Hello 2016! We’re happy to announce the first Rust release of the year, 1.6. Rust is a systems programming language focused on safety, speed, and concurrency.

As always, you can install Rust 1.6 from the appropriate page on our website, and check out the detailed release notes for 1.6 on GitHub. About 1100 patches were landed in this release.

What's in 1.6 stable

This release contains a number of small refinements, one major feature, and a change to Crates.io.

libcore stabilization

The largest new feature in 1.6 is that libcore is now stable! Rust’s standard library is two-tiered: there’s a small core library, libcore , and the full standard library, libstd , that builds on top of it. libcore is completely platform agnostic, and requires only a handful of external symbols to be defined. Rust’s libstd builds on top of libcore , adding support for memory allocation, I/O, and concurrency. Applications using Rust in the embedded space, as well as those writing operating systems, often eschew libstd , using only libcore .

libcore being stabilized is a major step towards being able to write the lowest levels of software using stable Rust. There’s still future work to be done, however. This will allow for a library ecosystem to develop around libcore , but applications are not fully supported yet. Expect to hear more about this in future release notes.

Library stabilizations

About 30 library functions and methods are now stable in 1.6. Notable improvements include:

The drain() family of functions on collections. These methods let you move elements out of a collection while allowing them to retain their backing memory, reducing allocation in certain situations.

A number of implementations of From for converting between standard library types, mainly between various integral and floating-point types.

Finally, Vec::extend_from_slice() , which was previously known as push_all() . This method has a significantly faster implementation than the more general extend() .

See the detailed release notes for more.

Crates.io disallows wildcards

If you maintain a crate on Crates.io, you might have seen a warning: newly uploaded crates are no longer allowed to use a wildcard when describing their dependencies. In other words, this is not allowed:

[dependencies] regex = "*"

Instead, you must actually specify a specific version or range of versions, using one of the semver crate’s various options: ^ , ~ , or = .

A wildcard dependency means that you work with any possible version of your dependency. This is highly unlikely to be true, and causes unnecessary breakage in the ecosystem. We’ve been advertising this change as a warning for some time; now it’s time to turn it into an error.

Contributors to 1.6

We had 132 individuals contribute to 1.6. Thank you so much!