Hello and welcome to another issue of This Week in Rust! It's late this week because bors was having some issues which bounced every pull request, and it's no fun writing about nothing.

What's cooking on master?

61 PRs were merged this week.

Breaking Changes

Other changes

  • A dead code warning has been implemented. This is pretty awesome and will do things like warn for test functions that are accidentally never marked #[test] and so are never called. Some bugs in it were also fixed.
  • The benchmark runner now handles slow benchmarks. Previously, it wouldn't run a benchmark that took more than 1ms. Now, it will!
  • The shootout-fasta benchmark has been rewritten. It's about 10x faster, and looks nicer.
  • Stepping through / breaking on function calls no longer goes through the function prelude.
  • The vector move_iter has been made faster.
  • A single #[inline] has made vec::from_elem 20x faster
  • Buffer now has an iterator over its lines. The gotcha is that the newlines are included in the yielded strings.
  • Struct pattern shorthand has been improved by allowing ref/mut, like let Foo { mut x, .. } = some_foo, rather than the previous let Foo { x: mut x, .. } = some_foo.
  • LTO (link time optimization) has been implemented. Rejoice.
  • All landing pads (and thus unwinding!) can now be omitted when doing LTO.
  • std::io::util has been added with:
    • LimitReader that will only read n bytes from another reader
    • NullWriter that ignores everything written to it
    • NullReader that is always EOF
    • ZeroReader which returns all zeroes,
    • MultiWriter which will replicate a written buffer to many writers
    • ChainedReader which reads readers in order to completion
    • TeeReader which will write to a Writer while reading
    • a copy function which copies the full contents of a reader into a writer.
  • Windows application manifests are now embedded, so we don't get special cased.
  • A --dep-info flag has been added which is like -MMD to C compilers.
  • &mut underneath & can now be frozen.
  • PortReader and ChanWriter have been implemented.
  • Some more random distributions have been implemented.
  • We now use LLVM's integrated assembler on Windows.

New contributors

  • Cadence Marseille
  • Edward Z. Yang
  • Erik Price
  • Fabrice Desré
  • Jan Niklas Hasse
  • Richard Diamond


The weekly meeting discussed enum mod, using types to drive inference (rather than attributes like #[no_send] etc), a formal grammar, unwinding, and some various PRs (all mentioned above).

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.

We landed 29 PRs this week.

Notable additions

  • Patrick Walton landed a number of changes to layout to avoid going back to the DOM for properties to make layout's access to the DOM more opaque. He also cleaned up a significant number of regressions and added a huge number of ref tests.
  • Keegan McAllister made content tests work in headless mode in #1382.
  • Daniel Glazman added namespace info to elements in #1358.
  • Daniel Hedlund added support for leading font metrics on Linux #1352.


This week's meeting discussed an upcoming Servo workweek in SF on January 20th. We also discussed the Rust version update and some general team frustration at a large number of regressions lately, primarily caused by the need to disable some of our automated testing due to instability (particularly at shutdown). This week of work saw many of those issues fixed.

Announcements, etc