chore: fix ci failure on master (#2593)

* Fix clippy warnings
* Pin rustc version to 1.43.1 in macOS

Refs: https://github.com/rust-lang/rust/issues/73030

ci/azure-test-stable.yml

@@ -5,19 +5,22 @@ jobs:
     matrix:
       Linux:
         vmImage: ubuntu-16.04
+        rust_version: ${{ parameters.rust }}
 
       ${{ if parameters.cross }}:
         MacOS:
           vmImage: macos-latest
+          rust_version: 1.43.1 # https://github.com/rust-lang/rust/issues/73030
         Windows:
           vmImage: vs2017-win2016
+          rust_version: ${{ parameters.rust }}
   pool:
     vmImage: $(vmImage)
 
   steps:
   - template: azure-install-rust.yml
     parameters:
-      rust_version: ${{ parameters.rust }}
+      rust_version: $(rust_version)
 
   - template: azure-is-release.yml
 

examples/echo-udp.rs

@@ -15,7 +15,6 @@
 use std::error::Error;
 use std::net::SocketAddr;
 use std::{env, io};
-use tokio;
 use tokio::net::UdpSocket;
 
 struct Server {

examples/echo.rs

@@ -21,7 +21,6 @@
 
 #![warn(rust_2018_idioms)]
 
-use tokio;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::TcpListener;
 

examples/tinyhttp.rs

@@ -18,7 +18,6 @@ use futures::SinkExt;
 use http::{header::HeaderValue, Request, Response, StatusCode};
 #[macro_use]
 extern crate serde_derive;
-use serde_json;
 use std::{env, error::Error, fmt, io};
 use tokio::net::{TcpListener, TcpStream};
 use tokio::stream::StreamExt;

tokio/src/runtime/thread_pool/worker.rs

@@ -571,7 +571,7 @@ impl Core {
         }
 
         // Drain the queue
-        while let Some(_) = self.next_local_task() {}
+        while self.next_local_task().is_some() {}
     }
 
     fn drain_pending_drop(&mut self, worker: &Worker) {
@@ -793,7 +793,7 @@ impl Shared {
         }
 
         // Drain the injection queue
-        while let Some(_) = self.inject.pop() {}
+        while self.inject.pop().is_some() {}
     }
 
     fn ptr_eq(&self, other: &Shared) -> bool {

tokio/src/sync/batch_semaphore.rs

@@ -519,8 +519,8 @@ impl TryAcquireError {
 impl fmt::Display for TryAcquireError {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            TryAcquireError::Closed => write!(fmt, "{}", "semaphore closed"),
-            TryAcquireError::NoPermits => write!(fmt, "{}", "no permits available"),
+            TryAcquireError::Closed => write!(fmt, "semaphore closed"),
+            TryAcquireError::NoPermits => write!(fmt, "no permits available"),
         }
     }
 }

tokio/src/sync/mutex.rs

@@ -153,7 +153,7 @@ pub struct TryLockError(());
 
 impl fmt::Display for TryLockError {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(fmt, "{}", "operation would block")
+        write!(fmt, "operation would block")
     }
 }
 

tokio/src/sync/semaphore_ll.rs

@@ -854,8 +854,8 @@ impl TryAcquireError {
 impl fmt::Display for TryAcquireError {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            TryAcquireError::Closed => write!(fmt, "{}", "semaphore closed"),
-            TryAcquireError::NoPermits => write!(fmt, "{}", "no permits available"),
+            TryAcquireError::Closed => write!(fmt, "semaphore closed"),
+            TryAcquireError::NoPermits => write!(fmt, "no permits available"),
         }
     }
 }

tokio/tests/rt_basic.rs

@@ -65,7 +65,7 @@ fn no_extra_poll() {
 
     let mut rt = rt();
 
-    rt.spawn(async move { while let Some(_) = rx.next().await {} });
+    rt.spawn(async move { while rx.next().await.is_some() {} });
     rt.block_on(async {
         tokio::task::yield_now().await;
     });

tokio/tests/task_local_set.rs

@@ -365,7 +365,7 @@ fn drop_cancels_remote_tasks() {
         let mut rt = rt();
 
         let local = LocalSet::new();
-        local.spawn_local(async move { while let Some(_) = rx.recv().await {} });
+        local.spawn_local(async move { while rx.recv().await.is_some() {} });
         local.block_on(&mut rt, async {
             time::delay_for(Duration::from_millis(1)).await;
         });

tokio/tests/tcp_accept.rs

@@ -80,7 +80,7 @@ async fn no_extra_poll() {
             s: listener.incoming(),
         };
         assert_ok!(tx.send(Arc::clone(&incoming.npolls)));
-        while let Some(_) = incoming.next().await {
+        while incoming.next().await.is_some() {
             accepted_tx.send(()).unwrap();
         }
     });