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Felix S. Klock II ee06263f92 Fallout from fixing Issue 25199. 
There are two interesting kinds of breakage illustrated here:

1. `Box<Trait>` in many contexts is treated as `Box<Trait + 'static>`,
   due to [RFC 599]. However, in a type like `&'a Box<Trait>`, the
   `Box<Trait>` type will be expanded to `Box<Trait + 'a>`, again due
   to [RFC 599]. This, combined with the fix to Issue 25199, leads to
   a borrowck problem due the combination of this function signature
   (in src/libstd/net/parser.rs):

   ```rust
   fn read_or<T>(&mut self, parsers: &mut [Box<FnMut(&mut Parser) -> Option<T>>]) -> Option<T>;
   ```

   with this call site (again in src/libstd/net/parser.rs):

   ```rust
   fn read_ip_addr(&mut self) -> Option<IpAddr> {
       let ipv4_addr = |p: &mut Parser| p.read_ipv4_addr().map(|v4| IpAddr::V4(v4));
       let ipv6_addr = |p: &mut Parser| p.read_ipv6_addr().map(|v6| IpAddr::V6(v6));
       self.read_or(&mut [Box::new(ipv4_addr), Box::new(ipv6_addr)])
   }
   ```

   yielding borrowck errors like:

   ```
   parser.rs:265:27: 265:69 error: borrowed value does not live long enough
   parser.rs:265         self.read_or(&mut [Box::new(ipv4_addr), Box::new(ipv6_addr)])
                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   ```

   (full log at: https://gist.github.com/pnkfelix/e2e80f1a71580f5d3103 )

   The issue here is perhaps subtle: the `parsers` argument is
   inferred to be taking a slice of boxed objects with the implicit
   lifetime bound attached to the `self` parameter to `read_or`.

   Meanwhile, the fix to Issue 25199 (added in a forth-coming commit)
   is forcing us to assume that each boxed object may have a
   destructor that could refer to state of that lifetime, and
   *therefore* that inferred lifetime is required to outlive the boxed
   object itself.

   In this case, the relevant boxed object here is not going to make
   any such references; I believe it is just an artifact of how the
   expression was built that it is not assigned type:

     `Box<FnMut(&mut Parser) -> Option<T> + 'static>`.

   (i.e., mucking with the expression is probably one way to fix this
   problem).

   But the other way to fix it, adopted here, is to change the
   `read_or` method type to force make the (presumably-intended)
   `'static` bound explicit on the boxed `FnMut` object.

   (Note: this is still just the *first* example of breakage.)

2. In `macro_rules.rs`, the `TTMacroExpander` trait defines a method
   with signature:

   ```rust
   fn expand<'cx>(&self, cx: &'cx mut ExtCtxt, ...) -> Box<MacResult+'cx>;
   ```

   taking a `&'cx mut ExtCtxt` as an argument and returning a
   `Box<MacResult'cx>`.

   The fix to Issue 25199 (added in aforementioned forth-coming
   commit) assumes that a value of type `Box<MacResult+'cx>` may, in
   its destructor, refer to a reference of lifetime `'cx`; thus the
   `'cx` lifetime is forced to outlive the returned value.

   Meanwhile, within `expand.rs`, the old code was doing:

   ```rust
   match expander.expand(fld.cx, ...).make_pat() { ... => immutable borrow of fld.cx ... }
   ```

   The problem is that the `'cx` lifetime, inferred for the
   `expander.expand` call, has now been extended so that it has to
   outlive the temporary R-value returned by `expanded.expand`.  But
   call is also reborrowing `fld.cx` *mutably*, which means that this
   reborrow must end before any immutable borrow of `fld.cx`; but
   there is one of those within the match body. (Note that the
   temporary R-values for the input expression to `match` all live as
   long as the whole `match` expression itself (see Issue #3511 and PR
   #11585).

   To address this, I moved the construction of the pat value into its
   own `let`-statement, so that the `Box<MacResult>` will only live
   for as long as the initializing expression for the `let`-statement,
   and thus allow the subsequent immutable borrow within the `match`.

[RFC 599]: https://github.com/rust-lang/rfcs/blob/master/text/0599-default-object-bound.md
2015-05-08 14:48:26 +02:00
man
mk Error index style tweaks. 2015-05-05 11:17:00 +10:00
src Fallout from fixing Issue 25199. 2015-05-08 14:48:26 +02:00
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README.md

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

  1. Make sure you have installed the dependencies:

    • g++ 4.7 or clang++ 3.x
    • python 2.6 or later (but not 3.x)
    • GNU make 3.81 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 && make install

    Note: You may need to use sudo make install if you do not normally have permission to modify the destination directory. The 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, 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

MSYS2 can be used to easily build Rust on Windows:

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

  2. From the MSYS2 terminal, install the mingw64 toolchain 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

  3. Run mingw32_shell.bat or mingw64_shell.bat from wherever you installed MYSY2 (i.e. C:\msys), depending on whether you want 32-bit or 64-bit Rust.

  4. 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:

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.