Merge pull request #1 from rust-lang/master

Update fork

src/SUMMARY.md

@@ -69,7 +69,7 @@
         - [As output parameters](fn/closures/output_parameters.md)
         - [Examples in `std`](fn/closures/closure_examples.md)
             - [Iterator::any](fn/closures/closure_examples/iter_any.md)
-            - [Iterator::find](fn/closures/closure_examples/iter_find.md)
+            - [Searching through iterators](fn/closures/closure_examples/iter_find.md)
     - [Higher Order Functions](fn/hof.md)
     - [Diverging functions](fn/diverging.md)
 
@@ -139,8 +139,8 @@
     - [Iterators](trait/iter.md)
     - [`impl Trait`](trait/impl_trait.md)
     - [Clone](trait/clone.md)
-    - [Supertraits](traits/supertraits.md)
-    - [Disambiguating overlapping traits](traits/disambiguating.md)
+    - [Supertraits](trait/supertraits.md)
+    - [Disambiguating overlapping traits](trait/disambiguating.md)
 
 - [macro_rules!](macros.md)
     - [Syntax](macros/syntax.md)

src/conversion/string.md

@@ -38,7 +38,7 @@ trait is implemented for that type. This is implemented for numerous types
 within the standard library. To obtain this functionality on a user defined type
 simply implement the [`FromStr`] trait for that type.
 
-```rust
+```rust,editable
 fn main() {
     let parsed: i32 = "5".parse().unwrap();
     let turbo_parsed = "10".parse::<i32>().unwrap();

src/custom_types/enum.md

@@ -55,7 +55,7 @@ fn main() {
 
 ## Type aliases
 
-If you use a type alias, you can refer to each enum variant via its alias. 
+If you use a type alias, you can refer to each enum variant via its alias.
 This might be useful if the enum's name is too long or too generic, and you
 want to rename it.
 
@@ -93,16 +93,17 @@ impl VeryVerboseEnumOfThingsToDoWithNumbers {
 }
 ```
 
-To learn more about enums and type aliases, you can read the 
+To learn more about enums and type aliases, you can read the
 [stabilization report][aliasreport] from when this feature was stabilized into
-Rust. 
+Rust.
 
 ### See also:
 
-[`match`][match], [`fn`][fn], and [`String`][str], []
+[`match`][match], [`fn`][fn], and [`String`][str], ["Type alias enum variants" RFC][type_alias_rfc]
 
 [c_struct]: https://en.wikipedia.org/wiki/Struct_(C_programming_language)
 [match]: ../flow_control/match.md
 [fn]: ../fn.md
 [str]: ../std/str.md
 [aliasreport]: https://github.com/rust-lang/rust/pull/61682/#issuecomment-502472847
+[type_alias_rfc]: https://rust-lang.github.io/rfcs/2338-type-alias-enum-variants.html

src/flow_control/match.md

@@ -15,7 +15,7 @@ fn main() {
         // Match several values
         2 | 3 | 5 | 7 | 11 => println!("This is a prime"),
         // Match an inclusive range
-        13...19 => println!("A teen"),
+        13..=19 => println!("A teen"),
         // Handle the rest of cases
         _ => println!("Ain't special"),
     }
@@ -31,4 +31,4 @@ fn main() {
 
     println!("{} -> {}", boolean, binary);
 }
-```
+```

src/fn/closures/capture.md

@@ -18,37 +18,51 @@ fn main() {
     
     let color = "green";
 
-    // A closure to print `color` which immediately borrows (`&`)
-    // `color` and stores the borrow and closure in the `print`
-    // variable. It will remain borrowed until `print` goes out of
-    // scope. `println!` only requires `by reference` so it doesn't
+    // A closure to print `color` which immediately borrows (`&`) `color` and
+    // stores the borrow and closure in the `print` variable. It will remain
+    // borrowed until `print` is used the last time. 
+    //
+    // `println!` only requires arguments by immutable reference so it doesn't
     // impose anything more restrictive.
     let print = || println!("`color`: {}", color);
 
     // Call the closure using the borrow.
     print();
+
+    // `color` can be borrowed immutably again, because the closure only holds
+    // an immutable reference to `color`. 
+    let _reborrow = &color;
     print();
 
-    let mut count = 0;
+    // A move or reborrow is allowed after the final use of `print`
+    let _color_moved = color;
 
-    // A closure to increment `count` could take either `&mut count`
-    // or `count` but `&mut count` is less restrictive so it takes
-    // that. Immediately borrows `count`.
+
+    let mut count = 0;
+    // A closure to increment `count` could take either `&mut count` or `count`
+    // but `&mut count` is less restrictive so it takes that. Immediately
+    // borrows `count`.
     //
-    // A `mut` is required on `inc` because a `&mut` is stored inside.
-    // Thus, calling the closure mutates the closure which requires
-    // a `mut`.
+    // A `mut` is required on `inc` because a `&mut` is stored inside. Thus,
+    // calling the closure mutates the closure which requires a `mut`.
     let mut inc = || {
         count += 1;
         println!("`count`: {}", count);
     };
 
-    // Call the closure.
-    inc();
+    // Call the closure using a mutable borrow.
     inc();
 
-    //let _reborrow = &mut count;
+    // The closure still mutably borrows `count` because it is called later.
+    // An attempt to reborrow will lead to an error.
+    // let _reborrow = &count; 
     // ^ TODO: try uncommenting this line.
+    inc();
+
+    // The closure no longer needs to borrow `&mut count`. Therefore, it is
+    // possible to reborrow without an error
+    let _count_reborrowed = &mut count; 
+
     
     // A non-copy type.
     let movable = Box::new(3);
@@ -64,7 +78,7 @@ fn main() {
 
     // `consume` consumes the variable so this can only be called once.
     consume();
-    //consume();
+    // consume();
     // ^ TODO: Try uncommenting this line.
 }
 ```
@@ -82,7 +96,7 @@ fn main() {
     println!("{}", contains(&1));
     println!("{}", contains(&4));
 
-    // `println!("There're {} elements in vec", haystack.len());`
+    // println!("There're {} elements in vec", haystack.len());
     // ^ Uncommenting above line will result in compile-time error
     // because borrow checker doesn't allow re-using variable after it
     // has been moved.

src/fn/closures/closure_examples/iter_find.md

@@ -1,8 +1,8 @@
-# Iterator::find
+# Searching through iterators
 
-`Iterator::find` is a function which when passed an iterator, will return
-the first element which satisfies the predicate as an `Option`. Its
-signature:
+`Iterator::find` is a function which iterates over an iterator and searches for the 
+first value which satisfies some condition. If none of the values satisfy the 
+condition, it returns `None`. Its signature:
 
 ```rust,ignore
 pub trait Iterator {
@@ -29,9 +29,11 @@ fn main() {
     // `into_iter()` for vecs yields `i32`.
     let mut into_iter = vec2.into_iter();
 
-    // A reference to what is yielded is `&&i32`. Destructure to `i32`.
+    // `iter()` for vecs yields `&i32`, and we want to reference one of its
+    // items, so we have to destructure `&&i32` to `i32`
     println!("Find 2 in vec1: {:?}", iter     .find(|&&x| x == 2));
-    // A reference to what is yielded is `&i32`. Destructure to `i32`.
+    // `into_iter()` for vecs yields `i32`, and we want to reference one of
+    // its items, so we have to destructure `&i32` to `i32`
     println!("Find 2 in vec2: {:?}", into_iter.find(| &x| x == 2));
 
     let array1 = [1, 2, 3];
@@ -44,8 +46,33 @@ fn main() {
 }
 ```
 
+`Iterator::find` gives you a reference to the item. But if you want the _index_ of the
+item, use `Iterator::position`.
+
+```rust,editable
+fn main() {
+    let vec = vec![1, 9, 3, 3, 13, 2];
+
+    let index_of_first_even_number = vec.iter().position(|x| x % 2 == 0);
+    assert_eq!(index_of_first_even_number, Some(5));
+    
+    
+    let index_of_first_negative_number = vec.iter().position(|x| x < &0);
+    assert_eq!(index_of_first_negative_number, None);
+}
+```
+
 ### See also:
 
 [`std::iter::Iterator::find`][find]
 
+[`std::iter::Iterator::find_map`][find_map]
+
+[`std::iter::Iterator::position`][position]
+
+[`std::iter::Iterator::rposition`][rposition]
+
 [find]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.find
+[find_map]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.find_map
+[position]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.position
+[rposition]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.rposition

src/fn/closures/output_parameters.md

@@ -5,13 +5,11 @@ output parameters should also be possible. However, anonymous
 closure types are, by definition, unknown, so we have to use
 `impl Trait` to return them.
 
-The valid traits for returns are slightly different than before:
+The valid traits for returning a closure are:
 
-* `Fn`: normal
-* `FnMut`: normal
-* `FnOnce`: There are some unusual things at play here, so the [`FnBox`][fnbox]
-  type is currently needed, and is unstable. This is expected to change in
-  the future.
+* `Fn`
+* `FnMut`
+* `FnOnce`
 
 Beyond this, the `move` keyword must be used, which signals that all captures
 occur by value. This is required because any captures by reference would be
@@ -31,12 +29,20 @@ fn create_fnmut() -> impl FnMut() {
     move || println!("This is a: {}", text)
 }
 
+fn create_fnonce() -> impl FnOnce() {
+    let text = "FnOnce".to_owned();
+
+    move || println!("This is a: {}", text)
+}
+
 fn main() {
     let fn_plain = create_fn();
     let mut fn_mut = create_fnmut();
+    let fn_once = create_fnonce();
 
     fn_plain();
     fn_mut();
+    fn_once();
 }
 ```
 
@@ -46,6 +52,5 @@ fn main() {
 
 [fn]: https://doc.rust-lang.org/std/ops/trait.Fn.html
 [fnmut]: https://doc.rust-lang.org/std/ops/trait.FnMut.html
-[fnbox]: https://doc.rust-lang.org/std/boxed/trait.FnBox.html
 [generics]: ../../generics.md
 [impltrait]: ../../trait/impl_trait.md