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contains ref-bindings, do not permit any upcasting from the type of the value being matched. Similarly, do not permit coercion in a `let`. This is a [breaking-change] in that it closes a type hole that previously existed, and in that coercion is not performed. You should be able to work around the latter by converting: ```rust let ref mut x: T = expr; ``` into ```rust let x: T = expr; let ref mut x = x; ``` Restricting coercion not to apply in the case of `let ref` or `let ref mut` is sort of unexciting to me, but seems the best solution: 1. Mixing coercion and `let ref` or `let ref mut` is a bit odd, because you are taking the address of a (coerced) temporary, but only sometimes. It's not syntactically evident, in other words, what's going on. When you're doing a coercion, you're kind of 2. Put another way, I would like to preserve the relationship that `equality <= subtyping <= coercion <= as-coercion`, where this is an indication of the number of `(T1,T2)` pairs that are accepted by the various relations. Trying to mix `let ref mut` and coercion would create another kind of relation that is like coercion, but acts differently in the case where a precise match is needed. 3. In any case, this is strictly more conservative than what we had before and we can undo it in the future if we find a way to make coercion mix with type equality. The change to match I feel ok about but similarly unthrilled. There is some subtle text already concerning whether to use eqtype or subtype for identifier bindings. The best fix I think would be to always have match use strict equality but use subtyping on identifier bindings, but the comment `(*)` explains why that's not working at the moment. As above, I think we can change this as we clean up the code there.
The Rust Programming Language
This is a compiler for Rust, including standard libraries, tools and documentation. Rust is a systems programming language that is fast, memory safe and multithreaded, but does not employ a garbage collector or otherwise impose significant runtime overhead.
Quick Start
Read "Installing Rust" from The Book.
Building from Source
-
Make sure you have installed the dependencies:
g++4.7 orclang++3.xpython2.6 or later (but not 3.x)- GNU
make3.81 or later curlgit
-
Clone the source with
git:$ git clone https://github.com/rust-lang/rust.git $ cd rust
-
Build and install:
$ ./configure $ make && make installNote: You may need to use
sudo make installif you do not normally have permission to modify the destination directory. The install locations can be adjusted by passing a--prefixargument toconfigure. Various other options are also supported – pass--helpfor more information on them.When complete,
make installwill place several programs into/usr/local/bin:rustc, the Rust compiler, andrustdoc, the API-documentation tool. This install does not include Cargo, Rust's package manager, which you may also want to build.
Building on Windows
MSYS2 can be used to easily build Rust on Windows:
-
Grab the latest MSYS2 installer and go through the installer.
-
From the MSYS2 terminal, install the
mingw64toolchain and other required tools.# Choose one based on platform: $ pacman -S mingw-w64-i686-toolchain $ pacman -S mingw-w64-x86_64-toolchain $ pacman -S base-devel -
Run
mingw32_shell.batormingw64_shell.batfrom wherever you installed MYSY2 (i.e.C:\msys), depending on whether you want 32-bit or 64-bit Rust. -
Navigate to Rust's source code, configure and build it:
$ ./configure $ make && make install
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:
- Windows (7, 8, Server 2008 R2), x86 and x86-64 (64-bit support added in Rust 0.12.0)
- Linux (2.6.18 or later, various distributions), x86 and x86-64
- OSX 10.7 (Lion) or greater, x86 and x86-64
You may find that other platforms work, but these are our officially supported build environments that are most likely to work.
Rust currently needs about 1.5 GiB of RAM to build without swapping; 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:
- Stack Overflow - Direct questions about using the language.
- users.rust-lang.org - General discussion and broader questions.
- /r/rust - News and general discussion.
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.
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.