I was looking for an Emacs mode that could help me to hack on rust.
Rust-mode itself has not enough features to help me with a language I am not really proficient with yet.
I wanted to give a try to racer, which is available in the emacs packages list.
The rust toolchain available on Fedora 29 seems not able to build racer, so the first step was to install rust from rustup.rs and pretended it is completely fine to pipe curl into sh.
Once rustup was installed, I then needed the nightly toolchain and the rust-src component so that racer is able to navigate into the Rust source code.
$ curl https://sh.rustup.rs -sSf | sh
$ cargo +nightly install racer
$ rustup component add rust-src
At this point I installed the racer-mode package from Emacs. To do so, M-xthen list-packages, in the new buffer find racer-mode, then press I to select it and X to install it. If you don’t find it in the list of the packages, you might need to configure the packages archive to use. This is what I am using from ~/.emacs:
(when (>= emacs-major-version 24)
(require 'package)
(add-to-list
'package-archives
'("melpa" . "http://melpa.org/packages/")
t)
(package-initialize))
Finally I had to configure in my ~/.emacs file the path for racer to look for source files:
(setq racer-rust-src-path "~/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/")
At this point everything is configured to start using racer-mode.
You can open a .rs file, and set the mode with M-x racer-mode (if you are happy with it, you can configure it for any file with the .rs extension).
For a quick try, using M-. on a stdlib function name should bring you to the definition of the function, M-, to go back to its usage.