

• January 21, Berlin, DE - Rust Hack and Learn - Berline.rs
• January 26, Dallas, TX, US - Last Tuesay - Dallas Rust
• January 27, New York, NY, US - Snapshot testing in Rust with K9 with Aaron Abramov - Rust NYC
• February 2, Buffalo, NY, US - Buffalo Rust User Group - Buffalo Rust Meetup

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.

Rust Jobs

• Rust Developer - Full Stack at HUM Systems (Berlin, DE)
• Multiple Roles at Ockam (Remote)
• Lead Developer Embedded Rust at Tweede Golf (Nijmegen, NL)
• Junior Rust Engineer at Bolt Labs (Remote, USA only)

Tweet us at @ThisWeekInRust to get your job offers listed here!

Quote of the Week

Why do I use the letter ‘o’ for my generic closure param name? [...] I recently realized that since Rust uses pipes to enclose a param block, using ‘o’ makes the block look like a TIE fighter. I am not a terribly serious person.

– Tim Keating on medium

Thanks to Edoardo Morandi for the suggestion.

Please submit quotes and vote for next week!

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

Discuss on r/rust