review feedback

Author: steveklabnik

_posts/2017-10-12-Rust-1.21.md

@@ -35,7 +35,7 @@ In Rust, this code is synonymous with:
 
 ```rust
 let _x = 5;
-let x = &x;
+let x = &_x;
 ```
 
 That is, the `5` here will be stored on the stack, or possibly in registers.
@@ -111,19 +111,19 @@ the platform we build the documentation on. We've long regretted that the hosted
 version of the documentation has been Linux-specific; this is a first step towards
 rectifying that. This is [specific to the standard
 library](https://github.com/rust-lang/rust/pull/43348) and not for general use;
-we'll hope to improve this further in the future.
+we hope to improve this further in the future.
 
 Next, [Cargo's docs are moving!](https://github.com/rust-lang/rust/pull/43916)
 Historically, Cargo's docs were hosted on doc.crates.io, which doesn't follow
-the release train model, even though Cargo itself does. This lead to situations
+the release train model, even though Cargo itself does. This led to situations
 where a feature would land in Cargo nightly, the docs would be updated, and
 then for up to twelve weeks, users would *think* that it should work, but it
 wouldn't yet. [https://doc.rust-lang.org/cargo](https://doc.rust-lang.org/cargo)
 will be the new home of Cargo's docs, though for now, that URL is a redirect to
 doc.crates.io. Future releases will move Cargo's docs over, and at that point,
 doc.crates.io will redirect to doc.rust-lang.org/cargo. Cargo's docs have long
 needed a refreshing, so expect to hear more news about Cargo's docs generally
-through the end of the year.
+in the future!
 
 Finally, until now, `rustdoc` did not have any documentation. This is now
 [fixed](https://github.com/rust-lang/rust/pull/43863), with a new "`rustdoc`
@@ -146,13 +146,50 @@ recently](https://github.com/rust-lang/rfcs/blob/master/text/2000-const-generics
 which may help with this situation. That change has yet to be implemented, however,
 though pre-requisite work is ongoing at the moment.
 
+Next, [`Iterator::for_each`](https://github.com/rust-lang/rust/pull/44567) has
+been stabilized, letting you consume an iterator for side effects without needing
+a `for` loop:
+
+```rust
+// old
+for i in 0..10 {
+    println!("{}", i);
+}
+
+// new
+(0..10).for_each(|i| println!("{}", i));
+```
+
+The correct one to use depends on your situation; in the sample above, the `for` loop
+is pretty striaghtforward. But when you're chaining a number of iterators together,
+the `for_each` version is sometimes clearer. Consider this:
+
+```rust
+// old
+for i in (0..100).map(|x| x + 1).filter(|x| x % 2 == 0) {
+    println!("{}", i);
+}
+
+// new
+(0..100)
+    .map(|x| x + 1)
+    .filter(|x| x % 2 == 0)
+    .for_each(|i| println!("{}", i));
+```
+
 [`Rc<T>` and `Arc<T>` now implement `From<&[T]> where T: Clone`, `From<str>`,
 `From<String>`, `From<Box<T>> where T: ?Sized`, and
 `From<Vec<T>>`.](https://github.com/rust-lang/rust/pull/42565)
 
+The [`max` and `min` functions on the `Ord`
+trait](https://github.com/rust-lang/rust/pull/44593) are now stable.
+
+The [`needs_drop` intrinsic](https://github.com/rust-lang/rust/pull/44639)
+is now stable.
+
 Finally, [`std::mem::discriminant` has been
 stabilized](https://doc.rust-lang.org/std/mem/fn.discriminant.html), allowing
-you to see what variant an `enum` is.
+you to see what variant an `enum` instance is without a `match` statement.
 
 See the [detailed release notes][notes] for more.