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<ol class="chapter"><li class="expanded affix "><a href="title-page.html">The Rust Programming Language</a></li><li class="expanded affix "><a href="foreword.html">Foreword</a></li><li class="expanded affix "><a href="ch00-00-introduction.html">Introduction</a></li><li class="expanded "><a href="ch01-00-getting-started.html"><strong aria-hidden="true">1.</strong> Getting Started</a></li><li><ol class="section"><li class="expanded "><a href="ch01-01-installation.html"><strong aria-hidden="true">1.1.</strong> Installation</a></li><li class="expanded "><a href="ch01-02-hello-world.html"><strong aria-hidden="true">1.2.</strong> Hello, World!</a></li><li class="expanded "><a href="ch01-03-hello-cargo.html"><strong aria-hidden="true">1.3.</strong> Hello, Cargo!</a></li></ol></li><li class="expanded "><a href="ch02-00-guessing-game-tutorial.html"><strong aria-hidden="true">2.</strong> Programming a Guessing Game</a></li><li class="expanded "><a href="ch03-00-common-programming-concepts.html"><strong aria-hidden="true">3.</strong> Common Programming Concepts</a></li><li><ol class="section"><li class="expanded "><a href="ch03-01-variables-and-mutability.html"><strong aria-hidden="true">3.1.</strong> Variables and Mutability</a></li><li class="expanded "><a href="ch03-02-data-types.html"><strong aria-hidden="true">3.2.</strong> Data Types</a></li><li class="expanded "><a href="ch03-03-how-functions-work.html"><strong aria-hidden="true">3.3.</strong> Functions</a></li><li class="expanded "><a href="ch03-04-comments.html"><strong aria-hidden="true">3.4.</strong> Comments</a></li><li class="expanded "><a href="ch03-05-control-flow.html"><strong aria-hidden="true">3.5.</strong> Control Flow</a></li></ol></li><li class="expanded "><a href="ch04-00-understanding-ownership.html"><strong aria-hidden="true">4.</strong> Understanding Ownership</a></li><li><ol class="section"><li class="expanded "><a href="ch04-01-what-is-ownership.html"><strong aria-hidden="true">4.1.</strong> What is Ownership?</a></li><li class="expanded "><a href="ch04-02-references-and-borrowing.html"><strong aria-hidden="true">4.2.</strong> References and Borrowing</a></li><li class="expanded "><a href="ch04-03-slices.html"><strong aria-hidden="true">4.3.</strong> The Slice Type</a></li></ol></li><li class="expanded "><a href="ch05-00-structs.html"><strong aria-hidden="true">5.</strong> Using Structs to Structure Related Data</a></li><li><ol class="section"><li class="expanded "><a href="ch05-01-defining-structs.html"><strong aria-hidden="true">5.1.</strong> Defining and Instantiating Structs</a></li><li class="expanded "><a href="ch05-02-example-structs.html"><strong aria-hidden="true">5.2.</strong> An Example Program Using Structs</a></li><li class="expanded "><a href="ch05-03-method-syntax.html"><strong aria-hidden="true">5.3.</strong> Method Syntax</a></li></ol></li><li class="expanded "><a href="ch06-00-enums.html"><strong aria-hidden="true">6.</strong> Enums and Pattern Matching</a></li><li><ol class="section"><li class="expanded "><a href="ch06-01-defining-an-enum.html"><strong aria-hidden="true">6.1.</strong> Defining an Enum</a></li><li class="expanded "><a href="ch06-02-match.html"><strong aria-hidden="true">6.2.</strong> The match Control Flow Operator</a></li><li class="expanded "><a href="ch06-03-if-let.html"><strong aria-hidden="true">6.3.</strong> Concise Control Flow with if let</a></li></ol></li><li class="expanded "><a href="ch07-00-managing-growing-projects-with-packages-crates-and-modules.html"><strong aria-hidden="true">7.</strong> Managing Growing Projects with Packages, Crates, and Modules</a></li><li><ol class="section"><li class="expanded "><a href="ch07-01-packages-and-crates.html"><strong aria-hidden="true">7.1.</strong> Packages and Crates</a></li><li class="expanded "><a href="ch07-02-defining-modules-to-control-scope-and-privacy.html"><strong aria-hidden="true">7.2.</strong> Defining Modules to Control Scope and Privacy</a></li><li class="expanded "><a href="ch07-03-paths-for-referring-to-an-item-in-the-module-tree.html"><strong aria-hidden="true">7.3.</strong> Paths for Referring to an Item in the Module Tree</a></li><li class="expanded "><a href="ch07-04-bringing-paths-into-scope-with-the-use-keyword.html"><strong aria-hidden="true">7.4.</strong> Bringing Paths Into Scope with the use Keyword</a></li><li class="expanded "><a href="ch07-05-separating-modules-into-different-files.html"><strong aria-hidden="true">7.5.</strong> Separating Modules into Different Files</a></li></ol></li><li class="expanded "><a href="ch08-00-common-collections.html"><strong aria-hidden="true">8.</strong> Common Collections</a></li><li><ol class="section"><li class="expanded "><a href="ch08-01-vectors.html"><strong aria-hidden="true">8.1.</strong> Storing Lists of Values with Vectors</a></li><li class="expanded "><a href="ch08-02-strings.html"><strong aria-hidden="true">8.2.</strong> Storing UTF-8 Encoded Text with Strings</a></li><li class="expanded "><a href="ch08-03-hash-maps.html"><strong aria-hidden="true">8.3.</strong> Storing Keys with Associated Values in Hash Maps</a></li></ol></li><li class="expanded "><a href="ch09-00-error-handling.html"><strong aria-hidden="true">9.</strong> Error Handling</a></li><li><ol class="section"><li class="expanded "><a href="ch09-01-unrecoverable-errors-with-panic.html"><strong aria-hidden="true">9.1.</strong> Unrecoverable Errors with panic!</a></li><li class="expanded "><a href="ch09-02-recoverable-errors-with-result.html"><strong aria-hidden="true">9.2.</strong> Recoverable Errors with Result</a></li><li class="expanded "><a href="ch09-03-to-panic-or-not-to-panic.html"><strong aria-hidden="true">9.3.</strong> To panic! or Not To panic!</a></li></ol></li><li class="expanded "><a href="ch10-00-generics.html"><strong aria-hidden="true">10.</strong> Generic Types, Traits, and Lifetimes</a></li><li><ol class="section"><li class="expanded "><a href="ch10-01-syntax.html"><strong aria-hidden="true">10.1.</strong> Generic Data Types</a></li><li class="expanded "><a href="ch10-02-traits.html"><strong aria-hidden="true">10.2.</strong> Traits: Defining Shared Behavior</a></li><li class="expanded "><a href="ch10-03-lifetime-syntax.html"><strong aria-hidden="true">10.3.</strong> Validating References with Lifetimes</a></li></ol></li><li class="expanded "><a href="ch11-00-testing.html"><strong aria-hidden="true">11.</strong> Writing Automated Tests</a></li><li><ol class="section"><li class="expanded "><a href="ch11-01-writing-tests.html"><strong aria-hidden="true">11.1.</strong> How to Write Tests</a></li><li class="expanded "><a href="ch11-02-running-tests.html"><strong aria-hidden="true">11.2.</strong> Controlling How Tests Are Run</a></li><li class="expanded "><a href="ch11-03-test-organization.html"><strong aria-hidden="true">11.3.</strong> Test Organization</a></li></ol></li><li class="expanded "><a href="ch12-00-an-io-project.html"><strong aria-hidden="true">12.</strong> An I/O Project: Building a Command Line Program</a></li><li><ol class="section"><li class="expanded "><a href="ch12-01-accepting-command-line-arguments.html"><strong aria-hidden="true">12.1.</strong> Accepting Command Line Arguments</a></li><li class="expanded "><a href="ch12-02-reading-a-file.html"><strong aria-hidden="true">12.2.</strong> Reading a File</a></li><li class="expanded "><a href="ch12-03-improving-error-handling-and-modularity.html"><strong aria-hidden="true">12.3.</strong> Refactoring to Improve Modularity and Error Handling</a></li><li class="expanded "><a href="ch12-04-testing-the-librarys-functionality.html"><strong aria-hidden="true">12.4.</strong> Developing the Library’s Functionality with Test Driven Development</a></li><li class="expanded "><a href="ch12-05-working-with-environment-variables.html"><strong aria-hidden="true">12.5.</strong> Working with Environment Variables</a></li><li class="expanded "><a href="ch12-06-writing-to-stderr-instead-of-stdout.html"><strong aria-hidden="true">12.6.</strong> Writing Error Messages to Standard Error Instead of Standard Output</a></li></ol></li><li class="expanded "><a href="ch13-00-functional-features.html"><strong aria-hidden="true">13.</strong> Functional Language Features: Iterators and Closures</a></li><li><ol class="section"><li class="expanded "><a href="ch13-01-closures.html"><strong aria-hidden="true">13.1.</strong> Closures: Anonymous Functions that Can Capture Their Environment</a></li><li class="expanded "><a href="ch13-02-iterators.html"><strong aria-hidden="true">13.2.</strong> Processing a Series of Items with Iterators</a></li><li class="expanded "><a href="ch13-03-improving-our-io-project.html"><strong aria-hidden="true">13.3.</strong> Improving Our I/O Project</a></li><li class="expanded "><a href="ch13-04-performance.html"><strong aria-hidden="true">13.4.</strong> Comparing Performance: Loops vs. Iterators</a></li></ol></li><li class="expanded "><a href="ch14-00-more-about-cargo.html"><strong aria-hidden="true">14.</strong> More about Cargo and Crates.io</a></li><li><ol class="section"><li class="expanded "><a href="ch14-01-release-profiles.html"><strong aria-hidden="true">14.1.</strong> Customizing Builds with Release Profiles</a></li><li class="expanded "><a href="ch14-02-publishing-to-crates-io.html"><strong aria-hidden="true">14.2.</strong> Publishing a Crate to Crates.io</a></li><li class="expanded "><a href="ch14-03-cargo-workspaces.html"><strong aria-hidden="true">14.3.</strong> Cargo Workspaces</a></li><li class="expanded "><a href="ch14-04-installing-binaries.html"><strong aria-hidden="true">14.4.</strong> Installing Binaries from Crates.io with cargo install</a></li><li class="expanded "><a href="ch14-05-extending-cargo.html"><strong aria-hidden="true">14.5.</strong> Extending Cargo with Custom Commands</a></li></ol></li><li class="expanded "><a href="ch15-00-smart-pointers.html"><strong aria-hidden="true">15.</strong> Smart Pointers</a></li><li><ol class="section"><li class="expanded "><a href="ch15-01-box.html"><strong aria-hidden="true">15.1.</strong> Using Box<T> to Point to Data on the Heap</a></li><li class="expanded "><a href="ch15-02-deref.html"><strong aria-hidden="true">15.2.</strong> Treating Smart Pointers Like Regular References with the Deref Trait</a></li><li class="expanded "><a href="ch15-03-drop.html"><strong aria-hidden="true">15.3.</strong> Running Code on Cleanup with the Drop Trait</a></li><li class="expanded "><a href="ch15-04-rc.html"><strong aria-hidden="true">15.4.</strong> Rc<T>, the Reference Counted Smart Pointer</a></li><li class="expanded "><a href="ch15-05-interior-mutability.html"><strong aria-hidden="true">15.5.</strong> RefCell<T> and the Interior Mutability Pattern</a></li><li class="expanded "><a href="ch15-06-reference-cycles.html"><strong aria-hidden="true">15.6.</strong> Reference Cycles Can Leak Memory</a></li></ol></li><li class="expanded "><a href="ch16-00-concurrency.html"><strong aria-hidden="true">16.</strong> Fearless Concurrency</a></li><li><ol class="section"><li class="expanded "><a href="ch16-01-threads.html"><strong aria-hidden="true">16.1.</strong> Using Threads to Run Code Simultaneously</a></li><li class="expanded "><a href="ch16-02-message-passing.html"><strong aria-hidden="true">16.2.</strong> Using Message Passing to Transfer Data Between Threads</a></li><li class="expanded "><a href="ch16-03-shared-state.html"><strong aria-hidden="true">16.3.</strong> Shared-State Concurrency</a></li><li class="expanded "><a href="ch16-04-extensible-concurrency-sync-and-send.html"><strong aria-hidden="true">16.4.</strong> Extensible Concurrency with the Sync and Send Traits</a></li></ol></li><li class="expanded "><a href="ch17-00-oop.html"><strong aria-hidden="true">17.</strong> Object Oriented Programming Features of Rust</a></li><li><ol class="section"><li class="expanded "><a href="ch17-01-what-is-oo.html"><strong aria-hidden="true">17.1.</strong> Characteristics of Object-Oriented Languages</a></li><li class="expanded "><a href="ch17-02-trait-objects.html"><strong aria-hidden="true">17.2.</strong> Using Trait Objects That Allow for Values of Different Types</a></li><li class="expanded "><a href="ch17-03-oo-design-patterns.html"><strong aria-hidden="true">17.3.</strong> Implementing an Object-Oriented Design Pattern</a></li></ol></li><li class="expanded "><a href="ch18-00-patterns.html"><strong aria-hidden="true">18.</strong> Patterns and Matching</a></li><li><ol class="section"><li class="expanded "><a href="ch18-01-all-the-places-for-patterns.html"><strong aria-hidden="true">18.1.</strong> All the Places Patterns Can Be Used</a></li><li class="expanded "><a href="ch18-02-refutability.html"><strong aria-hidden="true">18.2.</strong> Refutability: Whether a Pattern Might Fail to Match</a></li><li class="expanded "><a href="ch18-03-pattern-syntax.html"><strong aria-hidden="true">18.3.</strong> Pattern Syntax</a></li></ol></li><li class="expanded "><a href="ch19-00-advanced-features.html"><strong aria-hidden="true">19.</strong> Advanced Features</a></li><li><ol class="section"><li class="expanded "><a href="ch19-01-unsafe-rust.html"><strong aria-hidden="true">19.1.</strong> Unsafe Rust</a></li><li class="expanded "><a href="ch19-03-advanced-traits.html"><strong aria-hidden="true">19.2.</strong> Advanced Traits</a></li><li class="expanded "><a href="ch19-04-advanced-types.html"><strong aria-hidden="true">19.3.</strong> Advanced Types</a></li><li class="expanded "><a href="ch19-05-advanced-functions-and-closures.html"><strong aria-hidden="true">19.4.</strong> Advanced Functions and Closures</a></li><li class="expanded "><a href="ch19-06-macros.html"><strong aria-hidden="true">19.5.</strong> Macros</a></li></ol></li><li class="expanded "><a href="ch20-00-final-project-a-web-server.html"><strong aria-hidden="true">20.</strong> Final Project: Building a Multithreaded Web Server</a></li><li><ol class="section"><li class="expanded "><a href="ch20-01-single-threaded.html"><strong aria-hidden="true">20.1.</strong> Building a Single-Threaded Web Server</a></li><li class="expanded "><a href="ch20-02-multithreaded.html"><strong aria-hidden="true">20.2.</strong> Turning Our Single-Threaded Server into a Multithreaded Server</a></li><li class="expanded "><a href="ch20-03-graceful-shutdown-and-cleanup.html"><strong aria-hidden="true">20.3.</strong> Graceful Shutdown and Cleanup</a></li></ol></li><li class="expanded "><a href="appendix-00.html"><strong aria-hidden="true">21.</strong> Appendix</a></li><li><ol class="section"><li class="expanded "><a href="appendix-01-keywords.html"><strong aria-hidden="true">21.1.</strong> A - Keywords</a></li><li class="expanded "><a href="appendix-02-operators.html"><strong aria-hidden="true">21.2.</strong> B - Operators and Symbols</a></li><li class="expanded "><a href="appendix-03-derivable-traits.html"><strong aria-hidden="true">21.3.</strong> C - Derivable Traits</a></li><li class="expanded "><a href="appendix-04-useful-development-tools.html"><strong aria-hidden="true">21.4.</strong> D - Useful Development Tools</a></li><li class="expanded "><a href="appendix-05-editions.html"><strong aria-hidden="true">21.5.</strong> E - Editions</a></li><li class="expanded "><a href="appendix-06-translation.html"><strong aria-hidden="true">21.6.</strong> F - Translations of the Book</a></li><li class="expanded "><a href="appendix-07-nightly-rust.html" class="active"><strong aria-hidden="true">21.7.</strong> G - How Rust is Made and “Nightly Rust”</a></li></ol></li></ol>
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<h1 class="menu-title">The Rust Programming Language</h1>
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<h2><a class="header" href="#appendix-g---how-rust-is-made-and-nightly-rust" id="appendix-g---how-rust-is-made-and-nightly-rust">Appendix G - How Rust is Made and “Nightly Rust”</a></h2>
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<p>This appendix is about how Rust is made and how that affects you as a Rust
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developer.</p>
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<h3><a class="header" href="#stability-without-stagnation" id="stability-without-stagnation">Stability Without Stagnation</a></h3>
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<p>As a language, Rust cares a <em>lot</em> about the stability of your code. We want
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Rust to be a rock-solid foundation you can build on, and if things were
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constantly changing, that would be impossible. At the same time, if we can’t
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experiment with new features, we may not find out important flaws until after
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their release, when we can no longer change things.</p>
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<p>Our solution to this problem is what we call “stability without stagnation”,
|
||
and our guiding principle is this: you should never have to fear upgrading to a
|
||
new version of stable Rust. Each upgrade should be painless, but should also
|
||
bring you new features, fewer bugs, and faster compile times.</p>
|
||
<h3><a class="header" href="#choo-choo-release-channels-and-riding-the-trains" id="choo-choo-release-channels-and-riding-the-trains">Choo, Choo! Release Channels and Riding the Trains</a></h3>
|
||
<p>Rust development operates on a <em>train schedule</em>. That is, all development is
|
||
done on the <code>master</code> branch of the Rust repository. Releases follow a software
|
||
release train model, which has been used by Cisco IOS and other software
|
||
projects. There are three <em>release channels</em> for Rust:</p>
|
||
<ul>
|
||
<li>Nightly</li>
|
||
<li>Beta</li>
|
||
<li>Stable</li>
|
||
</ul>
|
||
<p>Most Rust developers primarily use the stable channel, but those who want to
|
||
try out experimental new features may use nightly or beta.</p>
|
||
<p>Here’s an example of how the development and release process works: let’s
|
||
assume that the Rust team is working on the release of Rust 1.5. That release
|
||
happened in December of 2015, but it will provide us with realistic version
|
||
numbers. A new feature is added to Rust: a new commit lands on the <code>master</code>
|
||
branch. Each night, a new nightly version of Rust is produced. Every day is a
|
||
release day, and these releases are created by our release infrastructure
|
||
automatically. So as time passes, our releases look like this, once a night:</p>
|
||
<pre><code class="language-text">nightly: * - - * - - *
|
||
</code></pre>
|
||
<p>Every six weeks, it’s time to prepare a new release! The <code>beta</code> branch of the
|
||
Rust repository branches off from the <code>master</code> branch used by nightly. Now,
|
||
there are two releases:</p>
|
||
<pre><code class="language-text">nightly: * - - * - - *
|
||
|
|
||
beta: *
|
||
</code></pre>
|
||
<p>Most Rust users do not use beta releases actively, but test against beta in
|
||
their CI system to help Rust discover possible regressions. In the meantime,
|
||
there’s still a nightly release every night:</p>
|
||
<pre><code class="language-text">nightly: * - - * - - * - - * - - *
|
||
|
|
||
beta: *
|
||
</code></pre>
|
||
<p>Let’s say a regression is found. Good thing we had some time to test the beta
|
||
release before the regression snuck into a stable release! The fix is applied
|
||
to <code>master</code>, so that nightly is fixed, and then the fix is backported to the
|
||
<code>beta</code> branch, and a new release of beta is produced:</p>
|
||
<pre><code class="language-text">nightly: * - - * - - * - - * - - * - - *
|
||
|
|
||
beta: * - - - - - - - - *
|
||
</code></pre>
|
||
<p>Six weeks after the first beta was created, it’s time for a stable release! The
|
||
<code>stable</code> branch is produced from the <code>beta</code> branch:</p>
|
||
<pre><code class="language-text">nightly: * - - * - - * - - * - - * - - * - * - *
|
||
|
|
||
beta: * - - - - - - - - *
|
||
|
|
||
stable: *
|
||
</code></pre>
|
||
<p>Hooray! Rust 1.5 is done! However, we’ve forgotten one thing: because the six
|
||
weeks have gone by, we also need a new beta of the <em>next</em> version of Rust, 1.6.
|
||
So after <code>stable</code> branches off of <code>beta</code>, the next version of <code>beta</code> branches
|
||
off of <code>nightly</code> again:</p>
|
||
<pre><code class="language-text">nightly: * - - * - - * - - * - - * - - * - * - *
|
||
| |
|
||
beta: * - - - - - - - - * *
|
||
|
|
||
stable: *
|
||
</code></pre>
|
||
<p>This is called the “train model” because every six weeks, a release “leaves the
|
||
station”, but still has to take a journey through the beta channel before it
|
||
arrives as a stable release.</p>
|
||
<p>Rust releases every six weeks, like clockwork. If you know the date of one Rust
|
||
release, you can know the date of the next one: it’s six weeks later. A nice
|
||
aspect of having releases scheduled every six weeks is that the next train is
|
||
coming soon. If a feature happens to miss a particular release, there’s no need
|
||
to worry: another one is happening in a short time! This helps reduce pressure
|
||
to sneak possibly unpolished features in close to the release deadline.</p>
|
||
<p>Thanks to this process, you can always check out the next build of Rust and
|
||
verify for yourself that it’s easy to upgrade to: if a beta release doesn’t
|
||
work as expected, you can report it to the team and get it fixed before the
|
||
next stable release happens! Breakage in a beta release is relatively rare, but
|
||
<code>rustc</code> is still a piece of software, and bugs do exist.</p>
|
||
<h3><a class="header" href="#unstable-features" id="unstable-features">Unstable Features</a></h3>
|
||
<p>There’s one more catch with this release model: unstable features. Rust uses a
|
||
technique called “feature flags” to determine what features are enabled in a
|
||
given release. If a new feature is under active development, it lands on
|
||
<code>master</code>, and therefore, in nightly, but behind a <em>feature flag</em>. If you, as a
|
||
user, wish to try out the work-in-progress feature, you can, but you must be
|
||
using a nightly release of Rust and annotate your source code with the
|
||
appropriate flag to opt in.</p>
|
||
<p>If you’re using a beta or stable release of Rust, you can’t use any feature
|
||
flags. This is the key that allows us to get practical use with new features
|
||
before we declare them stable forever. Those who wish to opt into the bleeding
|
||
edge can do so, and those who want a rock-solid experience can stick with
|
||
stable and know that their code won’t break. Stability without stagnation.</p>
|
||
<p>This book only contains information about stable features, as in-progress
|
||
features are still changing, and surely they’ll be different between when this
|
||
book was written and when they get enabled in stable builds. You can find
|
||
documentation for nightly-only features online.</p>
|
||
<h3><a class="header" href="#rustup-and-the-role-of-rust-nightly" id="rustup-and-the-role-of-rust-nightly">Rustup and the Role of Rust Nightly</a></h3>
|
||
<p>Rustup makes it easy to change between different release channels of Rust, on a
|
||
global or per-project basis. By default, you’ll have stable Rust installed. To
|
||
install nightly, for example:</p>
|
||
<pre><code class="language-text">$ rustup install nightly
|
||
</code></pre>
|
||
<p>You can see all of the <em>toolchains</em> (releases of Rust and associated
|
||
components) you have installed with <code>rustup</code> as well. Here’s an example on one
|
||
of your authors’ Windows computer:</p>
|
||
<pre><code class="language-powershell">> rustup toolchain list
|
||
stable-x86_64-pc-windows-msvc (default)
|
||
beta-x86_64-pc-windows-msvc
|
||
nightly-x86_64-pc-windows-msvc
|
||
</code></pre>
|
||
<p>As you can see, the stable toolchain is the default. Most Rust users use stable
|
||
most of the time. You might want to use stable most of the time, but use
|
||
nightly on a specific project, because you care about a cutting-edge feature.
|
||
To do so, you can use <code>rustup override</code> in that project’s directory to set the
|
||
nightly toolchain as the one <code>rustup</code> should use when you’re in that directory:</p>
|
||
<pre><code class="language-text">$ cd ~/projects/needs-nightly
|
||
$ rustup override set nightly
|
||
</code></pre>
|
||
<p>Now, every time you call <code>rustc</code> or <code>cargo</code> inside of
|
||
<em>~/projects/needs-nightly</em>, <code>rustup</code> will make sure that you are using nightly
|
||
Rust, rather than your default of stable Rust. This comes in handy when you
|
||
have a lot of Rust projects!</p>
|
||
<h3><a class="header" href="#the-rfc-process-and-teams" id="the-rfc-process-and-teams">The RFC Process and Teams</a></h3>
|
||
<p>So how do you learn about these new features? Rust’s development model follows
|
||
a <em>Request For Comments (RFC) process</em>. If you’d like an improvement in Rust,
|
||
you can write up a proposal, called an RFC.</p>
|
||
<p>Anyone can write RFCs to improve Rust, and the proposals are reviewed and
|
||
discussed by the Rust team, which is comprised of many topic subteams. There’s
|
||
a full list of the teams <a href="https://www.rust-lang.org/governance">on Rust’s
|
||
website</a>, which includes teams for
|
||
each area of the project: language design, compiler implementation,
|
||
infrastructure, documentation, and more. The appropriate team reads the
|
||
proposal and the comments, writes some comments of their own, and eventually,
|
||
there’s consensus to accept or reject the feature.</p>
|
||
<p>If the feature is accepted, an issue is opened on the Rust repository, and
|
||
someone can implement it. The person who implements it very well may not be the
|
||
person who proposed the feature in the first place! When the implementation is
|
||
ready, it lands on the <code>master</code> branch behind a feature gate, as we discussed
|
||
in the <a href="#unstable-features">“Unstable Features”</a><!-- ignore --> section.</p>
|
||
<p>After some time, once Rust developers who use nightly releases have been able
|
||
to try out the new feature, team members will discuss the feature, how it’s
|
||
worked out on nightly, and decide if it should make it into stable Rust or not.
|
||
If the decision is to move forward, the feature gate is removed, and the
|
||
feature is now considered stable! It rides the trains into a new stable release
|
||
of Rust.</p>
|
||
|
||
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|
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