#syntax #whitespace #parser #compiler #front-end #experimental


Comment and whitespace preserving parser for the Rust langauge

1 unstable release

0.1.0 Nov 5, 2018
Download history 5/week @ 2018-11-12 2/week @ 2018-11-19 9/week @ 2018-11-26 6/week @ 2018-12-03 6/week @ 2018-12-10 4/week @ 2018-12-17 6/week @ 2018-12-24 1/week @ 2018-12-31 4/week @ 2019-01-07 3/week @ 2019-01-14 1/week @ 2019-01-21 2/week @ 2019-01-28 3/week @ 2019-02-11 1/week @ 2019-02-18

1 downloads per month



Rust Analyzer

Build Status

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.

Work on the Rust Analyzer is sponsored by

Ferrous Systems

Quick Start

Rust analyzer builds on Rust >= 1.31.0 and uses the 2018 edition.

# 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

# install the language server
$ cargo install-lsp
$ cargo install --path crates/ra_lsp_server

See these instructions for VS Code setup and the list of features (some of which are VS Code specific).


See these instructions on how to debug the vscode extension and the lsp server.

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 an experimental 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. Pluging 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.

Supported LSP features



Text Synchronization


Lanuguage Features

Getting in touch

We have a Discord server dedicated to compilers and language servers implemented in Rust: https://discord.gg/sx3RQZB.




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



~25K SLoC