Reference

Quick reference material for files and configuration scattered across the repository.

Pages in this section

• Configuration — bootstrap.toml, rustfmt.toml, triagebot.toml, rust-bors.toml, typos.toml, REUSE.toml
• Dependencies — workspace structure, allowed crates.io deps, vendored subtrees and submodules

Conventions cheat sheet

You're looking for…	Path
Build system	src/bootstrap/ + x.py
Build options docs	bootstrap.example.toml
The compiler	compiler/ (~70 rustc_* crates)
The standard library	library/
The default test suite	tests/
Reference docs (the Reference book)	src/doc/reference/ (submodule)
The rustc dev guide	src/doc/rustc-dev-guide/ (subtree)
The Rust Book	src/doc/book/ (submodule)
Release notes	RELEASES.md
Stage 0 pin	src/stage0
Default branch / merge queue	rust-bors.toml
PR automation	triagebot.toml
CI manifest	.github/workflows/ci.yml + src/ci/

Common file types

File type	Where	Used by
Cargo.toml	Workspace root + every crate	Cargo
Cargo.lock	Workspace root + library/	Cargo (locked)
*.ftl	Each compiler/rustc_*/messages.ftl	Diagnostic translation
*.rs	Source code	Rust compilation
*.stderr / *.stdout	tests/ui/	UI test snapshots
*.mir	tests/mir-opt/	MIR-opt test snapshots
*.toml	Config files	bootstrap, rustfmt, triagebot, rust-bors, typos, REUSE
rmake.rs	tests/run-make/<dir>/	run-make tests

Useful entry points

For a new contributor approaching a particular subsystem:

• Compiler frontend → compiler/rustc_parse/, compiler/rustc_resolve/
• Type system → compiler/rustc_middle/src/ty/
• Borrow checker → compiler/rustc_borrowck/
• MIR optimizations → compiler/rustc_mir_transform/src/passes/
• Standard library → library/std/src/, library/core/src/
• Build system → src/bootstrap/src/
• Tests → tests/ui/, tests/run-make/
• CI → src/ci/, .github/workflows/ci.yml