review comments

Author: steveklabnik

_posts/2018-10-25-Rust-1.30.md

@@ -132,56 +132,48 @@ This brings macros more in line with other items and removes the need for
 [externmacro]: https://github.com/rust-lang/rust/pull/50911/
 [Rust 1.15]: https://blog.rust-lang.org/2017/02/02/Rust-1.15.html
 
-## Module system improvements
-
-The module system has long been a pain point of new Rustaceans; several of
-its rules felt awkward in practice. These changes are the first steps we're
-taking to make the module system feel more straightforward.
+Finally, the [`proc_macro` crate](https://doc.rust-lang.org/stable/proc_macro/)
+is made stable, which gives you the needed APIs to write these sorts of macros.
+It also has significantly improved the APIs for errors, and crates like `syn` and
+`quote` are already using them. For example, before:
 
-[`mod.rs` files are now optional][optionalmod]. Imagine we had a `foo`
-submodule with a `bar` submodule of its own. The directory layout would
-look like this:
-
-```text
-.
-├── src
-│   ├── foo
-│   │   └── mod.rs
-│   │   └── bar.rs
-│   └── lib.rs
+```rust,ignore
+#[derive(Serialize)]
+struct Demo {
+    ok: String,
+    bad: std::thread::Thread,
+}
 ```
 
-In Rust 1.30, you can do this instead:
+used to give this error:
 
 ```text
-.
-├── src
-│   ├── foo
-│   │   └── bar.rs
-│   ├── foo.rs
-│   └── lib.rs
+error[E0277]: the trait bound `std::thread::Thread: _IMPL_SERIALIZE_FOR_Demo::_serde::Serialize` is not satisfied
+ --> src/main.rs:3:10
+  |
+3 | #[derive(Serialize)]
+  |          ^^^^^^^^^ the trait `_IMPL_SERIALIZE_FOR_Demo::_serde::Serialize` is not implemented for `std::thread::Thread`
 ```
 
-This means that you'll no longer have plenty of tabs all named `mod.rs` in
-your IDE! It also eases the process of adding a submodule; before `bar`
-existed, the project would look like this:
+Now it will give this one:
 
 ```text
-.
-├── src
-│   ├── foo.rs
-│   └── lib.rs
+error[E0277]: the trait bound `std::thread::Thread: serde::Serialize` is not satisfied
+ --> src/main.rs:7:5
+  |
+7 |     bad: std::thread::Thread,
+  |     ^^^ the trait `serde::Serialize` is not implemented for `std::thread::Thread`
 ```
 
-Many users found the need to move `foo.rs` into `foo/mod.rs` to be an
-unncessary, strage requirement. With the new layout, you create `src/foo`,
-put `bar.rs` in it, and you're done.
+## Module system improvements
 
-[optionalmod]: https://github.com/rust-lang/rust/pull/54072
+The module system has long been a pain point of new Rustaceans; several of
+its rules felt awkward in practice. These changes are the first steps we're
+taking to make the module system feel more straightforward.
 
-There's two changes to `use` as well, in addition to the aforementioned change for
-macros. The first is that you can now always [`use` an extern crate without
-`::`][nocoloncolon], that is:
+There's two changes to `use` in addition to the aforementioned change for
+macros. The first is that [external crates are now in the
+prelude][nocoloncolon], that is:
 
 ```rust
 // old
@@ -313,13 +305,26 @@ Rust 2018.
 
 [rawidents]: https://github.com/rust-lang/rust/pull/53236/
 
-## Other things
+## `no_std` applications
 
-Finally, you can [use the `#[panic_handler]`][panichandler] attribute to
-implement panics yourself, and you can now [match on visibility keywords,
-like `pub`, in macros][viskeyword] using the `vis` specifier.
+Back in Rust 1.6, we announced the [stabilization of `no_std` and
+`libcore`](https://blog.rust-lang.org/2016/01/21/Rust-1.6.html) for building
+projects without the standard library. There was a twist, though: you could
+only build libraries, but not applications.
+
+With Rust 1.30, you can [use the `#[panic_handler]`][panichandler] attribute
+to implement panics yourself. This now means that you can build applications,
+not just libraries, that don't use the standard library.
 
 [panichandler]: https://github.com/rust-lang/rust/pull/51366/
+## Other things
+
+Finally, you can now [match on visibility keywords, like `pub`, in
+macros][viskeyword] using the `vis` specifier. Additionally, "tool
+attributes" like `#[rustfmt::skip]` [are now
+stable](https://github.com/rust-lang/rust/pull/53459/). Tool *lints*
+like `#[allow(clippy::something)]` are not yet stable, however.
+
 [viskeyword]: https://github.com/rust-lang/rust/pull/53370/
 
 See the [detailed release notes][notes] for more.