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User Manual

At its core, rust-analyzer is a library for semantic analysis of Rust code as it changes over time. This manual focuses on a specific usage of the library — running it as part of a server that implements the Language Server Protocol (LSP). The LSP allows various code editors, like VS Code, Emacs or Vim, to implement semantic features like completion or goto definition by talking to an external language server process.

Tip

To improve this document, send a pull request:
https://github.com/rust-analyzer/…​/manual.adoc

The manual is written in AsciiDoc and includes some extra files which are generated from the source code. Run cargo test and cargo xtask codegen to create these and then asciidoctor manual.adoc to create an HTML copy.

If you have questions about using rust-analyzer, please ask them in the “IDEs and Editors” topic of Rust users forum.

Table of Contents

Installation

In theory, one should be able to just install the rust-analyzer binary and have it automatically work with any editor. We are not there yet, so some editor specific setup is required.

Additionally, rust-analyzer needs the sources of the standard library. If the source code is not present, rust-analyzer will attempt to install it automatically.

To add the sources manually, run the following command:

$ rustup component add rust-src

Toolchain

Only the latest stable standard library source is officially supported for use with rust-analyzer. If you are using an older toolchain or have an override set, rust-analyzer may fail to understand the Rust source. You will either need to update your toolchain or use an older version of rust-analyzer that is compatible with your toolchain.

If you are using an override in your project, you can still force rust-analyzer to use the stable toolchain via the environment variable RUSTUP_TOOLCHAIN. For example, with VS Code or coc-rust-analyzer:

{ "rust-analyzer.server.extraEnv": { "RUSTUP_TOOLCHAIN": "stable" } }

VS Code

This is the best supported editor at the moment. The rust-analyzer plugin for VS Code is maintained in tree.

You can install the latest release of the plugin from the marketplace.

Note that the plugin may cause conflicts with the previous official Rust plugin. The latter is no longer maintained and should be uninstalled.

The server binary is stored in the extension install directory, which starts with rust-lang.rust-analyzer- and is located under:

  • Linux: ~/.vscode/extensions

  • Linux (Remote, such as WSL): ~/.vscode-server/extensions

  • macOS: ~/.vscode/extensions

  • Windows: %USERPROFILE%\.vscode\extensions

As an exception, on NixOS, the extension makes a copy of the server and stores it under ~/.config/Code/User/globalStorage/rust-lang.rust-analyzer.

Note that we only support the two most recent versions of VS Code.

Updates

The extension will be updated automatically as new versions become available. It will ask your permission to download the matching language server version binary if needed.

Nightly

We ship nightly releases for VS Code. To help us out by testing the newest code, you can enable pre-release versions in the Code extension page.

Manual installation

Alternatively, download a VSIX corresponding to your platform from the releases page.

Install the extension with the Extensions: Install from VSIX command within VS Code, or from the command line via:

$ code --install-extension /path/to/rust-analyzer.vsix

If you are running an unsupported platform, you can install rust-analyzer-no-server.vsix and compile or obtain a server binary. Copy the server anywhere, then add the path to your settings.json, for example:

{ "rust-analyzer.server.path": "~/.local/bin/rust-analyzer-linux" }

Building From Source

Both the server and the Code plugin can be installed from source:

$ git clone https://github.com/rust-lang/rust-analyzer.git && cd rust-analyzer
$ cargo xtask install

You’ll need Cargo, nodejs (matching a supported version of VS Code) and npm for this.

Note that installing via xtask install does not work for VS Code Remote, instead you’ll need to install the .vsix manually.

If you’re not using Code, you can compile and install only the LSP server:

$ cargo xtask install --server

Make sure that .cargo/bin is in $PATH and precedes paths where rust-analyzer may also be installed. Specifically, rustup includes a proxy called rust-analyzer, which can cause problems if you’re planning to use a source build or even a downloaded binary.

rust-analyzer Language Server Binary

Other editors generally require the rust-analyzer binary to be in $PATH. You can download pre-built binaries from the releases page. You will need to uncompress and rename the binary for your platform, e.g. from rust-analyzer-aarch64-apple-darwin.gz on Mac OS to rust-analyzer, make it executable, then move it into a directory in your $PATH.

On Linux to install the rust-analyzer binary into ~/.local/bin, these commands should work:

$ mkdir -p ~/.local/bin
$ curl -L https://github.com/rust-lang/rust-analyzer/releases/latest/download/rust-analyzer-x86_64-unknown-linux-gnu.gz | gunzip -c - > ~/.local/bin/rust-analyzer
$ chmod +x ~/.local/bin/rust-analyzer

Make sure that ~/.local/bin is listed in the $PATH variable and use the appropriate URL if you’re not on a x86-64 system.

You don’t have to use ~/.local/bin, any other path like ~/.cargo/bin or /usr/local/bin will work just as well.

Alternatively, you can install it from source using the command below. You’ll need the latest stable version of the Rust toolchain.

$ git clone https://github.com/rust-lang/rust-analyzer.git && cd rust-analyzer
$ cargo xtask install --server

If your editor can’t find the binary even though the binary is on your $PATH, the likely explanation is that it doesn’t see the same $PATH as the shell, see this issue. On Unix, running the editor from a shell or changing the .desktop file to set the environment should help.

rustup

rust-analyzer is available in rustup:

$ rustup component add rust-analyzer

Arch Linux

The rust-analyzer binary can be installed from the repos or AUR (Arch User Repository):

Install it with pacman, for example:

$ pacman -S rust-analyzer

Gentoo Linux

There are two ways to install rust-analyzer under Gentoo:

  • when installing dev-lang/rust or dev-lang/rust-bin, enable the rust-analyzer and rust-src USE flags

  • use the rust-analyzer component in rustup (see instructions above)

Note that in both cases, the version installed lags for a couple of months behind the official releases on GitHub. To obtain a newer one, you can download a binary from GitHub Releases or building from source.

macOS

The rust-analyzer binary can be installed via Homebrew.

$ brew install rust-analyzer

VS Code or VSCodium in Flatpak

Setting up rust-analyzer with a Flatpak version of Code is not trivial because of the Flatpak sandbox. While the sandbox can be disabled for some directories, /usr/bin will always be mounted under /run/host/usr/bin. This prevents access to the system’s C compiler, a system-wide installation of Rust, or any other libraries you might want to link to. Some compilers and libraries can be acquired as Flatpak SDKs, such as org.freedesktop.Sdk.Extension.rust-stable or org.freedesktop.Sdk.Extension.llvm15.

If you use a Flatpak SDK for Rust, it must be in your PATH:

  • install the SDK extensions with flatpak install org.freedesktop.Sdk.Extension.{llvm15,rust-stable}//23.08

  • enable SDK extensions in the editor with the environment variable FLATPAK_ENABLE_SDK_EXT=llvm15,rust-stable (this can be done using flatseal or flatpak override)

If you want to use Flatpak in combination with rustup, the following steps might help:

  • both Rust and rustup have to be installed using https://rustup.rs. Distro packages will not work.

  • you need to launch Code, open a terminal and run echo $PATH

  • using Flatseal, you must add an environment variable called PATH. Set its value to the output from above, appending :~/.cargo/bin, where ~ is the path to your home directory. You must replace ~, as it won’t be expanded otherwise.

  • while Flatseal is open, you must enable access to "All user files"

A C compiler should already be available via org.freedesktop.Sdk. Any other tools or libraries you will need to acquire from Flatpak.

Emacs

Prerequisites: You have installed the rust-analyzer binary.

To use rust-analyzer, you need to install and enable one of the two popular LSP client implementations for Emacs, Eglot or LSP Mode. Both enable rust-analyzer by default in rust buffers if it is available.

Eglot

Eglot is the more minimalistic and lightweight LSP client for Emacs, integrates well with existing Emacs functionality and is built into Emacs starting from release 29.

After installing Eglot, e.g. via M-x package-install (not needed from Emacs 29), you can enable it via the M-x eglot command or load it automatically in rust-mode via

(add-hook 'rust-mode-hook 'eglot-ensure)

To enable clippy, you will need to configure the initialization options to pass the check.command setting.

(add-to-list 'eglot-server-programs
             '((rust-ts-mode rust-mode) .
               ("rust-analyzer" :initializationOptions (:check (:command "clippy")))))

For more detailed instructions and options see the Eglot manual (also available from Emacs via M-x info) and the Eglot readme.

Eglot does not support the rust-analyzer extensions to the language-server protocol and does not aim to do so in the future. The eglot-x package adds experimental support for those LSP extensions.

LSP Mode

LSP-mode is the original LSP-client for emacs. Compared to Eglot it has a larger codebase and supports more features, like LSP protocol extensions. With extension packages like LSP UI it offers a lot of visual eyecandy. Further it integrates well with DAP mode for support of the Debug Adapter Protocol.

You can install LSP-mode via M-x package-install and then run it via the M-x lsp command or load it automatically in rust buffers with

(add-hook 'rust-mode-hook 'lsp-deferred)

For more information on how to set up LSP mode and its extension package see the instructions in the LSP mode manual. Also see the rust-analyzer section for rust-analyzer specific options and commands, which you can optionally bind to keys.

Note the excellent guide from @rksm on how to set-up Emacs for Rust development with LSP mode and several other packages.

Vim/Neovim

Prerequisites: You have installed the rust-analyzer binary. Not needed if the extension can install/update it on its own, coc-rust-analyzer is one example.

There are several LSP client implementations for Vim or Neovim:

coc-rust-analyzer

  1. Install coc.nvim by following the instructions at coc.nvim (Node.js required)

  2. Run :CocInstall coc-rust-analyzer to install coc-rust-analyzer, this extension implements most of the features supported in the VSCode extension:

    • automatically install and upgrade stable/nightly releases

    • same configurations as VSCode extension, rust-analyzer.server.path, rust-analyzer.cargo.features etc.

    • same commands too, rust-analyzer.analyzerStatus, rust-analyzer.ssr etc.

    • inlay hints for variables and method chaining, Neovim Only

Note: for code actions, use coc-codeaction-cursor and coc-codeaction-selected; coc-codeaction and coc-codeaction-line are unlikely to be useful.

LanguageClient-neovim

  1. Install LanguageClient-neovim by following the instructions here

    • The GitHub project wiki has extra tips on configuration

  2. Configure by adding this to your Vim/Neovim config file (replacing the existing Rust-specific line if it exists):

    let g:LanguageClient_serverCommands = {
\ 'rust': ['rust-analyzer'],
\ }

YouCompleteMe

Install YouCompleteMe by following the instructions here.

rust-analyzer is the default in ycm, it should work out of the box.

ALE

To use the LSP server in ale:

let g:ale_linters = {'rust': ['analyzer']}

nvim-lsp

Neovim 0.5 has built-in language server support. For a quick start configuration of rust-analyzer, use neovim/nvim-lspconfig. Once neovim/nvim-lspconfig is installed, use lua require'lspconfig'.rust_analyzer.setup({}) in your init.vim.

You can also pass LSP settings to the server:

lua << EOF
local lspconfig = require'lspconfig'

local on_attach = function(client)
    require'completion'.on_attach(client)
end

lspconfig.rust_analyzer.setup({
    on_attach = on_attach,
    settings = {
        ["rust-analyzer"] = {
            imports = {
                granularity = {
                    group = "module",
                },
                prefix = "self",
            },
            cargo = {
                buildScripts = {
                    enable = true,
                },
            },
            procMacro = {
                enable = true
            },
        }
    }
})
EOF

If you’re running Neovim 0.10 or later, you can enable inlay hints via on_attach:

lspconfig.rust_analyzer.setup({
    on_attach = function(client, bufnr)
        vim.lsp.inlay_hint.enable(true, { bufnr = bufnr })
    end
})

Note that the hints are only visible after rust-analyzer has finished loading and you have to edit the file to trigger a re-render.

See https://sharksforarms.dev/posts/neovim-rust/ for more tips on getting started.

Check out https://github.com/mrcjkb/rustaceanvim for a batteries included rust-analyzer setup for Neovim.

vim-lsp

vim-lsp is installed by following the plugin instructions. It can be as simple as adding this line to your .vimrc:

Plug 'prabirshrestha/vim-lsp'

Next you need to register the rust-analyzer binary. If it is available in $PATH, you may want to add this to your .vimrc:

if executable('rust-analyzer')
  au User lsp_setup call lsp#register_server({
        \   'name': 'Rust Language Server',
        \   'cmd': {server_info->['rust-analyzer']},
        \   'whitelist': ['rust'],
        \ })
endif

There is no dedicated UI for the server configuration, so you would need to send any options as a value of the initialization_options field, as described in the Configuration section. Here is an example of how to enable the proc-macro support:

if executable('rust-analyzer')
  au User lsp_setup call lsp#register_server({
        \   'name': 'Rust Language Server',
        \   'cmd': {server_info->['rust-analyzer']},
        \   'whitelist': ['rust'],
        \   'initialization_options': {
        \     'cargo': {
        \       'buildScripts': {
        \         'enable': v:true,
        \       },
        \     },
        \     'procMacro': {
        \       'enable': v:true,
        \     },
        \   },
        \ })
endif

Sublime Text

Sublime Text 4:

Note
 Install LSP-file-watcher-chokidar to enable file watching (workspace/didChangeWatchedFiles).

Sublime Text 3:

If it worked, you should see "rust-analyzer, Line X, Column Y" on the left side of the status bar, and after waiting a bit, functionalities like tooltips on hovering over variables should become available.

If you get an error saying No such file or directory: 'rust-analyzer', see the rust-analyzer binary section on installing the language server binary.

GNOME Builder

GNOME Builder 3.37.1 and newer has native rust-analyzer support. If the LSP binary is not available, GNOME Builder can install it when opening a Rust file.

Eclipse IDE

Support for Rust development in the Eclipse IDE is provided by Eclipse Corrosion. If available in PATH or in some standard location, rust-analyzer is detected and powers editing of Rust files without further configuration. If rust-analyzer is not detected, Corrosion will prompt you for configuration of your Rust toolchain and language server with a link to the Window > Preferences > Rust preference page; from here a button allows to download and configure rust-analyzer, but you can also reference another installation. You’ll need to close and reopen all .rs and Cargo files, or to restart the IDE, for this change to take effect.

Kate Text Editor

Support for the language server protocol is built into Kate through the LSP plugin, which is included by default. It is preconfigured to use rust-analyzer for Rust sources since Kate 21.12.

To change rust-analyzer config options, start from the following example and put it into Kate’s "User Server Settings" tab (located under the LSP Client settings):

{
    "servers": {
        "rust": {
            "initializationOptions": {
                "cachePriming": {
                    "enable": false
                },
                "check": {
                    "allTargets": false
                },
                "checkOnSave": false
            }
        }
    }
}

Then click on apply, and restart the LSP server for your rust project.

juCi++

juCi++ has built-in support for the language server protocol, and since version 1.7.0 offers installation of both Rust and rust-analyzer when opening a Rust file.

Kakoune

Kakoune supports LSP with the help of kak-lsp. Follow the instructions to install kak-lsp. To configure kak-lsp, refer to the configuration section which is basically about copying the configuration file in the right place (latest versions should use rust-analyzer by default).

Finally, you need to configure Kakoune to talk to kak-lsp (see Usage section). A basic configuration will only get you LSP but you can also activate inlay diagnostics and auto-formatting on save. The following might help you get all of this.

eval %sh{kak-lsp --kakoune -s $kak_session}  # Not needed if you load it with plug.kak.
hook global WinSetOption filetype=rust %{
    # Enable LSP
    lsp-enable-window

    # Auto-formatting on save
    hook window BufWritePre .* lsp-formatting-sync

    # Configure inlay hints (only on save)
    hook window -group rust-inlay-hints BufWritePost .* rust-analyzer-inlay-hints
    hook -once -always window WinSetOption filetype=.* %{
        remove-hooks window rust-inlay-hints
    }
}

Helix

Helix supports LSP by default. However, it won’t install rust-analyzer automatically. You can follow instructions for installing rust-analyzer binary.

Visual Studio 2022

There are multiple rust-analyzer extensions for Visual Studio 2022 on Windows:

rust-analyzer.vs

(License: Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International)

Support for Rust development in the Visual Studio IDE is enabled by the rust-analyzer package. Either click on the download link or install from IDE’s extension manager. For now Visual Studio 2022 is required. All editions are supported viz. Community, Professional & Enterprise. The package aims to provide 0-friction installation and therefore comes loaded with most things required including rust-analyzer binary. If anything it needs is missing, appropriate errors / warnings will guide the user. E.g. cargo.exe needs to be in path and the package will tell you as much. This package is under rapid active development. So if you encounter any issues please file it at rust-analyzer.vs.

VS_RustAnalyzer

(License: GPL)

SourceGear Rust

(License: closed source)

  • Free (no-cost)

  • Supports all editions of Visual Studio 2022 on Windows: Community, Professional, or Enterprise

Lapce

Lapce has a Rust plugin which you can install directly. Unfortunately, it downloads an old version of rust-analyzer, but you can set the server path under Settings.

Crates

There is a package named ra_ap_rust_analyzer available on crates.io, for someone who wants to use it programmatically.

For more details, see the publish workflow.

Zed

Zed has native rust-analyzer support. If the LSP binary is not available, Zed can install it when opening a Rust file.

Troubleshooting

Start with looking at the rust-analyzer version. Try rust-analyzer: Show RA Version in VS Code (using Command Palette feature typically activated by Ctrl+Shift+P) or rust-analyzer --version in the command line. If the date is more than a week ago, it’s better to update rust-analyzer version.

The next thing to check would be panic messages in rust-analyzer’s log. Log messages are printed to stderr, in VS Code you can see them in the Output > Rust Analyzer Language Server tab of the panel. To see more logs, set the RA_LOG=info environment variable, this can be done either by setting the environment variable manually or by using rust-analyzer.server.extraEnv, note that both of these approaches require the server to be restarted.

To fully capture LSP messages between the editor and the server, run the rust-analyzer: Toggle LSP Logs command and check Output > Rust Analyzer Language Server Trace.

The root cause for many “nothing works” problems is that rust-analyzer fails to understand the project structure. To debug that, first note the rust-analyzer section in the status bar. If it has an error icon and red, that’s the problem (hover will have somewhat helpful error message). rust-analyzer: Status prints dependency information for the current file. Finally, RA_LOG=project_model=debug enables verbose logs during project loading.

If rust-analyzer outright crashes, try running rust-analyzer analysis-stats /path/to/project/directory/ on the command line. This command type checks the whole project in batch mode bypassing LSP machinery.

When filing issues, it is useful (but not necessary) to try to minimize examples. An ideal bug reproduction looks like this:

$ git clone https://github.com/username/repo.git && cd repo && git switch --detach commit-hash
$ rust-analyzer --version
rust-analyzer dd12184e4 2021-05-08 dev
$ rust-analyzer analysis-stats .
💀 💀 💀

It is especially useful when the repo doesn’t use external crates or the standard library.

If you want to go as far as to modify the source code to debug the problem, be sure to take a look at the dev docs!

Configuration

Source: config.rs

The Installation section contains details on configuration for some of the editors. In general rust-analyzer is configured via LSP messages, which means that it’s up to the editor to decide on the exact format and location of configuration files.

Some clients, such as VS Code or COC plugin in Vim provide rust-analyzer specific configuration UIs. Others may require you to know a bit more about the interaction with rust-analyzer.

For the later category, it might help to know that the initial configuration is specified as a value of the initializationOptions field of the InitializeParams message, in the LSP protocol. The spec says that the field type is any?, but rust-analyzer is looking for a JSON object that is constructed using settings from the list below. Name of the setting, ignoring the rust-analyzer. prefix, is used as a path, and value of the setting becomes the JSON property value.

For example, a very common configuration is to enable proc-macro support, can be achieved by sending this JSON:

{
  "cargo": {
    "buildScripts": {
      "enable": true,
    },
  },
  "procMacro": {
    "enable": true,
  }
}

Please consult your editor’s documentation to learn more about how to configure LSP servers.

To verify which configuration is actually used by rust-analyzer, set RA_LOG environment variable to rust_analyzer=info and look for config-related messages. Logs should show both the JSON that rust-analyzer sees as well as the updated config.

This is the list of config options rust-analyzer supports:

Non-Cargo Based Projects

rust-analyzer does not require Cargo. However, if you use some other build system, you’ll have to describe the structure of your project for rust-analyzer in the rust-project.json format:

interface JsonProject {
    /// Path to the sysroot directory.
    ///
    /// The sysroot is where rustc looks for the
    /// crates that are built-in to rust, such as
    /// std.
    ///
    /// https://doc.rust-lang.org/rustc/command-line-arguments.html#--sysroot-override-the-system-root
    ///
    /// To see the current value of sysroot, you
    /// can query rustc:
    ///
    /// ```
    /// $ rustc --print sysroot
    /// /Users/yourname/.rustup/toolchains/stable-x86_64-apple-darwin
    /// ```
    sysroot?: string;
    /// Path to the directory with *source code* of
    /// sysroot crates.
    ///
    /// By default, this is `lib/rustlib/src/rust/library`
    /// relative to the sysroot.
    ///
    /// It should point to the directory where std,
    /// core, and friends can be found:
    ///
    /// https://github.com/rust-lang/rust/tree/master/library.
    ///
    /// If provided, rust-analyzer automatically adds
    /// dependencies on sysroot crates. Conversely,
    /// if you omit this path, you can specify sysroot
    /// dependencies yourself and, for example, have
    /// several different "sysroots" in one graph of
    /// crates.
    sysroot_src?: string;
    /// The set of crates comprising the current
    /// project. Must include all transitive
    /// dependencies as well as sysroot crate (libstd,
    /// libcore and such).
    crates: Crate[];
}

interface Crate {
    /// Optional crate name used for display purposes,
    /// without affecting semantics. See the `deps`
    /// key for semantically-significant crate names.
    display_name?: string;
    /// Path to the root module of the crate.
    root_module: string;
    /// Edition of the crate.
    edition: "2015" | "2018" | "2021";
    /// Dependencies
    deps: Dep[];
    /// Should this crate be treated as a member of
    /// current "workspace".
    ///
    /// By default, inferred from the `root_module`
    /// (members are the crates which reside inside
    /// the directory opened in the editor).
    ///
    /// Set this to `false` for things like standard
    /// library and 3rd party crates to enable
    /// performance optimizations (rust-analyzer
    /// assumes that non-member crates don't change).
    is_workspace_member?: boolean;
    /// Optionally specify the (super)set of `.rs`
    /// files comprising this crate.
    ///
    /// By default, rust-analyzer assumes that only
    /// files under `root_module.parent` can belong
    /// to a crate. `include_dirs` are included
    /// recursively, unless a subdirectory is in
    /// `exclude_dirs`.
    ///
    /// Different crates can share the same `source`.
    ///
    /// If two crates share an `.rs` file in common,
    /// they *must* have the same `source`.
    /// rust-analyzer assumes that files from one
    /// source can't refer to files in another source.
    source?: {
        include_dirs: string[],
        exclude_dirs: string[],
    },
    /// The set of cfgs activated for a given crate, like
    /// `["unix", "feature=\"foo\"", "feature=\"bar\""]`.
    cfg: string[];
    /// Target triple for this Crate.
    ///
    /// Used when running `rustc --print cfg`
    /// to get target-specific cfgs.
    target?: string;
    /// Environment variables, used for
    /// the `env!` macro
    env: { [key: string]: string; },

    /// Whether the crate is a proc-macro crate.
    is_proc_macro: boolean;
    /// For proc-macro crates, path to compiled
    /// proc-macro (.so file).
    proc_macro_dylib_path?: string;
}

interface Dep {
    /// Index of a crate in the `crates` array.
    crate: number,
    /// Name as should appear in the (implicit)
    /// `extern crate name` declaration.
    name: string,
}

This format is provisional and subject to change. Specifically, the roots setup will be different eventually.

There are three ways to feed rust-project.json to rust-analyzer:

  • Place rust-project.json file at the root of the project, and rust-analyzer will discover it.

  • Specify "rust-analyzer.linkedProjects": [ "path/to/rust-project.json" ] in the settings (and make sure that your LSP client sends settings as a part of initialize request).

  • Specify "rust-analyzer.linkedProjects": [ { "roots": […​], "crates": […​] }] inline.

Relative paths are interpreted relative to rust-project.json file location or (for inline JSON) relative to rootUri.

You can set the RA_LOG environment variable to rust_analyzer=info to inspect how rust-analyzer handles config and project loading.

Note that calls to cargo check are disabled when using rust-project.json by default, so compilation errors and warnings will no longer be sent to your LSP client. To enable these compilation errors you will need to specify explicitly what command rust-analyzer should run to perform the checks using the rust-analyzer.check.overrideCommand configuration. As an example, the following configuration explicitly sets cargo check as the check command.

{ "rust-analyzer.check.overrideCommand": ["cargo", "check", "--message-format=json"] }

check.overrideCommand requires the command specified to output json error messages for rust-analyzer to consume. The --message-format=json flag does this for cargo check so whichever command you use must also output errors in this format. See the Configuration section for more information.

Security

At the moment, rust-analyzer assumes that all code is trusted. Here is a non-exhaustive list of ways to make rust-analyzer execute arbitrary code:

  • proc macros and build scripts are executed by default

  • .cargo/config can override rustc with an arbitrary executable

  • rust-toolchain.toml can override rustc with an arbitrary executable

  • VS Code plugin reads configuration from project directory, and that can be used to override paths to various executables, like rustfmt or rust-analyzer itself.

  • rust-analyzer’s syntax trees library uses a lot of unsafe and hasn’t been properly audited for memory safety.

Privacy

The LSP server performs no network access in itself, but runs cargo metadata which will update or download the crate registry and the source code of the project dependencies. If enabled (the default), build scripts and procedural macros can do anything.

The Code extension does not access the network.

Any other editor plugins are not under the control of the rust-analyzer developers. For any privacy concerns, you should check with their respective developers.

For rust-analyzer developers, cargo xtask release uses the GitHub API to put together the release notes.

Assists (Code Actions)

Assists, or code actions, are small local refactorings, available in a particular context. They are usually triggered by a shortcut or by clicking a light bulb icon in the editor. Cursor position or selection is signified by ┃ character.

Diagnostics

While most errors and warnings provided by rust-analyzer come from the cargo check integration, there’s a growing number of diagnostics implemented using rust-analyzer’s own analysis. Some of these diagnostics don’t respect #[allow] or \#[deny] attributes yet, but can be turned off using the rust-analyzer.diagnostics.enable, rust-analyzer.diagnostics.experimental.enable or rust-analyzer.diagnostics.disabled settings.

Clippy

To run cargo clippy instead of cargo check, you can set "rust-analyzer.check.command": "clippy".

Editor Features

VS Code

Color configurations

It is possible to change the foreground/background color and font family/size of inlay hints. Just add this to your settings.json:

{
  "editor.inlayHints.fontFamily": "Courier New",
  "editor.inlayHints.fontSize": 11,

  "workbench.colorCustomizations": {
    // Name of the theme you are currently using
    "[Default Dark+]": {
      "editorInlayHint.foreground": "#868686f0",
      "editorInlayHint.background": "#3d3d3d48",

      // Overrides for specific kinds of inlay hints
      "editorInlayHint.typeForeground": "#fdb6fdf0",
      "editorInlayHint.parameterForeground": "#fdb6fdf0",
    }
  }
}

Semantic style customizations

You can customize the look of different semantic elements in the source code. For example, mutable bindings are underlined by default and you can override this behavior by adding the following section to your settings.json:

{
  "editor.semanticTokenColorCustomizations": {
    "rules": {
      "*.mutable": {
        "fontStyle": "", // underline is the default
      },
    }
  },
}

Most themes doesn’t support styling unsafe operations differently yet. You can fix this by adding overrides for the rules operator.unsafe, function.unsafe, and method.unsafe:

{
   "editor.semanticTokenColorCustomizations": {
         "rules": {
             "operator.unsafe": "#ff6600",
             "function.unsafe": "#ff6600",
             "method.unsafe": "#ff6600"
         }
    },
}

In addition to the top-level rules you can specify overrides for specific themes. For example, if you wanted to use a darker text color on a specific light theme, you might write:

{
   "editor.semanticTokenColorCustomizations": {
         "rules": {
             "operator.unsafe": "#ff6600"
         },
         "[Ayu Light]": {
            "rules": {
               "operator.unsafe": "#572300"
            }
         }
    },
}

Make sure you include the brackets around the theme name. For example, use "[Ayu Light]" to customize the theme Ayu Light.

Special when clause context for keybindings.

You may use inRustProject context to configure keybindings for rust projects only. For example:

{
  "key": "ctrl+alt+d",
  "command": "rust-analyzer.openDocs",
  "when": "inRustProject"
}

More about when clause contexts here.

Setting runnable environment variables

You can use "rust-analyzer.runnables.extraEnv" setting to define runnable environment-specific substitution variables. The simplest way for all runnables in a bunch:

"rust-analyzer.runnables.extraEnv": {
    "RUN_SLOW_TESTS": "1"
}

Or it is possible to specify vars more granularly:

"rust-analyzer.runnables.extraEnv": [
    {
        // "mask": null, // null mask means that this rule will be applied for all runnables
        "env": {
             "APP_ID": "1",
             "APP_DATA": "asdf"
        }
    },
    {
        "mask": "test_name",
        "env": {
             "APP_ID": "2", // overwrites only APP_ID
        }
    }
]

You can use any valid regular expression as a mask. Also note that a full runnable name is something like run bin_or_example_name, test some::mod::test_name or test-mod some::mod, so it is possible to distinguish binaries, single tests, and test modules with this masks: "^run", "^test " (the trailing space matters!), and "^test-mod" respectively.

If needed, you can set different values for different platforms:

"rust-analyzer.runnables.extraEnv": [
    {
        "platform": "win32", // windows only
        "env": {
             "APP_DATA": "windows specific data"
        }
    },
    {
        "platform": ["linux"],
        "env": {
             "APP_DATA": "linux data",
        }
    },
    { // for all platforms
        "env": {
             "APP_COMMON_DATA": "xxx",
        }
    }
]

Compiler feedback from external commands

Instead of relying on the built-in cargo check, you can configure Code to run a command in the background and use the $rustc-watch problem matcher to generate inline error markers from its output.

To do this you need to create a new VS Code Task and set "rust-analyzer.checkOnSave": false in preferences.

For example, if you want to run cargo watch instead, you might add the following to .vscode/tasks.json:

{
    "label": "Watch",
    "group": "build",
    "type": "shell",
    "command": "cargo watch",
    "problemMatcher": "$rustc-watch",
    "isBackground": true
}

Live Share

VS Code Live Share has partial support for rust-analyzer.

Live Share requires the official Microsoft build of VS Code, OSS builds will not work correctly.

The host’s rust-analyzer instance will be shared with all guests joining the session. The guests do not have to have the rust-analyzer extension installed for this to work.

If you are joining a Live Share session and do have rust-analyzer installed locally, commands from the command palette will not work correctly since they will attempt to communicate with the local server.