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Guillaume Gomez 630b9e10c4 Rollup merge of #39084 - sphela:book-update-patterns, r=steveklabnik
An update to patterns documentation

As it is written the current pattern page creates a lot of confusion, even for someone with previous rust experience. It's so hard because it introduces an entirely new language feature without explaining. Someone could update it within the span of a few minutes by just explaining the newly introduced feature.

```rust
match c {
    x => println!("x: {} c: {}", x, c),
}
```
No where in the book up to this point has it explained that identifiers match patterns with just a name create an irrefutable pattern. The page uses this feature without explanation, it just assumes that readers would immediately understand it. To confuse the issue even further the topic uses this feature to explain shadowing, placing two x's from different scopes and different meanings without ever explaining why there is shadowing.

What follows comes across as utterly nonsensical given everything the reader would know about Rust about this point:

```rust
the result:
x: c c: c
x: x
```

x is c? What? Yes even if you understand that x here is not the x in the previous scope why would x equal 'c' here? What previous chapter explained this? The previous chapter on 'matching' only mentions the catch all '_' and never in any shape or form mentioned that a name here creates an irrefutable pattern and binds a value.

There are numerous examples of people not understanding this section, not finding answers and looking for them online about `x: c c: c`:

https://github.com/rust-lang/book/issues/316

https://stackoverflow.com/questions/35563141/match-shadowing-example-in-the-patterns-section-of-the-rust-book-is-very-perplex

https://users.rust-lang.org/t/confusion-about-match-and-patterns/3937

https://www.bountysource.com/issues/38852461-question-on-patterns-section-shadowing-example-existing-book

And a [google search for `rust x: c c: c`](https://www.google.com/search?q=rust+%22x:+c+c:+c%22) finds many more people being tripped up, including people who speak a language other than English. I am confident that this page has resulted in questions on the irc channel more than once. Given rust already has a pretty big learning curve I recommend this be fixed.

I was asked to create PR from where I made this same case in the [rust book repository issue](https://github.com/rust-lang/book/issues/316) (I didn't realize this was a separate project).
2017-01-16 22:48:24 +01:00
man Update man pages 2016-08-31 15:54:34 +02:00
mk Avoid large number of stage 0 warnings about --no-stack-check 2017-01-08 15:12:03 +03:00
src Rollup merge of #39084 - sphela:book-update-patterns, r=steveklabnik 2017-01-16 22:48:24 +01:00
.gitattributes rustbuild: Tweak for vendored dependencies 2016-11-08 07:32:05 -08:00
.gitignore Reduce the size of static data in std_unicode::tables. 2017-01-03 08:28:58 +01:00
.gitmodules Update .gitmodules 2016-02-20 20:37:30 +09:00
.mailmap update mailmap 2017-01-13 14:24:48 -05:00
.travis.yml Auto merge of #39042 - alexcrichton:upload-more, r=brson 2017-01-15 23:49:24 +00:00
appveyor.yml travis: Start uploading artifacts on commits 2017-01-12 15:29:04 -08:00
COMPILER_TESTS.md Add docs 2017-01-12 23:53:02 +01:00
configure Detect mips CPUs in ./configure 2017-01-12 19:33:45 +01:00
CONTRIBUTING.md Document --test-args for rustbuild 2016-12-14 01:31:48 +09:00
COPYRIGHT Mention initial copyright year 2016-01-28 09:44:04 +05:30
LICENSE-APACHE
LICENSE-MIT Mention initial copyright year 2016-01-28 09:44:04 +05:30
Makefile.in Fixed the TAGS.rustc.emacs and TAGS.rustc.vi make targets. 2016-06-17 12:07:48 +02:00
README.md Clarify phrasing of MSYS2 dependencies in README.md. 2016-12-21 14:21:49 -08:00
RELEASES.md Edits. More platform support 2016-12-17 23:02:35 +00:00
x.py Handle Ctrl+C in the build script 2016-12-11 15:25:31 +00:00

The Rust Programming Language

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

Quick Start

Read "Installing Rust" from The Book.

Building from Source

  1. Make sure you have installed the dependencies:

    • g++ 4.7 or later or clang++ 3.x
    • python 2.7 (but not 3.x)
    • GNU make 3.81 or later
    • cmake 3.4.3 or later
    • curl
    • git
  2. Clone the source with git:

    $ git clone https://github.com/rust-lang/rust.git
    $ cd rust
    
  1. Build and install:

    $ ./configure
    $ make && sudo make install
    

    Note: Install locations can be adjusted by passing a --prefix argument to configure. Various other options are also supported pass --help for more information on them.

    When complete, sudo make install will place several programs into /usr/local/bin: rustc, the Rust compiler, and rustdoc, the API-documentation tool. This install does not include Cargo, Rust's package manager, which you may also want to build.

Building on Windows

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: for interop with software produced by Visual Studio use the MSVC build of Rust; for interop with GNU software built using the MinGW/MSYS2 toolchain use the GNU build.

MinGW

MSYS2 can be used to easily build Rust on Windows:

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

  2. Run mingw32_shell.bat or mingw64_shell.bat from wherever you installed MSYS2 (i.e. 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' and 'cmake'
    # 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-python2 \
                mingw-w64-x86_64-cmake \
                mingw-w64-x86_64-gcc
    
  4. Navigate to Rust's source code (or clone it), then configure and build it:

    $ ./configure
    $ make && make install
    

MSVC

MSVC builds of Rust additionally require an installation of Visual Studio 2013 (or later) so rustc can use its linker. Make sure to check the “C++ tools” option.

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

> python x.py build

If you're running inside of an msys shell, however, you can run:

$ ./configure --build=x86_64-pc-windows-msvc
$ make && make install

Currently building Rust only works with some known versions of Visual Studio. If you have a more recent version installed the build system doesn't understand then 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 14.0\VC\bin\amd64\vcvars64.bat"
python x.py build

Building Documentation

If youd like to build the documentation, its almost the same:

$ ./configure
$ make docs

The generated documentation will appear in a top-level doc directory, created by the make rule.

Notes

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

Snapshot binaries are currently built and tested on several platforms:

Platform / Architecture x86 x86_64
Windows (7, 8, Server 2008 R2)
Linux (2.6.18 or later)
OSX (10.7 Lion or later)

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

Rust currently needs between 600MiB and 1.5GiB to build, depending on platform. If it hits swap, it will take a very long time to build.

There is more advice about hacking on Rust in CONTRIBUTING.md.

Getting Help

The Rust community congregates in a few places:

Contributing

To contribute to Rust, please see CONTRIBUTING.

Rust has an IRC culture and most real-time collaboration happens in a variety of channels on Mozilla's IRC network, irc.mozilla.org. The most popular channel is #rust, a venue for general discussion about Rust. And a good place to ask for help would be #rust-beginners.

License

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.

See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details.