[WIP] async and .await chapter

Cargo.toml

@@ -6,6 +6,7 @@ exclude = [
     "linkchecker", # linkchecker is part of the CI workflow
     "listings",    # these are intentionally distinct from the workspace
     "tmp",         # listings are built here when updating output via tools/update-rustc.sh
+    "packages/trpl",        # manages its own dependencies as a standalone crate
 
     # These are used as path dependencies in `rust-lang/rust` (since we are not
     # publishing them to crates.io), so they cannot be part of this workspace,

listings/ch17-async-await/listing-17-01/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "async_await"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

listings/ch17-async-await/listing-17-01/output.txt

@@ -0,0 +1,14 @@
+$ cargo run
+   Compiling async_await v0.1.0 (/Users/chris/dev/rust-lang/book/listings/ch17-async-await/listing-17-01)
+warning: unused implementer of `Future` that must be used
+ --> src/main.rs:3:5
+  |
+3 |     hello("async");
+  |     ^^^^^^^^^^^^^^
+  |
+  = note: futures do nothing unless you `.await` or poll them
+  = note: `#[warn(unused_must_use)]` on by default
+
+warning: `async_await` (bin "async_await") generated 1 warning
+    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.21s
+     Running `target/debug/async_await`

listings/ch17-async-await/listing-17-01/src/main.rs

@@ -0,0 +1,10 @@
+// ANCHOR: all
+fn main() {
+    hello("async");
+}
+
+async fn hello(name: &str) {
+    let greeting = format!("Hello, {name}!");
+    println!("{greeting}");
+}
+// ANCHOR_END: all

listings/ch17-async-await/listing-17-02/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "async_await"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

listings/ch17-async-await/listing-17-02/output.txt

@@ -0,0 +1,12 @@
+$ cargo run
+   Compiling async_await v0.1.0 (/Users/chris/dev/rust-lang/book/listings/ch17-async-await/listing-17-02)
+error[E0728]: `await` is only allowed inside `async` functions and blocks
+ --> src/main.rs:3:20
+  |
+2 | fn main() {
+  |    ---- this is not `async`
+3 |     hello("async").await;
+  |                    ^^^^^ only allowed inside `async` functions and blocks
+
+For more information about this error, try `rustc --explain E0728`.
+error: could not compile `async_await` (bin "async_await") due to 1 previous error

listings/ch17-async-await/listing-17-02/src/main.rs

@@ -0,0 +1,10 @@
+// ANCHOR: main
+fn main() {
+    hello("async").await;
+}
+// ANCHOR_END: main
+
+async fn hello(name: &str) {
+    let greeting = format!("Hello, {name}!");
+    println!("{greeting}");
+}

listings/ch17-async-await/listing-17-03/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "async_await"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

listings/ch17-async-await/listing-17-03/output.txt

@@ -0,0 +1,10 @@
+$ cargo run
+   Compiling async_await v0.1.0 (/Users/chris/dev/rust-lang/book/listings/ch17-async-await/listing-17-03-fix)
+error[E0752]: `main` function is not allowed to be `async`
+ --> src/main.rs:2:1
+  |
+2 | async fn main() {
+  | ^^^^^^^^^^^^^^^ `main` function is not allowed to be `async`
+
+For more information about this error, try `rustc --explain E0752`.
+error: could not compile `async_await` (bin "async_await") due to 1 previous error

listings/ch17-async-await/listing-17-03/src/main.rs

@@ -0,0 +1,10 @@
+// ANCHOR: main
+async fn main() {
+    hello("async").await;
+}
+// ANCHOR_END: main
+
+async fn hello(name: &str) {
+    let greeting = format!("Hello, {name}!");
+    println!("{greeting}");
+}