tokio: avoid positional fmt params when possible (#6978)

benches/sync_mpsc.rs

@@ -37,7 +37,7 @@ fn create_medium<const SIZE: usize>(g: &mut BenchmarkGroup<WallTime>) {
 fn send_data<T: Default, const SIZE: usize>(g: &mut BenchmarkGroup<WallTime>, prefix: &str) {
     let rt = rt();
 
-    g.bench_function(format!("{}_{}", prefix, SIZE), |b| {
+    g.bench_function(format!("{prefix}_{SIZE}"), |b| {
         b.iter(|| {
             let (tx, mut rx) = mpsc::channel::<T>(SIZE);
 

examples/chat.rs

@@ -193,7 +193,7 @@ async fn process(
     // A client has connected, let's let everyone know.
     {
         let mut state = state.lock().await;
-        let msg = format!("{} has joined the chat", username);
+        let msg = format!("{username} has joined the chat");
         tracing::info!("{}", msg);
         state.broadcast(addr, &msg).await;
     }
@@ -210,7 +210,7 @@ async fn process(
                 // broadcast this message to the other users.
                 Some(Ok(msg)) => {
                     let mut state = state.lock().await;
-                    let msg = format!("{}: {}", username, msg);
+                    let msg = format!("{username}: {msg}");
 
                     state.broadcast(addr, &msg).await;
                 }
@@ -234,7 +234,7 @@ async fn process(
         let mut state = state.lock().await;
         state.peers.remove(&addr);
 
-        let msg = format!("{} has left the chat", username);
+        let msg = format!("{username} has left the chat");
         tracing::info!("{}", msg);
         state.broadcast(addr, &msg).await;
     }

examples/connect.rs

@@ -77,7 +77,7 @@ mod tcp {
                 //BytesMut into Bytes
                 Ok(i) => future::ready(Some(i.freeze())),
                 Err(e) => {
-                    println!("failed to read from socket; error={}", e);
+                    println!("failed to read from socket; error={e}");
                     future::ready(None)
                 }
             })

examples/echo-udp.rs

@@ -38,7 +38,7 @@ impl Server {
             if let Some((size, peer)) = to_send {
                 let amt = socket.send_to(&buf[..size], &peer).await?;
 
-                println!("Echoed {}/{} bytes to {}", amt, size, peer);
+                println!("Echoed {amt}/{size} bytes to {peer}");
             }
 
             // If we're here then `to_send` is `None`, so we take a look for the

examples/echo.rs

@@ -40,7 +40,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
     // connections. This TCP listener is bound to the address we determined
     // above and must be associated with an event loop.
     let listener = TcpListener::bind(&addr).await?;
-    println!("Listening on: {}", addr);
+    println!("Listening on: {addr}");
 
     loop {
         // Asynchronously wait for an inbound socket.

examples/print_each_packet.rs

@@ -75,7 +75,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     // to our event loop. After the socket's created we inform that we're ready
     // to go and start accepting connections.
     let listener = TcpListener::bind(&addr).await?;
-    println!("Listening on: {}", addr);
+    println!("Listening on: {addr}");
 
     loop {
         // Asynchronously wait for an inbound socket.
@@ -96,8 +96,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             // The stream will return None once the client disconnects.
             while let Some(message) = framed.next().await {
                 match message {
-                    Ok(bytes) => println!("bytes: {:?}", bytes),
-                    Err(err) => println!("Socket closed with error: {:?}", err),
+                    Ok(bytes) => println!("bytes: {bytes:?}"),
+                    Err(err) => println!("Socket closed with error: {err:?}"),
                 }
             }
             println!("Socket received FIN packet and closed connection");

examples/proxy.rs

@@ -38,8 +38,8 @@ async fn main() -> Result<(), Box<dyn Error>> {
         .nth(2)
         .unwrap_or_else(|| "127.0.0.1:8080".to_string());
 
-    println!("Listening on: {}", listen_addr);
-    println!("Proxying to: {}", server_addr);
+    println!("Listening on: {listen_addr}");
+    println!("Proxying to: {server_addr}");
 
     let listener = TcpListener::bind(listen_addr).await?;
 
@@ -50,7 +50,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
             copy_bidirectional(&mut inbound, &mut outbound)
                 .map(|r| {
                     if let Err(e) = r {
-                        println!("Failed to transfer; error={}", e);
+                        println!("Failed to transfer; error={e}");
                     }
                 })
                 .await

examples/tinydb.rs

@@ -90,7 +90,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
         .unwrap_or_else(|| "127.0.0.1:8080".to_string());
 
     let listener = TcpListener::bind(&addr).await?;
-    println!("Listening on: {}", addr);
+    println!("Listening on: {addr}");
 
     // Create the shared state of this server that will be shared amongst all
     // clients. We populate the initial database and then create the `Database`
@@ -131,19 +131,19 @@ async fn main() -> Result<(), Box<dyn Error>> {
                                 let response = response.serialize();
 
                                 if let Err(e) = lines.send(response.as_str()).await {
-                                    println!("error on sending response; error = {:?}", e);
+                                    println!("error on sending response; error = {e:?}");
                                 }
                             }
                             Err(e) => {
-                                println!("error on decoding from socket; error = {:?}", e);
+                                println!("error on decoding from socket; error = {e:?}");
                             }
                         }
                     }
 
                     // The connection will be closed at this point as `lines.next()` has returned `None`.
                 });
             }
-            Err(e) => println!("error accepting socket; error = {:?}", e),
+            Err(e) => println!("error accepting socket; error = {e:?}"),
         }
     }
 }
@@ -162,7 +162,7 @@ fn handle_request(line: &str, db: &Arc<Database>) -> Response {
                 value: value.clone(),
             },
             None => Response::Error {
-                msg: format!("no key {}", key),
+                msg: format!("no key {key}"),
             },
         },
         Request::Set { key, value } => {
@@ -203,7 +203,7 @@ impl Request {
                     value: value.to_string(),
                 })
             }
-            Some(cmd) => Err(format!("unknown command: {}", cmd)),
+            Some(cmd) => Err(format!("unknown command: {cmd}")),
             None => Err("empty input".into()),
         }
     }
@@ -212,13 +212,13 @@ impl Request {
 impl Response {
     fn serialize(&self) -> String {
         match *self {
-            Response::Value { ref key, ref value } => format!("{} = {}", key, value),
+            Response::Value { ref key, ref value } => format!("{key} = {value}"),
             Response::Set {
                 ref key,
                 ref value,
                 ref previous,
-            } => format!("set {} = `{}`, previous: {:?}", key, value, previous),
-            Response::Error { ref msg } => format!("error: {}", msg),
+            } => format!("set {key} = `{value}`, previous: {previous:?}"),
+            Response::Error { ref msg } => format!("error: {msg}"),
         }
     }
 }

examples/tinyhttp.rs

@@ -31,13 +31,13 @@ async fn main() -> Result<(), Box<dyn Error>> {
         .nth(1)
         .unwrap_or_else(|| "127.0.0.1:8080".to_string());
     let server = TcpListener::bind(&addr).await?;
-    println!("Listening on: {}", addr);
+    println!("Listening on: {addr}");
 
     loop {
         let (stream, _) = server.accept().await?;
         tokio::spawn(async move {
             if let Err(e) = process(stream).await {
-                println!("failed to process connection; error = {}", e);
+                println!("failed to process connection; error = {e}");
             }
         });
     }
@@ -159,7 +159,7 @@ impl Decoder for Http {
             let mut parsed_headers = [httparse::EMPTY_HEADER; 16];
             let mut r = httparse::Request::new(&mut parsed_headers);
             let status = r.parse(src).map_err(|e| {
-                let msg = format!("failed to parse http request: {:?}", e);
+                let msg = format!("failed to parse http request: {e:?}");
                 io::Error::new(io::ErrorKind::Other, msg)
             })?;
 

examples/udp-codec.rs

@@ -46,7 +46,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     // Run both futures simultaneously of `a` and `b` sending messages back and forth.
     match tokio::try_join!(a, b) {
-        Err(e) => println!("an error occurred; error = {:?}", e),
+        Err(e) => println!("an error occurred; error = {e:?}"),
         _ => println!("done!"),
     }
 

tokio-macros/src/entry.rs

@@ -20,7 +20,7 @@ impl RuntimeFlavor {
             "single_thread" => Err("The single threaded runtime flavor is called `current_thread`.".to_string()),
             "basic_scheduler" => Err("The `basic_scheduler` runtime flavor has been renamed to `current_thread`.".to_string()),
             "threaded_scheduler" => Err("The `threaded_scheduler` runtime flavor has been renamed to `multi_thread`.".to_string()),
-            _ => Err(format!("No such runtime flavor `{}`. The runtime flavors are `current_thread` and `multi_thread`.", s)),
+            _ => Err(format!("No such runtime flavor `{s}`. The runtime flavors are `current_thread` and `multi_thread`.")),
         }
     }
 }
@@ -36,7 +36,7 @@ impl UnhandledPanic {
         match s {
             "ignore" => Ok(UnhandledPanic::Ignore),
             "shutdown_runtime" => Ok(UnhandledPanic::ShutdownRuntime),
-            _ => Err(format!("No such unhandled panic behavior `{}`. The unhandled panic behaviors are `ignore` and `shutdown_runtime`.", s)),
+            _ => Err(format!("No such unhandled panic behavior `{s}`. The unhandled panic behaviors are `ignore` and `shutdown_runtime`.")),
         }
     }
 
@@ -239,12 +239,12 @@ fn parse_int(int: syn::Lit, span: Span, field: &str) -> Result<usize, syn::Error
             Ok(value) => Ok(value),
             Err(e) => Err(syn::Error::new(
                 span,
-                format!("Failed to parse value of `{}` as integer: {}", field, e),
+                format!("Failed to parse value of `{field}` as integer: {e}"),
             )),
         },
         _ => Err(syn::Error::new(
             span,
-            format!("Failed to parse value of `{}` as integer.", field),
+            format!("Failed to parse value of `{field}` as integer."),
         )),
     }
 }
@@ -255,7 +255,7 @@ fn parse_string(int: syn::Lit, span: Span, field: &str) -> Result<String, syn::E
         syn::Lit::Verbatim(s) => Ok(s.to_string()),
         _ => Err(syn::Error::new(
             span,
-            format!("Failed to parse value of `{}` as string.", field),
+            format!("Failed to parse value of `{field}` as string."),
         )),
     }
 }
@@ -275,7 +275,7 @@ fn parse_path(lit: syn::Lit, span: Span, field: &str) -> Result<Path, syn::Error
         }
         _ => Err(syn::Error::new(
             span,
-            format!("Failed to parse value of `{}` as path.", field),
+            format!("Failed to parse value of `{field}` as path."),
         )),
     }
 }
@@ -285,7 +285,7 @@ fn parse_bool(bool: syn::Lit, span: Span, field: &str) -> Result<bool, syn::Erro
         syn::Lit::Bool(b) => Ok(b.value),
         _ => Err(syn::Error::new(
             span,
-            format!("Failed to parse value of `{}` as bool.", field),
+            format!("Failed to parse value of `{field}` as bool."),
         )),
     }
 }
@@ -342,8 +342,7 @@ fn build_config(
                     }
                     name => {
                         let msg = format!(
-                            "Unknown attribute {} is specified; expected one of: `flavor`, `worker_threads`, `start_paused`, `crate`, `unhandled_panic`",
-                            name,
+                            "Unknown attribute {name} is specified; expected one of: `flavor`, `worker_threads`, `start_paused`, `crate`, `unhandled_panic`",
                         );
                         return Err(syn::Error::new_spanned(namevalue, msg));
                     }
@@ -358,21 +357,19 @@ fn build_config(
                 let msg = match name.as_str() {
                     "threaded_scheduler" | "multi_thread" => {
                         format!(
-                            "Set the runtime flavor with #[{}(flavor = \"multi_thread\")].",
-                            macro_name
+                            "Set the runtime flavor with #[{macro_name}(flavor = \"multi_thread\")]."
                         )
                     }
                     "basic_scheduler" | "current_thread" | "single_threaded" => {
                         format!(
-                            "Set the runtime flavor with #[{}(flavor = \"current_thread\")].",
-                            macro_name
+                            "Set the runtime flavor with #[{macro_name}(flavor = \"current_thread\")]."
                         )
                     }
                     "flavor" | "worker_threads" | "start_paused" | "crate" | "unhandled_panic" => {
-                        format!("The `{}` attribute requires an argument.", name)
+                        format!("The `{name}` attribute requires an argument.")
                     }
                     name => {
-                        format!("Unknown attribute {} is specified; expected one of: `flavor`, `worker_threads`, `start_paused`, `crate`, `unhandled_panic`.", name)
+                        format!("Unknown attribute {name} is specified; expected one of: `flavor`, `worker_threads`, `start_paused`, `crate`, `unhandled_panic`.")
                     }
                 };
                 return Err(syn::Error::new_spanned(path, msg));

tokio-macros/src/select.rs

@@ -11,7 +11,7 @@ pub(crate) fn declare_output_enum(input: TokenStream) -> TokenStream {
     };
 
     let variants = (0..branches)
-        .map(|num| Ident::new(&format!("_{}", num), Span::call_site()))
+        .map(|num| Ident::new(&format!("_{num}"), Span::call_site()))
         .collect::<Vec<_>>();
 
     // Use a bitfield to track which futures completed

tokio-test/src/stream_mock.rs

@@ -161,8 +161,7 @@ impl<T: Unpin> Drop for StreamMock<T> {
 
         assert!(
             undropped_count == 0,
-            "StreamMock was dropped before all actions were consumed, {} actions were not consumed",
-            undropped_count
+            "StreamMock was dropped before all actions were consumed, {undropped_count} actions were not consumed"
         );
     }
 }

tokio-test/tests/io.rs

@@ -34,7 +34,7 @@ async fn read_error() {
     match mock.read(&mut buf).await {
         Err(error) => {
             assert_eq!(error.kind(), io::ErrorKind::Other);
-            assert_eq!("cruel", format!("{}", error));
+            assert_eq!("cruel", format!("{error}"));
         }
         Ok(_) => panic!("error not received"),
     }
@@ -87,7 +87,7 @@ async fn write_error() {
     match mock.write_all(b"whoa").await {
         Err(error) => {
             assert_eq!(error.kind(), io::ErrorKind::Other);
-            assert_eq!("cruel", format!("{}", error));
+            assert_eq!("cruel", format!("{error}"));
         }
         Ok(_) => panic!("error not received"),
     }

tokio-util/src/codec/any_delimiter_codec.rs

@@ -249,7 +249,7 @@ impl fmt::Display for AnyDelimiterCodecError {
             AnyDelimiterCodecError::MaxChunkLengthExceeded => {
                 write!(f, "max chunk length exceeded")
             }
-            AnyDelimiterCodecError::Io(e) => write!(f, "{}", e),
+            AnyDelimiterCodecError::Io(e) => write!(f, "{e}"),
         }
     }
 }

tokio-util/src/codec/lines_codec.rs

@@ -218,7 +218,7 @@ impl fmt::Display for LinesCodecError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             LinesCodecError::MaxLineLengthExceeded => write!(f, "max line length exceeded"),
-            LinesCodecError::Io(e) => write!(f, "{}", e),
+            LinesCodecError::Io(e) => write!(f, "{e}"),
         }
     }
 }

tokio-util/src/task/spawn_pinned.rs

@@ -249,7 +249,7 @@ impl LocalPool {
             // Send the callback to the LocalSet task
             if let Err(e) = worker_spawner.send(spawn_task) {
                 // Propagate the error as a panic in the join handle.
-                panic!("Failed to send job to worker: {}", e);
+                panic!("Failed to send job to worker: {e}");
             }
 
             // Wait for the task's join handle
@@ -260,7 +260,7 @@ impl LocalPool {
                     // join handle... We assume something happened to the worker
                     // and the task was not spawned. Propagate the error as a
                     // panic in the join handle.
-                    panic!("Worker failed to send join handle: {}", e);
+                    panic!("Worker failed to send join handle: {e}");
                 }
             };
 
@@ -284,12 +284,12 @@ impl LocalPool {
                         // No one else should have the join handle, so this is
                         // unexpected. Forward this error as a panic in the join
                         // handle.
-                        panic!("spawn_pinned task was canceled: {}", e);
+                        panic!("spawn_pinned task was canceled: {e}");
                     } else {
                         // Something unknown happened (not a panic or
                         // cancellation). Forward this error as a panic in the
                         // join handle.
-                        panic!("spawn_pinned task failed: {}", e);
+                        panic!("spawn_pinned task failed: {e}");
                     }
                 }
             }

tokio-util/src/time/delay_queue.rs

@@ -665,7 +665,7 @@ impl<T> DelayQueue<T> {
                 // The delay is already expired, store it in the expired queue
                 self.expired.push(key, &mut self.slab);
             }
-            Err((_, err)) => panic!("invalid deadline; err={:?}", err),
+            Err((_, err)) => panic!("invalid deadline; err={err:?}"),
         }
     }