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

News & Blog Posts

2017 State of Rust Survey.
The Rust Libz Blitz. Raising a solid core of the Rust crate ecosystem to a consistent level of completeness and quality as part of Rust language 2017 ergonomic improvements initiative.
David Tolnay (of Serde fame) joins the Rust libs team.
How I broke Rust's package manager for all Windows users.
The pain of real linear types in Rust.
The balance between cost, usability, and soundness in C bindings, and Rust-SDL2's release.
gnome-class: Integrating Rust and the GNOME object system.
Fearless concurrency in your microcontroller.
Rust on Teensy part 3: Improving safety. PJRC Teensy is a USB-based microcontroller development system.
Ownership controls mutability.
Gtk-rs: New crates.io versions available and API improvements.
Rust makes it into a AAA video game!... Sort of.
This week in Rust docs 55.
This week in Servo 101.

Crate of the Week

This week's crate of the week is remove_dir_all, a safe, reliable implementation of remove_dir_all for Windows. Thanks to brson 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.

Crate evaluation for 2017-05-16: log. People are needed to help fill out the log crate evaluation, write cookbook recipes for the log crate, and generally offer their opinions.
cross: OpenSSL missing for i686-musl. cross allows you to do "zero setup" cross compilation and "cross testing" of Rust crates.
cross: libmusl with static OpenSSL.
[easy] url: Implement Debug for many types. Servo's url is a URL parser library for Rust.
url: Implement Default for ParseOptions and ParseOptions::new.
[easy] url: Modify docs to put error conditions into Errors sections.
url: Better documentation for quirks module.
[easy] url: Improvements to Origin docs.
[easy] url: Add examples to Url methods.
[easy] url: Add examples to ParseOptions.
url: Modify define_encode_set to support private definitions.
url: Document the percent_encoding module.
[easy] rust-cookbook: Switch error handling setup to quick_main! macro from error-chain. Rust Cookbook is a collection of simple examples that demonstrate good practices to accomplish common programming tasks.
memmap: Overhaul API. memmap-rs is a Rust library for cross-platform memory-mapped file IO.
memmap: Document error conditions for fallible methods in a separate "Errors" section.
memmap: Add examples to methods.
memmap: Expand crate-level documentation.
[easy] tokei: AutoHotKey support. Tokei is a program that displays statistics about your code.

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

Updates from Rust Core

122 pull requests were merged in the last week.

MutexGuard<T> is now only Sync if T is (breaking change, fixes unsoundness)
far-ranging MIR pipeline changes (also adds "stealing" as a more violent form of borrowing)
fix arm-linux-androideabi
fix Windows' ULONG_PTR type on Windows 32 bit systems
Rust documenters can now write '##' to show # in rustdoc output
Windows doctests no longer deadlock
reworking NonZero, Shared and Unique (so they can be stabilized – fingers crossed)
core::sync::atomic::hint_core_should_pause() for optimized atomic spin loops
various LLVM backports
variance refactoring, no more pub map
on-demand-ify region mapping
remove ast-ty-to-ty cache
delete no longer used syntax features
remove unused TyCtxt fields
suggest ! for bitwise negation when encountering ~ prefix (ease transition from C)
point to fields that make type recursive
lint against and remove anonymous parameters (deprecated soon)
remove obsolete --disable-elf-tls switch
forbid -Z on stable and beta
the rust build process can now generate XZ-compressed tarballs
rust-installer will use available xz or 7z
cargo bench --all

New Contributors

acdenisSK
Bobby Holley
Charlie Sheridan
Jing Zhao
Joshua Sheard
Masaki Hara
Migi
Raphaël Huchet
Tommy Ip

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. This week's FCPs are:

[disposition: close] Allow any Displayable type for expect.
[disposition: merge] Expand and stabilize impl Trait.
[disposition: merge] Specify #[repr(transparent)].
[disposition: merge] Extend entry API to work on borrowed keys.
[disposition: merge] Remove static bound from type_id.
[disposition: merge] extend ? to operate over other types.

New RFCs

Style RFCs

Style RFCs are part of the process for deciding on style guidelines for the Rust community and defaults for Rustfmt. The process is similar to the RFC process, but we try to reach rough consensus on issues (including a final comment period) before progressing to PRs. Just like the RFC process, all users are welcome to comment and submit RFCs. If you want to help decide what Rust code should look like, come get involved!

We're making good progress and the style is coming together. If you want to see the style in practice, check out our example or use the Integer32 Playground and select 'Proposed RFC' from the 'Format' menu. Be aware that implementation is work in progress.

PRs: