Auto merge of #112006 - kylematsuda:earlybinder-private, r=jackh726

Make `EarlyBinder`'s inner value private

Currently, `EarlyBinder(T)`'s inner value is public, which allows implicitly skipping the binder by indexing into the tuple struct (i.e., `x.0`). `@lcnr` suggested making `EarlyBinder`'s inner value private so users are required to explicitly call `skip_binder` ( .

This PR makes the inner value private, adds `EarlyBinder::new` for constructing a new instance, and replaces uses of `x.0` with `x.skip_binder()` (or similar). It also adds some documentation to `EarlyBinder::skip_binder` explaining how to skip the binder of `&EarlyBinder<T>` to get `&T` now that the inner value is private (since previously we could just do `&x.0`).

r? `@lcnr`
tree: cb51d4703b9467f6794bdee1a94df3909c2017b1
  1. .github/
  2. .reuse/
  3. compiler/
  4. library/
  6. src/
  7. tests/
  8. .editorconfig
  9. .git-blame-ignore-revs
  10. .gitattributes
  11. .gitignore
  12. .gitmodules
  13. .mailmap
  14. Cargo.lock
  15. Cargo.toml
  17. config.example.toml
  18. configure
  25. rustfmt.toml
  26. triagebot.toml
  27. x
  28. x.ps1

The Rust Programming Language

Rust Community

This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.

Note: this README is for users rather than contributors. If you wish to contribute to the compiler, you should read instead.

Quick Start

Read “Installation” from The Book.

Installing from Source

The Rust build system uses a Python script called to build the compiler, which manages the bootstrapping process. It lives at the root of the project. It also uses a file named config.toml to determine various configuration settings for the build. You can see a full list of options in config.example.toml.

The command can be run directly on most Unix systems in the following format:

./ <subcommand> [flags]

This is how the documentation and examples assume you are running Some alternative ways are:

# On a Unix shell if you don't have the necessary `python3` command
./x <subcommand> [flags]

# On the Windows Command Prompt (if .py files are configured to run Python) <subcommand> [flags]

# You can also run Python yourself, e.g.:
python <subcommand> [flags]

More information about can be found by running it with the --help flag or reading the rustc dev guide.


Make sure you have installed the dependencies:

  • python 3 or 2.7
  • git
  • A C compiler (when building for the host, cc is enough; cross-compiling may need additional compilers)
  • curl (not needed on Windows)
  • pkg-config if you are compiling on Linux and targeting Linux
  • libiconv (already included with glibc on Debian-based distros)

To build Cargo, you'll also need OpenSSL (libssl-dev or openssl-devel on most Unix distros).

If building LLVM from source, you'll need additional tools:

  • g++, clang++, or MSVC with versions listed on LLVM's documentation
  • ninja, or GNU make 3.81 or later (Ninja is recommended, especially on Windows)
  • cmake 3.13.4 or later
  • libstdc++-static may be required on some Linux distributions such as Fedora and Ubuntu

On tier 1 or tier 2 with host tools platforms, you can also choose to download LLVM by setting = true. Otherwise, you'll need LLVM installed and llvm-config in your path. See the rustc-dev-guide for more info.

Building on a Unix-like system

Build steps

  1. Clone the source with git:

    git clone
    cd rust
  1. Configure the build settings:


    If you plan to use install to create an installation, it is recommended that you set the prefix value in the [install] section to a directory: ./configure --set install.prefix=<path>

  2. Build and install:

    ./ build && ./ install

    When complete, ./ install will place several programs into $PREFIX/bin: rustc, the Rust compiler, and rustdoc, the API-documentation tool. By default, it will also include Cargo, Rust's package manager. You can disable this behavior by passing --set build.extended=false to ./configure.

Configure and Make

This project provides a configure script and makefile (the latter of which just invokes ./configure is the recommended way to programatically generate a config.toml. make is not recommended (we suggest using directly), but it is supported and we try not to break it unnecessarily.

make && sudo make install

configure generates a config.toml which can also be used with normal invocations.

Building on Windows

On Windows, we suggest using winget to install dependencies by running the following in a terminal:

winget install -e Python.Python.3
winget install -e Kitware.CMake
winget install -e Git.Git

Then edit your system's PATH variable and add: C:\Program Files\CMake\bin. See this guide on editing the system PATH from the Java documentation.

There are two prominent ABIs in use on Windows: the native (MSVC) ABI used by Visual Studio and the GNU ABI used by the GCC toolchain. Which version of Rust you need depends largely on what C/C++ libraries you want to interoperate with. Use the MSVC build of Rust to interop with software produced by Visual Studio and the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain.


MSYS2 can be used to easily build Rust on Windows:

  1. Download the latest MSYS2 installer and go through the installer.

  2. Run mingw32_shell.bat or mingw64_shell.bat from the MSYS2 installation directory (e.g. C:\msys64), depending on whether you want 32-bit or 64-bit Rust. (As of the latest version of MSYS2 you have to run msys2_shell.cmd -mingw32 or msys2_shell.cmd -mingw64 from the command line instead.)

  3. From this terminal, install the required tools:

    # Update package mirrors (may be needed if you have a fresh install of MSYS2)
    pacman -Sy pacman-mirrors
    # Install build tools needed for Rust. If you're building a 32-bit compiler,
    # then replace "x86_64" below with "i686". If you've already got Git, Python,
    # or CMake installed and in PATH you can remove them from this list.
    # Note that it is important that you do **not** use the 'python2', 'cmake',
    # and 'ninja' packages from the 'msys2' subsystem.
    # The build has historically been known to fail with these packages.
    pacman -S git \
                make \
                diffutils \
                tar \
                mingw-w64-x86_64-python \
                mingw-w64-x86_64-cmake \
                mingw-w64-x86_64-gcc \
  4. Navigate to Rust's source code (or clone it), then build it:

    python setup user && python build && python install


MSVC builds of Rust additionally require an installation of Visual Studio 2017 (or later) so rustc can use its linker. The simplest way is to get Visual Studio, check the “C++ build tools” and “Windows 10 SDK” workload.

(If you‘re installing CMake yourself, be careful that “C++ CMake tools for Windows” doesn’t get included under “Individual components”.)

With these dependencies installed, you can build the compiler in a cmd.exe shell with:

python setup user
python build

Right now, building Rust only works with some known versions of Visual Studio. If you have a more recent version installed and the build system doesn't understand, you may need to force rustbuild to use an older version. This can be done by manually calling the appropriate vcvars file before running the bootstrap.

CALL "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
python build

Specifying an ABI

Each specific ABI can also be used from either environment (for example, using the GNU ABI in PowerShell) by using an explicit build triple. The available Windows build triples are:

  • GNU ABI (using GCC)
    • i686-pc-windows-gnu
    • x86_64-pc-windows-gnu
  • The MSVC ABI
    • i686-pc-windows-msvc
    • x86_64-pc-windows-msvc

The build triple can be specified by either specifying --build=<triple> when invoking commands, or by creating a config.toml file (as described in Building on a Unix-like system), and passing --set<triple> to ./configure.

Building Documentation

If you‘d like to build the documentation, it’s almost the same:

./ doc

The generated documentation will appear under doc in the build directory for the ABI used. That is, if the ABI was x86_64-pc-windows-msvc, the directory will be build\x86_64-pc-windows-msvc\doc.


Since the Rust compiler is written in Rust, it must be built by a precompiled “snapshot” version of itself (made in an earlier stage of development). As such, source builds require an Internet connection to fetch snapshots, and an OS that can execute the available snapshot binaries.

See for a list of supported platforms. Only “host tools” platforms have a pre-compiled snapshot binary available; to compile for a platform without host tools you must cross-compile.

You may find that other platforms work, but these are our officially supported build environments that are most likely to work.

Getting Help

See for a list of chat platforms and forums.




Rust is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.



The Rust Foundation owns and protects the Rust and Cargo trademarks and logos (the “Rust Trademarks”).

If you want to use these names or brands, please read the media guide.

Third-party logos may be subject to third-party copyrights and trademarks. See Licenses for details.