c7dd3c4d69
This PR removes boxed closures from the language, the closure type syntax (`let f: |int| -> bool = /* ... */`) has been obsoleted. Move all your uses of closures to the new unboxed closure system (i.e. `Fn*` traits).
[breaking-change] patterns
- `lef f = || {}`
This binding used to type check to a boxed closure. Now that boxed closures are gone, you need to annotate the "kind" of the unboxed closure, i.e. you need pick one of these: `|&:| {}`, `|&mut:| {}` or `|:| {}`.
In the (near) future we'll have closure "kind" inference, so the compiler will infer which `Fn*` trait to use based on how the closure is used. Once this inference machinery is in place, we'll be able to remove the kind annotation from most closures.
- `type Alias<'a> = |int|:'a -> bool`
Use a trait object: `type Alias<'a> = Box<FnMut(int) -> bool + 'a>`. Use the `Fn*` trait that makes sense for your use case.
- `fn foo(&self, f: |uint| -> bool)`
In this case you can use either a trait object or an unboxed closure:
``` rust
fn foo(&self, f: F) where F: FnMut(uint) -> bool;
// or
fn foo(&self, f: Box<FnMut(uint) -> bool>);
```
- `struct Struct<'a> { f: |uint|:'a -> bool }`
Again, you can use either a trait object or an unboxed closure:
``` rust
struct Struct<F> where F: FnMut(uint) -> bool { f: F }
// or
struct Struct<'a> { f: Box<FnMut(uint) -> bool + 'a> }
```
- Using `|x, y| f(x, y)` for closure "borrows"
This comes up in recursive functions, consider the following (contrived) example:
``` rust
fn foo(x: uint, f: |uint| -> bool) -> bool {
//foo(x / 2, f) && f(x) // can't use this because `f` gets moved away in the `foo` call
foo(x / 2, |x| f(x)) && f(x) // instead "borrow" `f` in the `foo` call
}
```
If you attempt to do the same with unboxed closures you'll hit ""error: reached the recursion limit during monomorphization" (see #19596):
``` rust
fn foo<F>(x: uint, mut f: F) -> bool where F: FnMut(uint) -> bool {
foo(x / 2, |x| f(x)) && f(x)
//~^ error: reached the recursion limit during monomorphization
}
```
Instead you *should* be able to write this:
``` rust
fn foo<F>(x: uint, mut f: F) -> bool where F: FnMut(uint) -> bool {
foo(x / 2, &mut f) && f(x)
//~^ error: the trait `FnMut` is not implemented for the type `&mut F`
}
```
But as you see above `&mut F` doesn't implement the `FnMut` trait. `&mut F` *should* implement the `FnMut` and the above code *should* work, but due to a bug (see #18835) it doesn't (for now).
You can work around the issue by rewriting the function to take `&mut F` instead of `F`:
``` rust
fn foo<F>(x: uint, f: &mut F) -> bool where F: FnMut(uint) -> bool {
foo(x / 2, f) && (*f)(x)
}
```
This finally works! However writing `foo(0, &mut |x| x == 0)` is unergonomic. So you can use a private helper function to avoid this:
``` rust
// public API function
pub fn foo<F>(x: uint, mut f: F) -> bool where F: FnMut(uint) -> bool {
foo_(x, &mut f)
}
// private helper function
fn foo_<F>(x: uint, f: &mut F) -> bool where F: FnMut(uint) -> bool {
foo_(x / 2, f) && (*f)(x)
}
```
Closes #14798
---
There is more cleanup to do: like renaming functions/types from `unboxed_closure` to just `closure`, removing more dead code, simplify functions which now have unused arguments, update the documentation, etc. But that can be done in another PR.
r? @nikomatsakis @aturon (You probably want to focus on the deleted/modified tests.)
cc @eddyb
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| src | ||
| .gitattributes | ||
| .gitignore | ||
| .gitmodules | ||
| .mailmap | ||
| .travis.yml | ||
| AUTHORS.txt | ||
| configure | ||
| CONTRIBUTING.md | ||
| COPYRIGHT | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| Makefile.in | ||
| README.md | ||
| RELEASES.md | ||
The Rust Programming Language
This is a compiler for Rust, including standard libraries, tools and documentation.
Quick Start
- Download a binary installer for your platform.
- Read the guide.
- Enjoy!
Note: Windows users can read the detailed using Rust on Windows notes on the wiki.
Building from Source
-
Make sure you have installed the dependencies:
g++4.7 orclang++3.xpython2.6 or later (but not 3.x)perl5.0 or later- GNU
make3.81 or later curlgit
-
Download and build Rust:
You can either download a tarball or build directly from the repo.
To build from the tarball do:
$ curl -O https://static.rust-lang.org/dist/rust-nightly.tar.gz $ tar -xzf rust-nightly.tar.gz $ cd rust-nightlyOr to build from the repo do:
$ git clone https://github.com/rust-lang/rust.git $ cd rustNow that you have Rust's source code, you can configure and build it:
$ ./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. -
Read the guide.
-
Enjoy!
Building on Windows
To easily build on windows we can use MSYS2:
-
Grab the latest MSYS2 installer and go through the installer.
-
Now from the MSYS2 terminal we want to install the mingw64 toolchain and the other tools we need.
$ pacman -S mingw-w64-i686-toolchain $ pacman -S base-devel -
With that now start
mingw32_shell.batfrom where you installed MSYS2 (i.e.C:\msys). -
From there just navigate to where you have 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 a lot more documentation in the wiki.
Getting help and getting involved
The Rust community congregates in a few places:
- StackOverflow - Get help here.
- /r/rust - General discussion.
- discuss.rust-lang.org - For development of the Rust language itself.
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.