Stylist nitpicks

Author: Urgau

posts/2024-05-05-check-cfg.md

@@ -5,9 +5,7 @@ author: Urgau
 team: The Cargo Team <https://www.rust-lang.org/governance/teams/dev-tools#cargo>
 ---
 
-# Automatic checking of cfgs at compile-time
-
-The Cargo and Compiler team are delighted to announce that starting with Rust 1.80 (or nightly-2024-05-05) every _reachable_ `#[cfg]` will be automatically checked that they match the expected config names and values.
+The Cargo and Compiler team are delighted to announce that starting with Rust 1.80 (or nightly-2024-05-05) every _reachable_ `#[cfg]` will be **automatically checked** that they match the **expected config names and values**.
 
 This can help with verifying that the crate is correctly handling conditional compilation for different target platforms or features. It ensures that the cfg settings are consistent between what is intended and what is used, helping to catch potential bugs or errors early in the development process.
 
@@ -33,34 +31,40 @@ zapping = []
 ```
 
 *`src/lib.rs`:*
+
 ```rust
 #[cfg(feature = "lasers")]  // This condition is expected
-                            //   as "lasers" is an expected value of `feature`
+                            // as "lasers" is an expected value
+                            // of the `feature` cfg
 fn shoot_lasers() {}
 
 #[cfg(feature = "monkeys")] // This condition is UNEXPECTED
-                            //   as "monkeys" is NOT an expected value of `feature`
+                            // as "monkeys" is NOT an expected
+                            // value of the `feature` cfg
 fn write_shakespeare() {}
 
 #[cfg(windosw)]             // This condition is UNEXPECTED
-                            //   it's supposed to be `windows`
+                            // it's supposed to be `windows`
 fn win() {}
 ```
 
 *`cargo check`*:
+
 ![cargo-check](../../../../images/2024-05-05-check-cfg/cargo-check.svg)
 
 ## Custom cfgs and build scripts
 
-> In Cargo point-of-view: a custom cfg is one that is neither defined by `rustc` nor by a Cargo feature. Think of `tokio_unstable`, `has_foo`, ... but not `feature = "lasers"`, `unix`, ...
+> In Cargo point-of-view: a custom cfg is one that is neither defined by `rustc` nor by a Cargo feature. Think of `tokio_unstable`, `has_foo`, ... but not `feature = "lasers"`, `unix` or `debug_assertions`
 
 Some crates use custom cfgs that they either expected from the environment (`RUSTFLAGS`or other means) or is enabled by some logic in the crate `build.rs`. For those crates Cargo provides a new instruction: [`cargo::rustc-check-cfg`](https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg)[^2] (or `cargo:rustc-check-cfg` for older Cargo version).
 
 [^2]: `cargo::rustc-check-cfg` will start working in Rust 1.80 (or nightly-2024-05-05). From Rust 1.77 to Rust 1.79 *(inclusive)* it is silently ignored. In Rust 1.76 and below a warning is emitted when used without the unstable Cargo flag `-Zcheck-cfg`.
 
 The syntax to use is described in the [rustc book](https://doc.rust-lang.org/nightly/rustc/) section [checking configuration](https://doc.rust-lang.org/nightly/rustc/check-cfg.html), but in a nutshell the basic syntax of `--check-cfg` is:
 
-> `cfg(name, values("value1", "value2", ..., "valueN"))`
+```
+cfg(name, values("value1", "value2", ..., "valueN"))
+```
 
 Note that every custom cfgs must always be expected, regardless if the cfg is active or not!
 
@@ -69,7 +73,8 @@ Note that every custom cfgs must always be expected, regardless if the cfg is ac
 `build.rs`:
 ```rust
 fn main() {
-    println!("cargo::rustc-check-cfg=cfg(has_foo)"); // <-- new with Cargo 1.80
+    println!("cargo::rustc-check-cfg=cfg(has_foo)");
+    //        ^^^^^^^^^^^^^^^^^^^^^^ new with Cargo 1.80
     if has_foo() {
         println!("cargo::rustc-cfg=has_foo");
     }
@@ -95,7 +100,7 @@ More details can be found in the [`rustc` book](https://doc.rust-lang.org/nightl
 
 ### Can it be disabled?
 
-The feature is **always on** and _cannot_ be disabled from Cargo, but like any other lints it can be controlled: `#![allow(unexpected_cfgs)]`.
+The feature is **always on** and _cannot_ be disabled from Cargo, but like any other lints it can be controlled: `#![warn(unexpected_cfgs)]`.
 
 ### Does the lint affect dependencies?