The Rust team has announced a new version of Rust, 1.34.0. Rust is a programming language that is empowering everyone to build reliable and efficient software.
The largest feature in this release is the introduction of alternative cargo registries. The release also includes support for ? in documentation tests, some improvements for #[attribute(..)], as well as the stabilization of TryFrom.
The compilation unit in Rust is the crate (cashier) unlike the C for example, where it is the file. Each of the crats in a project can use a different edition of the language. For example, you can create a new crate 2015 and use a 2018 crate, which uses new keywords without problems.
With this release, Cargo has support for multiple registries. These registers coexist with crates.io so that you can write software that depends on both crates.io crates and your custom registry. Crate on crates.io can not however depend on external registers.
Support in fn main () and # [test] has been implemented in several versions. However, support in documentation tests was limited to those with an explicit () hand. In this version, the full support for? in doctests has been added.
Source : Rust Blog