Rust Language

What’s new in Rust 1.43

Rust was designed to make it easy to develop fast and safe system-level software; here’s what’s new

The unique approach of the Rust programming language results in better code with fewer compromises than C, C++, Go, and the other languages you probably use. It also gets updated regularly, often every month.

Where to download the latest Rust version

If you already have a previous version of Rust installed via rustup, you can access the latest version via the following command:

$ rustup update stable

The new features in Rust 1.43.1

This point release was introduced May 7, 2020, to address two regressions introduced in the 1.43.0 stable release. It also updates the OpenSSL version used by the Cargo package manager. Features include:

  • Rust 1.27 introduced support for detecting x86 CPU features in the standard library, via the is_x86_feature_detected macro. Because of an internal refactoring, Rust 1.43.0 prevented detection of features that cannot be used on stable yet, even though detecting them previously was allowed. Version 1.43.1 fixes this regression.
  • A fix is offered for broken cargo package –list command. Rust 1.43 broke support for listing files included in packages published with Cargo, when executed inside a workspace with path dependencies or unpublished versions.
  • OpenSSL, a Cargo dependency, has been updated to 1.1.1g. OpenSSL had released a security advisory but the Rust team was not able to include the fix in time for Rust 1.43.0. The team has no evidence the vulnerability could compromise Cargo users’ security.

The new features in Rust 1.43.0

Announced April 23, 2020, Rust 1.43.0 was considered a fairly minor release, with no major features introduced. Changes include:

  • Developers can use item fragments to interpolate items into the body of trait, impl, and extern blocks.
  • The type inference around primitives, references, and binary operations was improved.
  • To help integration testing, Cargo will set some new environment variables for tests to find executables.
  • In the Rust library, developers can use associated constants on floats and integers directly without having to import the module. Also, there is a new primitive module that re-exports Rust primitive types, which is useful when writing a macro and developers want to ensure types are not shadowed.
  • Several APIs in the library were stabilized: Once::is_completed, f32::LOG10_2, f32::LOG2_10, f32::LOG10_2, f64::LOG10_2, f64::LOG2_10, and iter::once_with.

The new features in Rust 1.41

The new features in Rust 1.38

Rust 1.38, released in September 2019, contains the following new features and improvements:

  • The Cargo package manager will take advantage of pipelined compilation automatically with Rust 1.38. With pipelined compilation, the compiler does not need dependencies fully built when compiling a crate. All that is needed is their metadata, such as the list of types of dependencies. Metadata is produced early in the compilation process. Some tests have shown compilation speed increases of 10 to 20 percent for optimized, clean builds of some crate graphs. 
  • Linting of some incorrect uses of mem::{unitialized, zeroed}. With this release, the rustc compiler will provide a lint for a narrow class of incorrect initializations using mem::uninitialized or mem::zeroed.
  • Extension of the #[deprecated] attribute to macros. This attribute has allowed crate authors to notify users that an item of their crate is to be deprecated and removed in a future release.
  • Developers can use std::any::type_name to get the name of a type.
  • Stabilization of a number of functions including <*const T>::cast and <*mutT>::cast.

The new features in Rust 1.37

Rust 1.37, released in August 2019, has the following new features and improvements:

  • An ability to refer to enum variants through type. Developers also can refer to enum variants with Self::Variant.
  • The cargo vendor command, previously a separate crate, is now built in to the language. The command fetches project dependencies, unpacks them into the vendordirectory, and displays the configuration snippet needed to use the vendored code during builds.
  • The rustc compiler supports profile-guided optimization, an optimizing technique for ahead-of-time compilers, via -C profile-generate and -C profile-use.
  • Developers can create unnamed const items.

The new features in Rust 1.36

Version 1.36 of the Rust systems programming language was released in July 2019. Rust 1.36 includes the following new features and enhancements:

  • The Future trait, used for declaring asynchronous work, is now stable. Asynchronous operations in Rust have been coming together in bits and pieces for several versions now, with async and await being the last important remaining pieces.
  • The alloc crate, used for managing memory, is now stable. This crate collects all of the pieces of Rust’s standard library that depend on a global memory allocation mechanism, such as Vec<T>. This way, crates that don’t use the standard library can still make use of the allocator by importing alloc separately—useful for environments where you want code sizes to be as lean as possible.
  • A new type, MaybeUninit<T>, allows you to define objects that may consist of uninitialized memory, such as a lazily allocated array. Rust’s previous mechanism for doing this was a function, mem::uninitialized, that posed many hazards in casual use. MaybeUninit<T> provides a safer way to do this that uses the constraints of Rust’s type system.
  • Non-lexical lifetimes, a feature for recent editions of Rust, has been backported to earlier editions. Non-lexical lifetimes make Rust’s borrow-checking mechanism less difficult to work with (in essence, letting you write a broader range of programs that are still valid Rust), and better able to catch problems that the borrow checker missed.

Other improvements:

  • A new implementation for the HashMap<K, V> type that runs faster and uses less memory.
  • Cargo can now run entirely offline if needed.

The new features in Rust 1.35

Version 1.35, released in May 2019, offers the following:

  • Implementation of the FnOnce, FnMut, and Fn closure traits for Box<dyn FnOnce>, Box<dyn FnMut>, and Box<dyn Fn>.
  • The dbg! macro introduced in Rust 1.32 now can be called without arguments.
  • Fn* closure traits now are implemented for Box<dyn Fn*>.
  • Stabilizations of the standard library.
  • Clippy, providing a collection of lints to catch common mistakes, added a lint, drop_bounds, which is triggered when adding a bound T: Drop to a generic function.
  • A ptr::hash function has been introduced, so developers can avoid hashing the pointed-to value of a reference and instead hash the address.
  • The value of a RefCell can be replaced through a closure. Developers can more ergonomically map and replace the current value of the cell and retrieve the old value.
  • Developers now can easily check whether a value exists in a range.
  • A number of changes have been made to the Cargo, such as the addition of a rustc-cdylib-link-arg key for build scripts to specify linker arguments for cdylib crates.

The new features in Rust 1.34

Released April 2019, Rust 1.34 includes the following new and changed features:

  • Cargo, the project and package management system for Rus, now works with registries other than the default (Crates.io), including self-hosted registries. Note that any Crates hosted on Crates.io can only depend on Crates also in Crates.io.
  • The ? operator, used for unpacking errors and valid values from Result types, can now be used in documentation tests. This makes it possible to write more fully fleshed out test examples alongside the code being documented.
  • Custom attributes can now accept arbitrary token streams. This allows custom attributes in procedural macros to be more succinct and use more idiomatic Rust code.
  • The TryFrom and TryInto traits can now allow type conversions that might allow failure.
  • Many library and API stabilizations have been added, such as support for a wider range of atomic integer types (which can be shared safely between threads).

The new features in Rust 1.33

Rust 1.33 debuted in late February 2019 with the following new features:

  • A new language concept, called pinning, is now available. Pinning allows the developer to specify an object in memory that is guaranteed not to move. The Pin type and the Unpin marker trait are used to implement this.
  • The const fn declaration, used to declare functions that can be called in constant expressions at compile time, has been expanded to cover many more use cases, such as let bindings (including mutable ones), assignment expressions, and expression statements. In short, the const fn declaration makes more of the language available in a compile-time context.
  • The use n as _ syntax allows you to import the impl of a trait without polluting the namespace it is imported into.
  • Many library elements have been stabilized by being made const.

The new features in Rust 1.32

The 1.32 version of Rust, released in January 2019, includes the following changes:

  • The dbg macro. Inserting dbg!() into a Rust application prints any println!-formattable expression to stderr, with a minimal amount of boilerplate. Inserting print statements as an aid to debugging is an old-school technique, but a reliable fallback when you just need to know the state of a variable at a given point in time.
  • The jemalloc memory allocator is no longer the default. Rust applications now use the system’s own memory allocator as the default, with jemalloc available via the jemallocator crate. Using the system allocator reduces the size of Rust binaries by about 300 KB, and makes the default behavior for Rust apps across platforms more consistent. (Rust apps built on Microsoft Windows have used the system allocator by default for some time now.)
  • Macros now have the ability to perform matching against all types of literals—strings, numerics, and char literals. This makes it easier to write macros that accept literals as parameters.
  • More refinements to the way module imports work, further reducing the amount of boilerplate needed for trivial apps.

The new features in Rust 1.31

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