The Rust Team All Hands in Berlin: a Recap

Apr. 6, 2018 · Aaron Turon

Last week we held an "All Hands" event in Berlin, which drew more than 50 people involved in 15 different Rust Teams or Working Groups, with a majority being volunteer contributors. This was the first such event, and its location reflects the current concentration of team members in Europe. The week was a smashing success which we plan to repeat on at least an annual basis.

The impetus for this get-together was, in part, our ambitious plans to ship Rust, 2018 edition later this year. A week of work-focused facetime was a great way to kick off these efforts!

We've also asked attendees to blog and tweet about their experiences at the #RustAllHands hashtag; the Content Team will be gathering up and summarizing this content as well.

Highlights by team

Below we'll go through the biggest items addressed last week. Note that, as always, reaching consensus in a meeting does not mean any final decision has been made. All major decisions will go through the usual RFC process.

Language design

  • Macros: put together a proposal for the 2018 edition.
    • Stabilize a forward-compatible subset of procedural macros that explicitly opts out of hygiene (by asking all names to be interpreted at the call site).
    • Work out a revised API surface for procedural macros based on what we've learned so far.
    • Stabilize importing macros through normal use statements.
    • Alex Crichton will drive the stabilization process.
  • Extern types: worked through remaining issues for stabilization.
  • Improvements to derive: a proposal to make derive more ergonomic in Rust 2018.
  • Best practices: set up a cross-cutting guidelines effort, encompassing the API guidelines but also including style, lints, and Lang Team recommendations.


  • SIMD: talked through final steps of stabilization; we hope to stabilize in 1.27.
  • Allocators: developed a conservative proposal for stabilizing global allocators; Simon Sapin has set up a new tracking issue.


  • Tool integration: extensive discussion and planning about the needs of compiler clients, composable plugins, and the compiler's new query architecture.
  • Query compilation: a plan for end-to-end query compilation, i.e. fully-incremental compilation.
  • libsyntax: a long-run plan for a revamped libsyntax, shared amongst a variety of tools.
  • Contribution: improved contribution experience for the compiler.



  • Edition planning: determined resources needed for the 2018 edition, what that means for the Rust Bookshelf, and who will be responsible for each.
  • Team blog: “This week in Rust docs” is going to move to a new docs team blog!
  • Doxidize (aka rustdoc2): made initial public release; it's like but for Rust.
  • Intermediate-level docs: contributed to idea generation.


  • Edition planning, especially for the rustfix tool.
  • Clippy lint audit: developed plan for reaching 1.0 on Clippy this year, based on categorizing lints into Correctness, Performance, Style, Complexity, Pedantry, and Nursery categories.
  • Custom test frameworks: reached consensus on most of the details for the RFC
  • IDEs: discussed improvements to code completion, stability improvements, and new features like refactoring and auto-import support.


  • Xargo integration: making a few more platforms tier 1 addresses the immediate need for embedded; otherwise, plan to go the "std-aware Cargo" route late in 2018. Key insight: will entirely obsolete the concept of "targets" in rustup.
  • Rustup integration: with Xargo integration we can simplify rustup; plan to expose new interface via Cargo late in 2018.
  • Custom registries: ready to stabilize.
  • Profiles: the v2 design is clear, and Aleksey Kladov plans to implement.
  • Public dependencies: significantly revised plan to have more conservative ecosystem impact. Aaron Turon will write a blog post.
  • Build system integration: determined two pieces of functionality to implement to decouple the RLS from Cargo.
  • Project templates: developed a minimal design; withoutboats will write an RFC.
  • Custom workflows: designed workflow customization, which is useful for frameworks; Aaron Turon has written a blog post.


  • bors queue: hatched and resourced lots of ideas to reduce the PR queue for Rust 2018.
  • crater: pietroalbini is testing a bot for running crater!
  • Travis log bot: TimNN has written a bot to extract errors from Travis logs

WG: CLI apps

  • WG overview slides.
  • Survey and strategy: dove into survey data and developed strategy from it; posts forthcoming.
  • Distribution: "distribution-friendly" badge on
  • Extensible Cargo install: wrote an RFC on-site!

WG: network services

  • WG overview slides.
  • Launching the WG: determined goals for the WG, including async/await, documentaiton, mid-level HTTP libraries, and the Tower ecosystem. Kickoff announcement coming soon!
  • Async/await: finalized design and stabilization approach for RFCs (blog post and links to RFCs here).

WG: embedded devices

  • WG overview slides
  • Embedded Rust on stable: addressed all known blockers and several mid-priority issues as well.
  • The Embedded Rust book: defined audience and basic outline.

WG: WebAssembly

  • WG overview slides.
  • 2018 edition planning, including scoping the toolchain and book efforts for the release.
  • JS integration: dove into integrating JS callbacks vs Rust functions in wasm-bindgen.
  • Ecosystem integration: wasm-bindgen now works with CommonJS!
  • Code bloat, reducing the footprint of panicking from 44k to 350 bytes.

Unsafe code guidelines

  • Restarted the WG: dug back into two competing approaches ("validity" and "access"-based), substantially iterated on both. Niko Matsakis and Ralf Jung will be writing blog posts about these ideas.
  • Pressing issues: tackled a few near-term decisions that need to be made, including union semantics, Pin semantics, thread::abort and more.

Web site

  • Domain WG sketching: over a couple of sessions, the four domain-centered working groups (listed above) developed some initial sketches of landing pages for each domain.

Rust reach

New working groups

In addition to the work by existing teams, we had critical mass to form two new working groups:

  • Verification: bringing together folks interested in testing, static analysis, and formal verification.
  • Codegen: work to improve the quality of code rustc generates, both in terms of size and runtime performance.

The Verification WG has been formally announced, and the Codegen WG should be announced soon!

General reflections and notes of appreciation

The combination of having a clear goal -- Rust 2018 -- and a solid majority of team member present made the All Hands extremely fun and productive. We strive to keep the Rust community open and inclusive through asynchronous online communication, but it's important to occasionally come together in person. The mix of ambition and kindness at play last week really captured the spirit of the Rust Community.

Of course, an event like this is only possible with a lot of help, and I'd like to thank the co-organizers and Mozilla Berlin office staff:

  • Johann Hofmann
  • Jan-Erik Rediger
  • Florian Gilcher
  • Ashley Williams
  • Martyna Sobczak

as well as all the team leads who organized and led sessions!