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Fancy Rust development with Emacs 2016-05-14 15:10:00

Rustup beta was released this week. As a member of the Church of Emacs I needed to update my config a bit. This inspired me to write this post on how to setup your Emacs as a great Rust IDE.

Installing Rust

Thanks to rustup installing Rust on your system is now even easier. First do:

λ curl https://sh.rustup.rs -sSf | sh

When prompted choose 1) Proceed with installation (default) unless you have some special requirements.

rustup was previously named multirust. It will create a ~/.multirust directory to store rust toolchains.

The binaries and tools will be installed in ~/.cargo. Make sure that you have ~/.cargo/bin in your PATH otherwise add it with:

export PATH="$HOME/.cargo/bin:$PATH"

By default your projects will use the stable toolchain (Rust 1.8 at the time of this writing).

rustup has a lot of functionalities which you can find more about on the github page.

Crates and packages you’ll need

For this part I assume you already have a working emacs and that you know how to install packages and organize your configuration.


rust-mode handles syntax highlighting, indentation and various settings for you.

Just M-x package-install rust-mode.


Cargo is Rust package manager. cargo.el is a minor mode which allows us to run cargo commands from emacs like:

and many others.

As for installation, nothing fancy just M-x package-install cargo and add:

(add-hook 'rust-mode-hook 'cargo-minor-mode)

Cargo run


rustfmt formats your code according to community style guidelines just like gofmt in the Go language world. It’s automatically handled by rust-mode.

First install the rustfmt crate:

λ cargo install rustfmt

I use C-c <tab> a lot in my emacs to automatically indent the current buffer so it would be nice if the same key combination would run rustfmt which also fixes indentation. So I simply added:

(add-hook 'rust-mode-hook
          (lambda ()
            (local-set-key (kbd "C-c <tab>") #'rust-format-buffer)))


The ìndent-buffer function I mentioned if you ever need it:

(defun indent-buffer ()
  "Indent current buffer according to major mode."
  (indent-region (point-min) (point-max)))


Racer is a code completion and source code navigation tool for Rust.

Install the racer crate:

λ cargo install racer

Rust source code is needed for auto-completion so clone it somewhere:

λ git clone git@github.com:rust-lang/rust.git

To use racer within emacs, do a M-x package-install racer and set it up like:

(setq racer-cmd "~/.cargo/bin/racer") ;; Rustup binaries PATH
(setq racer-rust-src-path "/Users/julien/Code/rust/src") ;; Rust source code PATH

(add-hook 'rust-mode-hook #'racer-mode)
(add-hook 'racer-mode-hook #'eldoc-mode)
(add-hook 'racer-mode-hook #'company-mode)

Note that racer relies on company-mode so install it if you haven’t.



flycheck is my prefered solution for on the fly syntax checking. It will compile your code in background and highlight the problematic parts.

Let’s M-x package-install flycheck-rust and then set it up like:

(add-hook 'flycheck-mode-hook #'flycheck-rust-setup)


Wrapping up

That’s all, you now have some great Rust support in your emacs with syntax highlighting, cargo handling, code formatting, errors highlighting, code-completion and source navigation. Happy Rust hacking!