rust-analyzer/README.md

Rust Analyzer

Rust Analyzer is an experimental modular compiler frontend for the Rust language, which aims to lay a foundation for excellent IDE support.

It doesn't implement much of compiler functionality yet, but the white-space preserving Rust parser works, and there are significant chunks of overall architecture (indexing, on-demand & lazy computation, snapshotable world view) in place. Some basic IDE functionality is provided via a language server.

Quick Start

Rust analyzer builds on stable Rust >= 1.29.0.

# run tests
$ cargo test

# show syntax tree of a Rust file
$ cargo run --package ra_cli parse < crates/ra_syntax/src/lib.rs

# show symbols of a Rust file
$ cargo run --package ra_cli symbols < crates/ra_syntax/src/lib.rs

To try out the language server, see these instructions. Please note that the server is not ready for general use yet. If you are looking for a Rust IDE that works, use IntelliJ Rust or RLS. That being said, the basic stuff works, and rust analyzer is developed in the rust analyzer powered editor.

Current Status and Plans

Rust analyzer aims to fill the same niche as the official Rust Language Server, but uses a significantly different architecture. More details can be found in this thread, but the core issue is that RLS works in the "wait until user stops typing, run the build process, save the results of the analysis" mode, which arguably is the wrong foundation for IDE.

Rust Analyzer is a hobby project at the moment, there's exactly zero guarantees that it becomes production-ready one day.

The near/mid term plan is to work independently of the main rustc compiler and implement at least simplistic versions of name resolution, macro expansion and type inference. The purpose is two fold:

• to quickly bootstrap usable and useful language server: solution that covers 80% of Rust code will be useful for IDEs, and will be vastly simpler than 100% solution.

• to understand how the consumer-side of compiler API should look like (especially it's on-demand aspects). If you have get_expression_type function, you can write a ton of purely-IDE features on top of it, even if the function is only partially correct. Plugin in the precise function afterwards should just make IDE features more reliable.

The long term plan is to merge with the mainline rustc compiler, probably around the HIR boundary? That is, use rust analyzer for parsing, macro expansion and related bits of name resolution, but leave the rest (including type inference and trait selection) to the existing rustc.

Code Walk-Through

crates/ra_syntax

Rust syntax tree structure and parser. See RFC for some design notes.

• yellow, red/green syntax tree, heavily inspired by this
• grammar, the actual parser
• parser_api/parser_impl bridges the tree-agnostic parser from grammar with yellow trees
• grammar.ron RON description of the grammar, which is used to generate syntax_kinds and ast modules.
• algo: generic tree algorithms, including walk for O(1) stack space tree traversal (this is cool) and visit for type-driven visiting the nodes (this is double plus cool, if you understand how Visitor works, you understand rust-analyzer).

crates/ra_editor

All IDE features which can be implemented if you only have access to a single file. ra_editor could be used to enhance editing of Rust code without the need to fiddle with build-systems, file synchronization and such.

In a sense, ra_editor is just a bunch of pure functions which take a syntax tree as an input.

crates/salsa

An implementation of red-green incremental compilation algorithm from rust compiler. It makes all rust-analyzer features on-demand.

crates/ra_analysis

A stateful library for analyzing many Rust files as they change. AnalysisHost is a mutable entity (clojure's atom) which holds current state, incorporates changes and handles out Analysis --- an immutable consistent snapshot of world state at a point in time, which actually powers analysis.

crates/ra_lsp_server

An LSP implementation which uses ra_analysis for managing state and ra_editor for actually doing useful stuff.

crates/cli

A CLI interface to libsyntax

crate/tools

Code-gen tasks, used to develop rust-analyzer:

• cargo gen-kinds -- generate ast and syntax_kinds
• cargo gen-tests -- collect inline tests from grammar
• cargo install-code -- build and install VS Code extension and server

editors/code

VS Code plugin

Performance

Non-incremental, but seems pretty fast:

$ cargo build --release --package ra_cli
$ wc -l ~/projects/rust/src/libsyntax/parse/parser.rs
7546 /home/matklad/projects/rust/src/libsyntax/parse/parser.rs
$ ./target/release/ra_cli parse < ~/projects/rust/src/libsyntax/parse/parser.rs --no-dump  > /dev/null
parsing: 21.067065ms

Getting in touch

@matklad can be found at Rust discord, in #ides-and-editors.

License

Rust analyzer is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0).

See LICENSE-APACHE and LICENSE-MIT for details.