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| <ol class="chapter"><li class="chapter-item affix "><a href="about-this-guide.html">About this guide</a></li><li class="chapter-item affix "><a href="getting-started.html">Getting Started</a></li><li class="spacer"></li><li class="chapter-item affix "><li class="part-title">Building and debugging rustc</li><li class="chapter-item "><a href="building/how-to-build-and-run.html"><strong aria-hidden="true">1.</strong> How to Build and Run the Compiler</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="building/prerequisites.html"><strong aria-hidden="true">1.1.</strong> Prerequisites</a></li><li class="chapter-item "><a href="building/suggested.html"><strong aria-hidden="true">1.2.</strong> Suggested Workflows</a></li><li class="chapter-item "><a href="building/build-install-distribution-artifacts.html"><strong aria-hidden="true">1.3.</strong> Distribution artifacts</a></li><li class="chapter-item "><a href="building/compiler-documenting.html"><strong aria-hidden="true">1.4.</strong> Documenting Compiler</a></li><li class="chapter-item "><a href="rustdoc.html"><strong aria-hidden="true">1.5.</strong> Rustdoc overview</a></li><li class="chapter-item "><a href="building/new-target.html"><strong aria-hidden="true">1.6.</strong> Adding a new target</a></li></ol></li><li class="chapter-item "><a href="tests/intro.html"><strong aria-hidden="true">2.</strong> The compiler testing framework</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="tests/running.html"><strong aria-hidden="true">2.1.</strong> Running tests</a></li><li class="chapter-item "><a href="tests/adding.html"><strong aria-hidden="true">2.2.</strong> Adding new tests</a></li><li class="chapter-item "><a href="compiletest.html"><strong aria-hidden="true">2.3.</strong> Using compiletest commands to control test execution</a></li></ol></li><li class="chapter-item "><a href="compiler-debugging.html"><strong aria-hidden="true">3.</strong> Debugging the Compiler</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="tracing.html"><strong aria-hidden="true">3.1.</strong> Using the tracing/logging instrumentation</a></li></ol></li><li class="chapter-item "><a href="profiling.html"><strong aria-hidden="true">4.</strong> Profiling the compiler</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="profiling/with_perf.html"><strong aria-hidden="true">4.1.</strong> with the linux perf tool</a></li><li class="chapter-item "><a href="profiling/wpa_profiling.html"><strong aria-hidden="true">4.2.</strong> with Windows Performance Analyzer</a></li></ol></li><li class="chapter-item "><a href="crates-io.html"><strong aria-hidden="true">5.</strong> crates.io Dependencies</a></li><li class="chapter-item affix "><li class="part-title">Contributing to Rust</li><li class="chapter-item "><a href="contributing.html"><strong aria-hidden="true">6.</strong> Introduction</a></li><li class="chapter-item "><a href="compiler-team.html"><strong aria-hidden="true">7.</strong> About the compiler team</a></li><li class="chapter-item "><a href="git.html"><strong aria-hidden="true">8.</strong> Using Git</a></li><li class="chapter-item "><a href="rustbot.html"><strong aria-hidden="true">9.</strong> Mastering @rustbot</a></li><li class="chapter-item "><a href="walkthrough.html"><strong aria-hidden="true">10.</strong> Walkthrough: a typical contribution</a></li><li class="chapter-item "><a href="bug-fix-procedure.html"><strong aria-hidden="true">11.</strong> Bug Fix Procedure</a></li><li class="chapter-item "><a href="implementing_new_features.html"><strong aria-hidden="true">12.</strong> Implementing new features</a></li><li class="chapter-item "><a href="stability.html"><strong aria-hidden="true">13.</strong> Stability attributes</a></li><li class="chapter-item expanded "><a href="stabilization_guide.html" class="active"><strong aria-hidden="true">14.</strong> Stabilizing Features</a></li><li class="chapter-item "><a href="feature-gates.html"><strong aria-hidden="true">15.</strong> Feature Gates</a></li><li class="chapter-item "><a href="conventions.html"><strong aria-hidden="true">16.</strong> Coding conventions</a></li><li class="chapter-item "><a href="notification-groups/about.html"><strong aria-hidden="true">17.</strong> Notification groups</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="notification-groups/arm.html"><strong aria-hidden="true">17.1.</strong> ARM</a></li><li class="chapter-item "><a href="notification-groups/cleanup-crew.html"><strong aria-hidden="true">17.2.</strong> Cleanup Crew</a></li><li class="chapter-item "><a href="notification-groups/llvm.html"><strong aria-hidden="true">17.3.</strong> LLVM</a></li><li class="chapter-item "><a href="notification-groups/risc-v.html"><strong aria-hidden="true">17.4.</strong> RISC-V</a></li><li class="chapter-item "><a href="notification-groups/windows.html"><strong aria-hidden="true">17.5.</strong> Windows</a></li></ol></li><li class="chapter-item "><a href="licenses.html"><strong aria-hidden="true">18.</strong> Licenses</a></li><li class="chapter-item affix "><li class="part-title">High-level Compiler Architecture</li><li class="chapter-item "><a href="part-2-intro.html"><strong aria-hidden="true">19.</strong> Prologue</a></li><li class="chapter-item "><a href="overview.html"><strong aria-hidden="true">20.</strong> Overview of the Compiler</a></li><li class="chapter-item "><a href="compiler-src.html"><strong aria-hidden="true">21.</strong> The compiler source code</a></li><li class="chapter-item "><a href="building/bootstrapping.html"><strong aria-hidden="true">22.</strong> Bootstrapping</a></li><li class="chapter-item "><a href="query.html"><strong aria-hidden="true">23.</strong> Queries: demand-driven compilation</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="queries/query-evaluation-model-in-detail.html"><strong aria-hidden="true">23.1.</strong> The Query Evaluation Model in Detail</a></li><li class="chapter-item "><a href="queries/incremental-compilation.html"><strong aria-hidden="true">23.2.</strong> Incremental compilation</a></li><li class="chapter-item "><a href="queries/incremental-compilation-in-detail.html"><strong aria-hidden="true">23.3.</strong> Incremental compilation In Detail</a></li><li class="chapter-item "><a href="incrcomp-debugging.html"><strong aria-hidden="true">23.4.</strong> Debugging and Testing</a></li><li class="chapter-item "><a href="salsa.html"><strong aria-hidden="true">23.5.</strong> Salsa</a></li></ol></li><li class="chapter-item "><a href="memory.html"><strong aria-hidden="true">24.</strong> Memory Management in Rustc</a></li><li class="chapter-item "><a href="serialization.html"><strong aria-hidden="true">25.</strong> Serialization in Rustc</a></li><li class="chapter-item "><a href="parallel-rustc.html"><strong aria-hidden="true">26.</strong> Parallel Compilation</a></li><li class="chapter-item "><a href="rustdoc-internals.html"><strong aria-hidden="true">27.</strong> Rustdoc internals</a></li><li class="chapter-item affix "><li class="part-title">Source Code Representation</li><li class="chapter-item "><a href="part-3-intro.html"><strong aria-hidden="true">28.</strong> Prologue</a></li><li class="chapter-item "><a href="cli.html"><strong aria-hidden="true">29.</strong> Command-line arguments</a></li><li class="chapter-item "><a href="rustc-driver.html"><strong aria-hidden="true">30.</strong> The Rustc Driver and Interface</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="rustc-driver-interacting-with-the-ast.html"><strong aria-hidden="true">30.1.</strong> Ex: Type checking through rustc_interface</a></li><li class="chapter-item "><a href="rustc-driver-getting-diagnostics.html"><strong aria-hidden="true">30.2.</strong> Ex: Getting diagnostics through rustc_interface</a></li></ol></li><li class="chapter-item "><a href="syntax-intro.html"><strong aria-hidden="true">31.</strong> Syntax and the AST</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="the-parser.html"><strong aria-hidden="true">31.1.</strong> Lexing and Parsing</a></li><li class="chapter-item "><a href="macro-expansion.html"><strong aria-hidden="true">31.2.</strong> Macro expansion</a></li><li class="chapter-item "><a href="name-resolution.html"><strong aria-hidden="true">31.3.</strong> Name resolution</a></li><li class="chapter-item "><a href="test-implementation.html"><strong aria-hidden="true">31.4.</strong> #[test] Implementation</a></li><li class="chapter-item "><a href="panic-implementation.html"><strong aria-hidden="true">31.5.</strong> Panic Implementation</a></li><li class="chapter-item "><a href="ast-validation.html"><strong aria-hidden="true">31.6.</strong> AST Validation</a></li><li class="chapter-item "><a href="feature-gate-ck.html"><strong aria-hidden="true">31.7.</strong> Feature Gate Checking</a></li><li class="chapter-item "><a href="lang-items.html"><strong aria-hidden="true">31.8.</strong> Lang Items</a></li></ol></li><li class="chapter-item "><a href="hir.html"><strong aria-hidden="true">32.</strong> The HIR (High-level IR)</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="lowering.html"><strong aria-hidden="true">32.1.</strong> Lowering AST to HIR</a></li><li class="chapter-item "><a href="hir-debugging.html"><strong aria-hidden="true">32.2.</strong> Debugging</a></li></ol></li><li class="chapter-item "><a href="thir.html"><strong aria-hidden="true">33.</strong> The THIR (Typed High-level IR)</a></li><li class="chapter-item "><a href="mir/index.html"><strong aria-hidden="true">34.</strong> The MIR (Mid-level IR)</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="mir/construction.html"><strong aria-hidden="true">34.1.</strong> MIR construction</a></li><li class="chapter-item "><a href="mir/visitor.html"><strong aria-hidden="true">34.2.</strong> MIR visitor and traversal</a></li><li class="chapter-item "><a href="mir/passes.html"><strong aria-hidden="true">34.3.</strong> MIR passes: getting the MIR for a function</a></li></ol></li><li class="chapter-item "><a href="identifiers.html"><strong aria-hidden="true">35.</strong> Identifiers in the Compiler</a></li><li class="chapter-item "><a href="closure.html"><strong aria-hidden="true">36.</strong> Closure expansion</a></li><li class="chapter-item affix "><li class="part-title">Analysis</li><li class="chapter-item "><a href="part-4-intro.html"><strong aria-hidden="true">37.</strong> Prologue</a></li><li class="chapter-item "><a href="ty.html"><strong aria-hidden="true">38.</strong> The ty module: representing types</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="generics.html"><strong aria-hidden="true">38.1.</strong> Generics and substitutions</a></li><li class="chapter-item "><a href="ty-fold.html"><strong aria-hidden="true">38.2.</strong> TypeFolder and TypeFoldable</a></li><li class="chapter-item "><a href="generic_arguments.html"><strong aria-hidden="true">38.3.</strong> Generic arguments</a></li><li class="chapter-item "><a href="constants.html"><strong aria-hidden="true">38.4.</strong> Constants in the type system</a></li></ol></li><li class="chapter-item "><a href="type-inference.html"><strong aria-hidden="true">39.</strong> Type inference</a></li><li class="chapter-item "><a href="traits/resolution.html"><strong aria-hidden="true">40.</strong> Trait solving</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="early-late-bound.html"><strong aria-hidden="true">40.1.</strong> Early and Late Bound Parameters</a></li><li class="chapter-item "><a href="traits/hrtb.html"><strong aria-hidden="true">40.2.</strong> Higher-ranked trait bounds</a></li><li class="chapter-item "><a href="traits/caching.html"><strong aria-hidden="true">40.3.</strong> Caching subtleties</a></li><li class="chapter-item "><a href="traits/specialization.html"><strong aria-hidden="true">40.4.</strong> Specialization</a></li><li class="chapter-item "><a href="traits/chalk.html"><strong aria-hidden="true">40.5.</strong> Chalk-based trait solving</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="traits/lowering-to-logic.html"><strong aria-hidden="true">40.5.1.</strong> Lowering to logic</a></li><li class="chapter-item "><a href="traits/goals-and-clauses.html"><strong aria-hidden="true">40.5.2.</strong> Goals and clauses</a></li><li class="chapter-item "><a href="traits/canonical-queries.html"><strong aria-hidden="true">40.5.3.</strong> Canonical queries</a></li></ol></li></ol></li><li class="chapter-item "><a href="type-checking.html"><strong aria-hidden="true">41.</strong> Type checking</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="method-lookup.html"><strong aria-hidden="true">41.1.</strong> Method Lookup</a></li><li class="chapter-item "><a href="variance.html"><strong aria-hidden="true">41.2.</strong> Variance</a></li><li class="chapter-item "><a href="opaque-types-type-alias-impl-trait.html"><strong aria-hidden="true">41.3.</strong> Opaque Types</a></li></ol></li><li class="chapter-item "><a href="pat-exhaustive-checking.html"><strong aria-hidden="true">42.</strong> Pattern and Exhaustiveness Checking</a></li><li class="chapter-item "><a href="mir/dataflow.html"><strong aria-hidden="true">43.</strong> MIR dataflow</a></li><li class="chapter-item "><a href="borrow_check.html"><strong aria-hidden="true">44.</strong> The borrow checker</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="borrow_check/moves_and_initialization.html"><strong aria-hidden="true">44.1.</strong> Tracking moves and initialization</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="borrow_check/moves_and_initialization/move_paths.html"><strong aria-hidden="true">44.1.1.</strong> Move paths</a></li></ol></li><li class="chapter-item "><a href="borrow_check/type_check.html"><strong aria-hidden="true">44.2.</strong> MIR type checker</a></li><li class="chapter-item "><a href="borrow_check/region_inference.html"><strong aria-hidden="true">44.3.</strong> Region inference</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="borrow_check/region_inference/constraint_propagation.html"><strong aria-hidden="true">44.3.1.</strong> Constraint propagation</a></li><li class="chapter-item "><a href="borrow_check/region_inference/lifetime_parameters.html"><strong aria-hidden="true">44.3.2.</strong> Lifetime parameters</a></li><li class="chapter-item "><a href="borrow_check/region_inference/member_constraints.html"><strong aria-hidden="true">44.3.3.</strong> Member constraints</a></li><li class="chapter-item "><a href="borrow_check/region_inference/placeholders_and_universes.html"><strong aria-hidden="true">44.3.4.</strong> Placeholders and universes</a></li><li class="chapter-item "><a href="borrow_check/region_inference/closure_constraints.html"><strong aria-hidden="true">44.3.5.</strong> Closure constraints</a></li><li class="chapter-item "><a href="borrow_check/region_inference/error_reporting.html"><strong aria-hidden="true">44.3.6.</strong> Error reporting</a></li></ol></li><li class="chapter-item "><a href="borrow_check/two_phase_borrows.html"><strong aria-hidden="true">44.4.</strong> Two-phase-borrows</a></li></ol></li><li class="chapter-item "><a href="param_env.html"><strong aria-hidden="true">45.</strong> Parameter Environments</a></li><li class="chapter-item "><a href="diagnostics.html"><strong aria-hidden="true">46.</strong> Errors and Lints</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="diagnostics/sessiondiagnostic.html"><strong aria-hidden="true">46.1.</strong> Creating Errors With SessionDiagnostic</a></li><li class="chapter-item "><a href="diagnostics/lintstore.html"><strong aria-hidden="true">46.2.</strong> LintStore</a></li><li class="chapter-item "><a href="diagnostics/diagnostic-codes.html"><strong aria-hidden="true">46.3.</strong> Diagnostic Codes</a></li><li class="chapter-item "><a href="diagnostics/diagnostic-items.html"><strong aria-hidden="true">46.4.</strong> Diagnostic Items</a></li></ol></li><li class="chapter-item "><li class="part-title">MIR to Binaries</li><li class="chapter-item "><a href="part-5-intro.html"><strong aria-hidden="true">47.</strong> Prologue</a></li><li class="chapter-item "><a href="mir/optimizations.html"><strong aria-hidden="true">48.</strong> MIR optimizations</a></li><li class="chapter-item "><a href="mir/debugging.html"><strong aria-hidden="true">49.</strong> Debugging</a></li><li class="chapter-item "><a href="const-eval.html"><strong aria-hidden="true">50.</strong> Constant evaluation</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="miri.html"><strong aria-hidden="true">50.1.</strong> miri const evaluator</a></li></ol></li><li class="chapter-item "><a href="backend/monomorph.html"><strong aria-hidden="true">51.</strong> Monomorphization</a></li><li class="chapter-item "><a href="backend/lowering-mir.html"><strong aria-hidden="true">52.</strong> Lowering MIR</a></li><li class="chapter-item "><a href="backend/codegen.html"><strong aria-hidden="true">53.</strong> Code Generation</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="backend/updating-llvm.html"><strong aria-hidden="true">53.1.</strong> Updating LLVM</a></li><li class="chapter-item "><a href="backend/debugging.html"><strong aria-hidden="true">53.2.</strong> Debugging LLVM</a></li><li class="chapter-item "><a href="backend/backend-agnostic.html"><strong aria-hidden="true">53.3.</strong> Backend Agnostic Codegen</a></li><li class="chapter-item "><a href="backend/implicit-caller-location.html"><strong aria-hidden="true">53.4.</strong> Implicit Caller Location</a></li></ol></li><li class="chapter-item "><a href="backend/libs-and-metadata.html"><strong aria-hidden="true">54.</strong> Libraries and Metadata</a></li><li class="chapter-item "><a href="profile-guided-optimization.html"><strong aria-hidden="true">55.</strong> Profile-guided Optimization</a></li><li class="chapter-item "><a href="llvm-coverage-instrumentation.html"><strong aria-hidden="true">56.</strong> LLVM Source-Based Code Coverage</a></li><li class="chapter-item "><a href="sanitizers.html"><strong aria-hidden="true">57.</strong> Sanitizers Support</a></li><li class="chapter-item "><a href="debugging-support-in-rustc.html"><strong aria-hidden="true">58.</strong> Debugging Support in the Rust Compiler</a></li><li class="spacer"></li><li class="chapter-item affix "><a href="appendix/background.html">Appendix A: Background topics</a></li><li class="chapter-item affix "><a href="appendix/glossary.html">Appendix B: Glossary</a></li><li class="chapter-item affix "><a href="appendix/code-index.html">Appendix C: Code Index</a></li><li class="chapter-item affix "><a href="appendix/compiler-lecture.html">Appendix D: Compiler Lecture Series</a></li><li class="chapter-item affix "><a href="appendix/bibliography.html">Appendix E: Bibliography</a></li><li class="chapter-item affix "><a href="appendix/humorust.html">Appendix Z: HumorRust</a></li><li class="spacer"></li></ol> |
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| <h1 id="request-for-stabilization"><a class="header" href="#request-for-stabilization">Request for stabilization</a></h1> |
| <p><strong>NOTE</strong>: this page is about stabilizing language features. |
| For stabilizing <em>library</em> features, see <a href="./stability.html#stabilizing-a-library-feature">Stabilizing a library feature</a>.</p> |
| <p>Once an unstable feature has been well-tested with no outstanding |
| concern, anyone may push for its stabilization. It involves the |
| following steps:</p> |
| <ul> |
| <li><a href="#documentation-prs">Documentation PRs</a></li> |
| <li><a href="#write-a-stabilization-report">Write a stabilization report</a></li> |
| <li><a href="#fcp">FCP</a></li> |
| <li><a href="#stabilization-pr">Stabilization PR</a> |
| <ul> |
| <li><a href="#updating-the-feature-gate-listing">Updating the feature-gate listing</a></li> |
| <li><a href="#removing-existing-uses-of-the-feature-gate">Removing existing uses of the feature-gate</a></li> |
| <li><a href="#do-not-require-the-feature-gate-to-use-the-feature">Do not require the feature-gate to use the feature</a></li> |
| </ul> |
| </li> |
| </ul> |
| <h2 id="documentation-prs"><a class="header" href="#documentation-prs">Documentation PRs</a></h2> |
| <p><a name="updating-documentation"></a></p> |
| <p>If any documentation for this feature exists, it should be |
| in the <a href="https://doc.rust-lang.org/unstable-book/index.html"><code>Unstable Book</code></a>, located at <a href="https://github.com/rust-lang/rust/tree/master/src/doc/unstable-book"><code>src/doc/unstable-book</code></a>. |
| If it exists, the page for the feature gate should be removed.</p> |
| <p>If there was documentation there, integrating it into the |
| existing documentation is needed.</p> |
| <p>If there wasn't documentation there, it needs to be added.</p> |
| <p>Places that may need updated documentation:</p> |
| <ul> |
| <li><a href="https://github.com/rust-lang/reference">The Reference</a>: This must be updated, in full detail.</li> |
| <li><a href="https://github.com/rust-lang/book">The Book</a>: This may or may not need updating, depends. |
| If you're not sure, please open an issue on this repository |
| and it can be discussed.</li> |
| <li>standard library documentation: As needed. Language features |
| often don't need this, but if it's a feature that changes |
| how good examples are written, such as when <code>?</code> was added |
| to the language, updating examples is important.</li> |
| <li><a href="https://github.com/rust-lang/rust-by-example">Rust by Example</a>: As needed.</li> |
| </ul> |
| <p>Prepare PRs to update documentation involving this new feature |
| for repositories mentioned above. Maintainers of these repositories |
| will keep these PRs open until the whole stabilization process |
| has completed. Meanwhile, we can proceed to the next step.</p> |
| <h2 id="write-a-stabilization-report"><a class="header" href="#write-a-stabilization-report">Write a stabilization report</a></h2> |
| <p>Find the tracking issue of the feature, and create a short |
| stabilization report. Essentially this would be a brief summary |
| of the feature plus some links to test cases showing it works |
| as expected, along with a list of edge cases that came up |
| and were considered. This is a minimal "due diligence" that |
| we do before stabilizing.</p> |
| <p>The report should contain:</p> |
| <ul> |
| <li>A summary, showing examples (e.g. code snippets) what is |
| enabled by this feature.</li> |
| <li>Links to test cases in our test suite regarding this feature |
| and describe the feature's behavior on encountering edge cases.</li> |
| <li>Links to the documentations (the PRs we have made in the |
| previous steps).</li> |
| <li>Any other relevant information.</li> |
| <li>The resolutions of any unresolved questions if the stabilization |
| is for an RFC.</li> |
| </ul> |
| <p>Examples of stabilization reports can be found in |
| <a href="https://github.com/rust-lang/rust/issues/44494#issuecomment-360191474">rust-lang/rust#44494</a> and <a href="https://github.com/rust-lang/rust/issues/28237#issuecomment-363374130">rust-lang/rust#28237</a> (these links |
| will bring you directly to the comment containing the stabilization report).</p> |
| <h2 id="fcp"><a class="header" href="#fcp">FCP</a></h2> |
| <p>If any member of the team responsible for tracking this |
| feature agrees with stabilizing this feature, they will |
| start the FCP (final-comment-period) process by commenting</p> |
| <pre><code class="language-text">@rfcbot fcp merge |
| </code></pre> |
| <p>The rest of the team members will review the proposal. If the final |
| decision is to stabilize, we proceed to do the actual code modification.</p> |
| <h2 id="stabilization-pr"><a class="header" href="#stabilization-pr">Stabilization PR</a></h2> |
| <p>Once we have decided to stabilize a feature, we need to have |
| a PR that actually makes that stabilization happen. These kinds |
| of PRs are a great way to get involved in Rust, as they take |
| you on a little tour through the source code.</p> |
| <p>Here is a general guide to how to stabilize a feature -- |
| every feature is different, of course, so some features may |
| require steps beyond what this guide talks about.</p> |
| <p>Note: Before we stabilize any feature, it's the rule that it |
| should appear in the documentation.</p> |
| <h3 id="updating-the-feature-gate-listing"><a class="header" href="#updating-the-feature-gate-listing">Updating the feature-gate listing</a></h3> |
| <p>There is a central listing of feature-gates in |
| <a href="https://doc.rust-lang.org/nightly/nightly-rustc/rustc_feature/index.html"><code>compiler/rustc_feature</code></a>. Search for the <code>declare_features!</code> |
| macro. There should be an entry for the feature you are aiming |
| to stabilize, something like (this example is taken from |
| <a href="https://github.com/rust-lang/rust/issues/32409">rust-lang/rust#32409</a>:</p> |
| <pre><code class="language-rust ignore">// pub(restricted) visibilities (RFC 1422) |
| (active, pub_restricted, "1.9.0", Some(32409)), |
| </code></pre> |
| <p>The above line should be moved down to the area for "accepted" |
| features, declared below in a separate call to <code>declare_features!</code>. |
| When it is done, it should look like:</p> |
| <pre><code class="language-rust ignore">// pub(restricted) visibilities (RFC 1422) |
| (accepted, pub_restricted, "1.31.0", Some(32409)), |
| // note that we changed this |
| </code></pre> |
| <p>Note that, the version number is updated to be the version number |
| of the stable release where this feature will appear. This can be |
| found by consulting <a href="https://forge.rust-lang.org/">the forge</a>, which will guide |
| you the next stable release number. You want to add 1 to that, |
| because the code that lands today will become go into beta on that |
| date, and then become stable after that. So, at the time of this |
| writing, the next stable release (i.e. what is currently beta) was |
| 1.30.0, hence I wrote 1.31.0 above.</p> |
| <h3 id="removing-existing-uses-of-the-feature-gate"><a class="header" href="#removing-existing-uses-of-the-feature-gate">Removing existing uses of the feature-gate</a></h3> |
| <p>Next search for the feature string (in this case, <code>pub_restricted</code>) |
| in the codebase to find where it appears. Change uses of |
| <code>#![feature(XXX)]</code> from the <code>std</code> and any rustc crates to be |
| <code>#![cfg_attr(bootstrap, feature(XXX))]</code>. This includes the feature-gate |
| only for stage0, which is built using the current beta (this is |
| needed because the feature is still unstable in the current beta).</p> |
| <p>Also, remove those strings from any tests. If there are tests |
| specifically targeting the feature-gate (i.e., testing that the |
| feature-gate is required to use the feature, but nothing else), |
| simply remove the test.</p> |
| <h3 id="do-not-require-the-feature-gate-to-use-the-feature"><a class="header" href="#do-not-require-the-feature-gate-to-use-the-feature">Do not require the feature-gate to use the feature</a></h3> |
| <p>Most importantly, remove the code which flags an error if the |
| feature-gate is not present (since the feature is now considered |
| stable). If the feature can be detected because it employs some |
| new syntax, then a common place for that code to be is in the |
| same <code>compiler/rustc_ast_passes/src/feature_gate.rs</code>. |
| For example, you might see code like this:</p> |
| <pre><code class="language-rust ignore">gate_feature_post!(&self, pub_restricted, span, |
| "`pub(restricted)` syntax is experimental"); |
| </code></pre> |
| <p>This <code>gate_feature_post!</code> macro prints an error if the |
| <code>pub_restricted</code> feature is not enabled. It is not needed |
| now that <code>#[pub_restricted]</code> is stable.</p> |
| <p>For more subtle features, you may find code like this:</p> |
| <pre><code class="language-rust ignore">if self.tcx.sess.features.borrow().pub_restricted { /* XXX */ } |
| </code></pre> |
| <p>This <code>pub_restricted</code> field (obviously named after the feature) |
| would ordinarily be false if the feature flag is not present |
| and true if it is. So transform the code to assume that the field |
| is true. In this case, that would mean removing the <code>if</code> and |
| leaving just the <code>/* XXX */</code>.</p> |
| <pre><code class="language-rust ignore">if self.tcx.sess.features.borrow().pub_restricted { /* XXX */ } |
| becomes |
| /* XXX */ |
| |
| if self.tcx.sess.features.borrow().pub_restricted && something { /* XXX */ } |
| becomes |
| if something { /* XXX */ } |
| </code></pre> |
| |
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