Addressing aturon's nits

Author: carols10cents

_posts/2017-06-08-Rust-1.18.md

@@ -22,8 +22,8 @@ appropriate page on our website, and check out the [detailed release notes for
 
 ### What's in 1.18.0 stable
 
-Rust 1.18.0 is similar to many of our releases: no big surprises, just a number
-of improvements, cleanups, and new features.
+As usual, Rust 1.18.0 is a collection of improvements, cleanups, and new
+features.
 
 One of the largest changes is a long time coming: core team members Carol
 Nichols and Steve Klabnik have been writing a new edition of "The Rust
@@ -35,11 +35,13 @@ edition in our online documentation](https://doc.rust-lang.org/stable/book/).
 1.19. When the book is done, a print version will be made available through [No
 Starch Press](https://www.nostarch.com/Rust), if you'd like a paper copy. We're
 still working with the editors at No Starch to improve the text, but we wanted
-to start getting a wider audience now. The new edition is a complete re-write
-from the ground up, using the last two years of knowledge we've gained from
-teaching people Rust. You'll find brand-new explanations for a lot of Rust's
-core concepts, new projects to build, and all kinds of other good stuff. Please
-check it out and [let us know what you think](https://github.com/rust-lang/book/issues/new)!
+to start getting a wider audience now.
+
+The new edition is a complete re-write from the ground up, using the last two
+years of knowledge we've gained from teaching people Rust. You'll find
+brand-new explanations for a lot of Rust's core concepts, new projects to
+build, and all kinds of other good stuff. Please check it out and [let us know
+what you think](https://github.com/rust-lang/book/issues/new)!
 
 As for the language itself, an old feature has learned some new tricks: the
 `pub` keyword has been expanded a bit. Experienced Rustaceans will know that
@@ -55,7 +57,8 @@ The bit inside of `()` is a 'restriction', which refines the notion of how this
 is made public. Using the `crate` keyword like the example above means that
 `bar` would be public to the entire crate, but not outside of it. This makes it
 easier to declare APIs that are "public to your crate", but not exposed to your
-users. This was *possible* with the current module system, but often very awkward.
+users. This was *possible* with the existing module system, but often very
+awkward.
 
 You can also specify a path, like this:
 
@@ -107,44 +110,22 @@ But what if our struct looked like this?
 struct Optimal(u8, u8, u16);
 ```
 
-This struct is properly aligned; the `u16` lies on a two byte boundary, and so does
-the entire struct. No padding is needed. This gives us `1 + 1 + 2 = 4 bytes`.
-
-When designing Rust, stuff like this is why we left the details here undefined.
-It allows for exactly this kind of thing: the compiler can optimize `Suboptimal`
-into `Optimal` automatically. And if you check the sizes of `Suboptimal` and
-`Optimal` on Rust 1.18.0, you'll see that they both have a size of four bytes.
-
-We've been planning this for a while; previous versions of Rust included this
-optimization on the nightly channel, but some people wrote unsafe code that
-assumed the exact details of the representation. We rolled it back while we fixed
-all instances of this that we know about, but if you find some code breaks due to
-this, you should fix it! In the meantime, there's also a flag you can use to control
-this. Imagine we have `Suboptimal` in a file named `foo.rs`, along with a `main`
-function that prints out its size:
-
-```rust
-> rustc foo.rs
-> ./foo
-4
-> rustc foo.rs -Z fuel=foo=0
-optimization-fuel-exhausted: Reorder fields of "Suboptimal"
-> ./foo
-6
-```
-
-This flag is based on an idea called "[Optimization
-fuel](https://www.microsoft.com/en-us/research/wp-content/uploads/2016/07/dfopt-popl10.pdf)":
+This struct is properly aligned; the `u16` lies on a two byte boundary, and so
+does the entire struct. No padding is needed. This gives us `1 + 1 + 2 = 4
+bytes`.
 
-> It works by giving the optimizer a finite supply of optimization fuel. Each
-> time a rewrite function proposes to replace a node, one unit of fuel is
-> consumed. When the optimizer runs out of fuel, further rewrites are
-> suppressed.
+When designing Rust, we left the details of memory layout undefined for just
+this reason. Because we didn't commit to a particular layout, we can make
+improvements to it, such as in this case where the compiler can optimize
+`Suboptimal` into `Optimal` automatically. And if you check the sizes of
+`Suboptimal` and `Optimal` on Rust 1.18.0, you'll see that they both have a
+size of four bytes.
 
-Currently, this is the only optimization that uses the "fuel" concept. By
-setting the fuel to zero, `rustc` will not perform the optimization. This can
-keep your code compiling if you run into a problem, but the longer-term fix is
-to use a `#[repr]` attribute to guarantee a particular layout if you rely on it.
+We've been planning this change for a while; previous versions of Rust included
+this optimization on the nightly channel, but some people wrote unsafe code
+that assumed the exact details of the representation. We rolled it back while
+we fixed all instances of this that we know about, but if you find some code
+breaks due to this, please let us know so we can help fix it!
 
 We've been planning on moving `rustdoc` to use a CommonMark compliant markdown
 parser for a long time now. However, just switching over can introduce
@@ -158,8 +139,8 @@ rendered results differ!
 
 Finally, compiling `rustc` itself is now [15%-20%
 faster](https://github.com/rust-lang/rust/pull/41469). Each commit message in
-this PR goes over the details, but the short of it is that there were some
-inefficient things, and now they've been cleaned up.
+this PR goes over the details; there were some inefficiencies, and now they've
+been cleaned up.
 
 See the [detailed release notes][notes] for more.