Tooling

Tools shipped in this repository for contributors. Tools that ship as part of the Rust distribution (rustdoc, miri, clippy, rustfmt, rust-analyzer) are documented under Tools.

Build system: x

x, x.ps1, and x.py are wrappers that find a Python interpreter and call src/bootstrap/bootstrap.py. That script downloads the stage 0 toolchain (cached under build/cache/) and uses it to compile the Rust-based bootstrap binary, which then drives Cargo to build everything else. See Bootstrap for the full flow.

Configuration lives in bootstrap.toml; the documented options live in bootstrap.example.toml and the parser in src/bootstrap/src/core/config/.

Repo lints: tidy

src/tools/tidy/ is the project's repo-wide linter. It runs as ./x test tidy and checks:

• License headers and REUSE.toml consistency
• Alphabetical ordering of marked lists
• File-size thresholds
• Banned external dependencies (extdeps.rs)
• Trailing whitespace, tabs, line-length
• Several other consistency checks

If tidy fails, the failure message tells you exactly which check tripped. Most are auto-fixable.

Formatting: rustfmt

./x fmt runs the in-tree rustfmt across the workspace using rustfmt.toml. The configuration is more conservative than upstream rustfmt's defaults (e.g., it disables some aggressive comment reformatting) and is enforced on all compiler/, library/, and src/ Rust code.

Linting: clippy

./x clippy runs the in-tree clippy. Clippy is a subtree from rust-lang/rust-clippy at src/tools/clippy/. New rustc PRs do not have to be clippy-clean (the codebase has many intentional #[allow]s in performance-critical spots), but new code should not regress clippy.

Typo detection: typos

typos.toml configures the typos tool, which catches misspellings. CI runs it; you can run it locally with cargo install typos-cli && typos.

Test runner: compiletest

src/tools/compiletest/ parses the directives at the top of each test file (//@ compile-flags: …) and runs rustc with the right inputs, comparing output against .stderr / .stdout snapshots. See Testing.

Bootstrap helpers

A long tail of helper crates lives under src/tools/:

• build-manifest — generates the release manifests
• bump-stage0 — updates src/stage0 with a new beta
• generate-copyright — produces COPYRIGHT-thirdparty.md
• linkchecker — finds broken links in built docs
• html-checker — HTML validation for rustdoc output
• unicode-table-generator — regenerates Unicode tables in core::unicode
• replace-version-placeholder — used at release-cut to replace CURRENT_RUSTC_VERSION strings

Editor and IDE setup

• rust-analyzer — the canonical IDE backend, vendored as a submodule. Configure it on compiler/rustc/Cargo.toml to get IDE features inside the compiler tree (the rustc.json profile created by ./x setup does this).
• ./x setup can install a git pre-push hook that runs tidy + format check, catching the most common CI failures locally.

CI: GitHub Actions + Docker

Top-level CI is GitHub Actions (.github/workflows/ci.yml) but most jobs delegate to Docker images defined in src/ci/docker/ and run via src/ci/run.sh. Job orchestration is done in Rust by the citool binary.

The CI matrix covers:

• All tier 1 platforms (Linux, macOS, Windows, multiple architectures)
• Cross-compilation builds for many tier 2 targets
• Special configurations: ASan, MSan, TSan, debug-assertions, coverage
• Documentation builds
• Tooling tests (rustfmt, clippy, miri, rustdoc-gui)

Each PR runs a fast subset on push; the merge queue runs the full matrix. The complete CI manifest is generated by citool.

Bots and merge automation

Bot	Where configured	What it does
bors / rust-bors	rust-bors.toml	Merge queue
triagebot	triagebot.toml	PR assignment, labels, FCP, ping groups, glossary mentions
rustbot	(server-side)	Rollups, status pings
renovate	.github/renovate.json5	npm/JS deps
dependabot	(server-side)	Security advisories

If a bot misbehaves, the team contact is T-infra on Zulip.

Performance tooling

• rustc-perf — the benchmark suite. Submodule at src/tools/rustc-perf/.
• -Zself-profile — built into rustc. Pair with the summarize tool from measureme.
• cargo-bisect-rustc — for regression bisection.

Documentation builds

./x doc builds:

• The Rust Book (src/doc/book/ — submodule)
• The Reference (src/doc/reference/ — submodule)
• The Rustonomicon (src/doc/nomicon/ — submodule)
• The rustc dev guide (src/doc/rustc-dev-guide/ — subtree)
• rustdoc for core, alloc, std, proc_macro, etc.
• The unstable book (src/doc/unstable-book/ — generated)
• Edition guide, embedded book, error index

Each book is built with rustbook, a thin wrapper around mdBook.