src/doc/rustc-dev-guide/README.md

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This is a collaborative effort to build a guide that explains how rustc
works. The aim of the guide is to help new contributors get oriented
to rustc, as well as to help more experienced folks in figuring out
some new part of the compiler that they haven't worked on before.

[You can read the latest version of the guide here.](https://rustc-dev-guide.rust-lang.org/)

You may also find the rustdocs [for the compiler itself][rustdocs] useful.
Note that these are not intended as a guide; it's recommended that you search
for the docs you're looking for instead of reading them top to bottom.

[rustdocs]: https://doc.rust-lang.org/nightly/nightly-rustc

For documentation on developing the standard library, see
[`std-dev-guide`](https://std-dev-guide.rust-lang.org/).

### Contributing to the guide

The guide is useful today, but it has a lot of work still to go.

If you'd like to help improve the guide, we'd love to have you! You can find
plenty of issues on the [issue
tracker](https://github.com/rust-lang/rustc-dev-guide/issues). Just post a
comment on the issue you would like to work on to make sure that we don't
accidentally duplicate work. If you think something is missing, please open an
issue about it!

**In general, if you don't know how the compiler works, that is not a
problem!** In that case, what we will do is to schedule a bit of time
for you to talk with someone who **does** know the code, or who wants
to pair with you and figure it out.  Then you can work on writing up
what you learned.

In general, when writing about a particular part of the compiler's code, we
recommend that you link to the relevant parts of the [rustc
rustdocs][rustdocs].

### Build Instructions

To build a local static HTML site, install [`mdbook`](https://github.com/rust-lang/mdBook) with:

```
cargo install mdbook mdbook-linkcheck2 mdbook-toc mdbook-mermaid
```

and execute the following command in the root of the repository:

```
mdbook build --open
```

The build files are found in the `book/html` directory.

### Link Validations

We use `mdbook-linkcheck2` to validate URLs included in our documentation. Link
checking is **not** run by default locally, though it is in CI. To enable it
locally, set the environment variable `ENABLE_LINKCHECK=1` like in the
following example.

```
ENABLE_LINKCHECK=1 mdbook serve
```

### Table of Contents

We use `mdbook-toc` to auto-generate TOCs for long sections. You can invoke the preprocessor by
including the `<!-- toc -->` marker at the place where you want the TOC.

## Synchronizing josh subtree with rustc

This repository is linked to `rust-lang/rust` as a [josh](https://josh-project.github.io/josh/intro.html) subtree. You can use the [rustc-josh-sync](https://github.com/rust-lang/josh-sync) tool to perform synchronization.

You can find a guide on how to perform the synchronization [here](./src/external-repos.md#synchronizing-a-josh-subtree).