This is a quickstart guide about getting the compiler running. For more information in the individual steps, see the other pages in this chapter.

First, clone the repository:

git clone https://github.com/rust-lang/rust.git
cd rust

When building the compiler, we don't use cargo directly, instead we use a wrapper called "x". It is invoked with ./x.

We need to create a configuration for the build. Use ./x setup to create a good default.

./x setup

Then, we can build the compiler. Use ./x build to build the compiler, standard library and a few tools. You can also ./x check to just check it. All these commands can take specific components/paths as arguments, for example ./x check compiler to just check the compiler.

./x build

When doing a change to the compiler that does not affect the way it compiles the standard library (so for example, a change to an error message), use --keep-stage-std 1 to avoid recompiling it.

After building the compiler and standard library, you now have a working compiler toolchain. You can use it with rustup by linking it.

rustup toolchain link stage1 build/host/stage1

Now you have a toolchain called stage1 linked to your build. You can use it to test the compiler.

rustc +stage1 testfile.rs

After doing a change, you can run the compiler test suite with ./x test.

./x test runs the full test suite, which is slow and rarely what you want. Usually, ./x test tests/ui is what you want after a compiler change, testing all UI tests that invoke the compiler on a specific test file and check the output.

./x test tests/ui

Use --bless if you've made a change and want to update the .stderr files with the new output.

./x suggest can also be helpful for suggesting which tests to run after a change.

Congrats, you are now ready to make a change to the compiler! If you have more questions, the full chapter might contain the answers, and if it doesn't, feel free to ask for help on Zulip.

If you use VSCode, ./x setup will ask you if you want to set up the config. For other editors, check out suggested workflows.