Hello and welcome to another issue of This Week in Rust! Rust is a systems language pursuing the trifecta: safe, concurrent, and fast. This is a weekly summary of its progress and community. Want something mentioned? Send me an email! Want to get involved? We love contributions.

There were a surprising number of breaking changes this week. The libextra dissolution continues. Condition removal and the IO error overhaul also landed. rustpkg was also removed, and rustc's CLI interface has changed. Additionally, Rust gained another full-time developer! A big hello to Nick Cameron, I look forward to seeing his work.

It was also discovered that we closed the second largest number of issues of any repository on GitHub! We trailed behind homebrew, which is almost cheating, because they use it to track issues on over five thousand packages. Good job everyone!

What's cooking on master?

72 pull requests were merged this week.

Breaking Changes

Some intrinsics have been moved into std::mem, in preparations of the intrinsics no longer being publically exposed.
A soundness regression has been fixed.
char now has range asserts. This may cause invalid uses of char (using invalid values) to break.
The various traits in std::fmt now use &self, rather than a separate parameter with an argument of type &Self.
@self and @Trait (managed trait objects) have been removed.
rustpkg has been removed.
std::fmt::Default has been renamed to Show.
IO errors have been completely overhauled, and no longer use conditions. Alex wrote an email to the mailing list summarizing the changes. Especially take note of the if_ok! macro.
Conditions have been removed entirely. A detailed post-mortem is available on the pull request.
rustc has seen some work on its interface. The output flags have been unified, replacing -c, --emit-llvm, -S, --dylib, --rlib, etc with two arguments: --emit and --crate-type. There is another PR in the queue that replaces a bunch of miscellaneous flags behind -C. It will likely land shortly, and is something to be aware of.
NonCopyable has been renamed to NoPod to be consistent with the rest of the "marker types".
reserve naming has been shuffled around slightly. reserve becomes reserve_exact and reserve_at_least becomes reserve.
SendStr has been removed in favor of a MaybeOwned type.

As part of the libextra dissolution, the following crates have been introduced:

libcollections, which has inherited Bitv, BTree, Deque, DList, List, LruCache, PriorityQueue, RingBuf, SmallIntMap, TreeMap, and TreeSet.
libgetopts, which has inherited extra::getopts. Additionally, getopts::groups is now the only interface. It has been moved up a level, into just getopts, and the old functions have been removed.
libserialize, which has inherited extra::serialize and extra::ebml.
libuuid, which has inherited extra::uuid.
libsemver, which has inherited extra::semver.
libterm, which has inherited extra::term and extra::terminfo.

All crates are still documented, and there is a list with links at http://static.rust-lang.org/doc/master/index.html.

Other Changes

A black_box function has been added to extra::test, and the iter method on BenchHarness can now return values. As documented (generated version), these exist to make sure that LLVM will not optimize out benchmarks.
A fourcc! syntax extension has been added.
A unimplemented! macro has been added, used much the same as unreachable!().
The [runtime libraries have gained examples, and libgreen now has an explanation of how it is structured at a high level, specifically where concurrency and parallelism come from.
A from_utf8_lossy function has been added that replaces invalid codepoints with the unicode replacement character (�).
Network streams are now cloneable. This allows for multiple tasks reading/writing a TcpStream.
A copy-on-write Arc container has been added to libextra, though it's now in libcontainers.
SIMD types are now allowed in generics.
A new mutex type that plays well with the various runtimes has been implemented. It is in the same ballpark as native, pthread mutexes.

New Contributors

Arcterus
Cole Mickens
Colin Sherratt
HeroesGrave
Ivan Enderlin
James Deng
João Souls
Marek Šuppa
Q.P.Liu
Yuri Kunde Schlesner

Weekly Meeting

The weekly meeting discussed adding a libprim, operator overloading, and the 1.0 goals for LLVM.

Meetups

There will be a meetup in Paris, on February 25, from 18:30 to 23:30.
Bay Area Rust will be meeting February 25, at 19:00 in San Francisco. David Renshaw will be talking about Cap' Proto, Steven Fackler will be talking about exportable macros, and Kevin Cantu about testing.

This Week in Servo

Servo is a web browser engine written in Rust and is one of the primary test cases for the Rust language.

This week, we landed 14 PRs, but there are a substantial number of very close pending PRs that add major layout features to Servo (e.g., lists markers, tables, initial pseudo-class and pseudo-element support).

Notable additions

Bruno Abinader continued with his great DOM additions in #1634 and #1622 and #1604
Patrick Kim fixed borders on inline boxes in #1577 and landed position:relative support in #1613
Patrick Walton further improved layout performance in #1630 and #1615
Adrien Bustany fixed insertBefore in #1621
Lars Bergstrom landed reftest stabilization fixes in #1623 - we are almost ready to gate landing commits on content and ref tests passing on Linux, once we get more fonts installed on our Linux buildbots

New contributors

Adrien Bustany (abustany)

Meetings

In this week's meeting, we mainly discussed display list construction with respect to layering and stacking contexts.

Josh Matthews' talk on Servo at FOSDEM is available here.