---

yaml
---
r: 169905
b: refs/heads/auto
c: a56e7ae
h: refs/heads/master
i:
  169903: 2ea8d5f
v: v3

Author: steveklabnik

[refs]

@@ -10,7 +10,7 @@ refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503
 refs/tags/release-0.3.1: 495bae036dfe5ec6ceafd3312b4dca48741e845b
 refs/tags/release-0.4: e828ea2080499553b97dfe33b3f4d472b4562ad7
 refs/tags/release-0.5: 7e3bcfbf21278251ee936ad53e92e9b719702d73
-refs/heads/auto: d46b8f1fce6da33df8bf7c8c74c2da7bc023f993
+refs/heads/auto: a56e7aee81733485d6edd415ab383347232e3c36
 refs/heads/servo: af82457af293e2a842ba6b7759b70288da276167
 refs/tags/release-0.6: b4ebcfa1812664df5e142f0134a5faea3918544c
 refs/tags/0.1: b19db808c2793fe2976759b85a355c3ad8c8b336

branches/auto/src/compiletest/compiletest.rs

@@ -339,9 +339,8 @@ pub fn is_test(config: &Config, testfile: &Path) -> bool {
     return valid;
 }
 
-pub fn make_test<F>(config: &Config, testfile: &Path, f: F) -> test::TestDescAndFn where
-    F: FnOnce() -> test::TestFn,
-{
+pub fn make_test(config: &Config, testfile: &Path, f: || -> test::TestFn)
+                 -> test::TestDescAndFn {
     test::TestDescAndFn {
         desc: test::TestDesc {
             name: make_test_name(config, testfile),

branches/auto/src/compiletest/header.rs

@@ -220,9 +220,7 @@ pub fn is_test_ignored(config: &Config, testfile: &Path) -> bool {
     !val
 }
 
-fn iter_header<F>(testfile: &Path, mut it: F) -> bool where
-    F: FnMut(&str) -> bool,
-{
+fn iter_header(testfile: &Path, it: |&str| -> bool) -> bool {
     use std::io::{BufferedReader, File};
 
     let mut rdr = BufferedReader::new(File::open(testfile).unwrap());

branches/auto/src/compiletest/runtest.rs

@@ -1233,14 +1233,12 @@ enum TargetLocation {
     ThisDirectory(Path),
 }
 
-fn make_compile_args<F>(config: &Config,
-                        props: &TestProps,
-                        extras: Vec<String> ,
-                        xform: F,
-                        testfile: &Path)
-                        -> ProcArgs where
-    F: FnOnce(&Config, &Path) -> TargetLocation,
-{
+fn make_compile_args(config: &Config,
+                     props: &TestProps,
+                     extras: Vec<String> ,
+                     xform: |&Config, &Path| -> TargetLocation,
+                     testfile: &Path)
+                     -> ProcArgs {
     let xform_file = xform(config, testfile);
     let target = if props.force_host {
         config.host.as_slice()

branches/auto/src/doc/guide-ownership.md

@@ -230,8 +230,9 @@ fn add_one(num: &int) -> int {
 ```
 
 Rust has a feature called 'lifetime elision,' which allows you to not write
-lifetime annotations in certain circumstances. This is one of them. Without
-eliding the lifetimes, `add_one` looks like this:
+lifetime annotations in certain circumstances. This is one of them. We will
+cover the others later. Without eliding the lifetimes, `add_one` looks like
+this:
 
 ```rust
 fn add_one<'a>(num: &'a int) -> int {
@@ -449,6 +450,80 @@ This is the simplest kind of multiple ownership possible. For example, there's
 also `Arc<T>`, which uses more expensive atomic instructions to be the
 thread-safe counterpart of `Rc<T>`.
 
+## Lifetime Elision
+
+Earlier, we mentioned 'lifetime elision,' a feature of Rust which allows you to
+not write lifetime annotations in certain circumstances. All references have a
+lifetime, and so if you elide a lifetime (like `&T` instead of `&'a T`), Rust
+will do three things to determine what those lifetimes should be.
+
+When talking about lifetime elision, we use the term 'input lifetime' and
+'output lifetime'. An 'input liftime' is a lifetime associated with a parameter
+of a function, and an 'output lifetime' is a lifetime associated with the return
+value of a function. For example, this function has an input lifetime:
+
+```{rust,ignore}
+fn foo<'a>(bar: &'a str)
+```
+
+This one has an output lifetime:
+
+```{rust,ignore}
+fn foo<'a>() -> &'a str
+```
+
+This one has a lifetime in both positions:
+
+```{rust,ignore}
+fn foo<'a>(bar: &'a str) -> &'a str
+```
+
+Here are the three rules:
+
+* Each elided lifetime in a function's arguments becomes a distinct lifetime
+  parameter.
+
+* If there is exactly one input lifetime, elided or not, that lifetime is
+  assigned to all elided lifetimes in the return values of that function..
+
+* If there are multiple input lifetimes, but one of them is `&self` or `&mut
+  self`, the lifetime of `self` is assigned to all elided output lifetimes.
+
+Otherwise, it is an error to elide an output lifetime.
+
+### Examples
+
+Here are some examples of functions with elided lifetimes, and the version of
+what the elided lifetimes are expand to:
+
+```{rust,ignore}
+fn print(s: &str);                                      // elided
+fn print<'a>(s: &'a str);                               // expanded
+
+fn debug(lvl: uint, s: &str);                           // elided
+fn debug<'a>(lvl: uint, s: &'a str);                    // expanded
+
+// In the preceeding example, `lvl` doesn't need a lifetime because it's not a
+// reference (`&`). Only things relating to references (such as a `struct`
+// which contains a reference) need lifetimes.
+
+fn substr(s: &str, until: uint) -> &str;                // elided
+fn substr<'a>(s: &'a str, until: uint) -> &'a str;      // expanded
+
+fn get_str() -> &str;                                   // ILLEGAL, no inputs
+
+fn frob(s: &str, t: &str) -> &str;                      // ILLEGAL, two inputs
+
+fn get_mut(&mut self) -> &mut T;                        // elided
+fn get_mut<'a>(&'a mut self) -> &'a mut T;              // expanded
+
+fn args<T:ToCStr>(&mut self, args: &[T]) -> &mut Command                  // elided
+fn args<'a, 'b, T:ToCStr>(&'a mut self, args: &'b [T]) -> &'a mut Command // expanded
+
+fn new(buf: &mut [u8]) -> BufWriter;                    // elided
+fn new<'a>(buf: &'a mut [u8]) -> BufWriter<'a>          // expanded
+```
+
 # Related Resources
 
 Coming Soon.

branches/auto/src/doc/guide-testing.md

@@ -537,8 +537,7 @@ computation entirely. This could be done for the example above by adjusting the
 `b.iter` call to
 
 ```rust
-# struct X;
-# impl X { fn iter<T, F>(&self, _: F) where F: FnMut() -> T {} } let b = X;
+# struct X; impl X { fn iter<T>(&self, _: || -> T) {} } let b = X;
 b.iter(|| {
     // note lack of `;` (could also use an explicit `return`).
     range(0u, 1000).fold(0, |old, new| old ^ new)
@@ -553,8 +552,7 @@ argument as used.
 extern crate test;
 
 # fn main() {
-# struct X;
-# impl X { fn iter<T, F>(&self, _: F) where F: FnMut() -> T {} } let b = X;
+# struct X; impl X { fn iter<T>(&self, _: || -> T) {} } let b = X;
 b.iter(|| {
     test::black_box(range(0u, 1000).fold(0, |old, new| old ^ new));
 });

branches/auto/src/doc/guide.md

@@ -4232,7 +4232,7 @@ arguments, really powerful things are possible.
 Let's make a closure:
 
 ```{rust}
-let add_one = |&: x| { 1 + x };
+let add_one = |x| { 1 + x };
 
 println!("The sum of 5 plus 1 is {}.", add_one(5));
 ```
@@ -4244,8 +4244,8 @@ binding name and two parentheses, just like we would for a named function.
 Let's compare syntax. The two are pretty close:
 
 ```{rust}
-let add_one = |&: x: i32| -> i32 { 1 + x };
-fn  add_one      (x: i32) -> i32 { 1 + x }
+let add_one = |x: i32| -> i32 { 1 + x };
+fn  add_one   (x: i32) -> i32 { 1 + x }
 ```
 
 As you may have noticed, closures infer their argument and return types, so you
@@ -4258,9 +4258,9 @@ this:
 
 ```{rust}
 fn main() {
-    let x: i32 = 5;
+    let x = 5;
 
-    let printer = |&:| { println!("x is: {}", x); };
+    let printer = || { println!("x is: {}", x); };
 
     printer(); // prints "x is: 5"
 }
@@ -4276,7 +4276,7 @@ defined. The closure borrows any variables it uses, so this will error:
 fn main() {
     let mut x = 5;
 
-    let printer = |&:| { println!("x is: {}", x); };
+    let printer = || { println!("x is: {}", x); };
 
     x = 6; // error: cannot assign to `x` because it is borrowed
 }
@@ -4298,12 +4298,12 @@ now. We'll talk about them more in the "Threads" section of the guide.
 Closures are most useful as an argument to another function. Here's an example:
 
 ```{rust}
-fn twice<F: Fn(i32) -> i32>(x: i32, f: F) -> i32 {
+fn twice(x: i32, f: |i32| -> i32) -> i32 {
     f(x) + f(x)
 }
 
 fn main() {
-    let square = |&: x: i32| { x * x };
+    let square = |x: i32| { x * x };
 
     twice(5, square); // evaluates to 50
 }
@@ -4312,15 +4312,15 @@ fn main() {
 Let's break the example down, starting with `main`:
 
 ```{rust}
-let square = |&: x: i32| { x * x };
+let square = |x: i32| { x * x };
 ```
 
 We've seen this before. We make a closure that takes an integer, and returns
 its square.
 
 ```{rust}
-# fn twice<F: Fn(i32) -> i32>(x: i32, f: F) -> i32 { f(x) + f(x) }
-# let square = |&: x: i32| { x * x };
+# fn twice(x: i32, f: |i32| -> i32) -> i32 { f(x) + f(x) }
+# let square = |x: i32| { x * x };
 twice(5, square); // evaluates to 50
 ```
 
@@ -4343,8 +4343,8 @@ how the `|i32| -> i32` syntax looks a lot like our definition of `square`
 above, if we added the return type in:
 
 ```{rust}
-let square = |&: x: i32| -> i32 { x * x };
-//           |i32|       -> i32
+let square = |x: i32| -> i32 { x * x };
+//           |i32|    -> i32
 ```
 
 This function takes an `i32` and returns an `i32`.
@@ -4358,7 +4358,7 @@ Finally, `twice` returns an `i32` as well.
 Okay, let's look at the body of `twice`:
 
 ```{rust}
-fn twice<F: Fn(i32) -> i32>(x: i32, f: F) -> i32 {
+fn twice(x: i32, f: |i32| -> i32) -> i32 {
   f(x) + f(x)
 }
 ```
@@ -4376,7 +4376,7 @@ If we didn't want to give `square` a name, we could just define it inline.
 This example is the same as the previous one:
 
 ```{rust}
-fn twice<F: Fn(i32) -> i32>(x: i32, f: F) -> i32 {
+fn twice(x: i32, f: |i32| -> i32) -> i32 {
     f(x) + f(x)
 }
 
@@ -4389,7 +4389,7 @@ A named function's name can be used wherever you'd use a closure. Another
 way of writing the previous example:
 
 ```{rust}
-fn twice<F: Fn(i32) -> i32>(x: i32, f: F) -> i32 {
+fn twice(x: i32, f: |i32| -> i32) -> i32 {
     f(x) + f(x)
 }