Add Mutex::try_lock and (Unbounded)Receiver::try_recv (#1939)

tokio/tests/sync_mpsc.rs

@@ -2,7 +2,7 @@
 #![cfg(feature = "full")]
 
 use tokio::sync::mpsc;
-use tokio::sync::mpsc::error::TrySendError;
+use tokio::sync::mpsc::error::{TryRecvError, TrySendError};
 use tokio_test::task;
 use tokio_test::{
     assert_err, assert_ok, assert_pending, assert_ready, assert_ready_err, assert_ready_ok,
@@ -413,3 +413,41 @@ fn unconsumed_messages_are_dropped() {
 
     assert_eq!(1, Arc::strong_count(&msg));
 }
+
+#[test]
+fn try_recv() {
+    let (mut tx, mut rx) = mpsc::channel(1);
+    match rx.try_recv() {
+        Err(TryRecvError::Empty) => {}
+        _ => panic!(),
+    }
+    tx.try_send(42).unwrap();
+    match rx.try_recv() {
+        Ok(42) => {}
+        _ => panic!(),
+    }
+    drop(tx);
+    match rx.try_recv() {
+        Err(TryRecvError::Closed) => {}
+        _ => panic!(),
+    }
+}
+
+#[test]
+fn try_recv_unbounded() {
+    let (tx, mut rx) = mpsc::unbounded_channel();
+    match rx.try_recv() {
+        Err(TryRecvError::Empty) => {}
+        _ => panic!(),
+    }
+    tx.send(42).unwrap();
+    match rx.try_recv() {
+        Ok(42) => {}
+        _ => panic!(),
+    }
+    drop(tx);
+    match rx.try_recv() {
+        Err(TryRecvError::Closed) => {}
+        _ => panic!(),
+    }
+}

tokio/tests/sync_mutex.rs

@@ -134,3 +134,16 @@ async fn aborted_future_2() {
     .await
     .expect("Mutex is locked");
 }
+
+#[test]
+fn try_lock() {
+    let m: Mutex<usize> = Mutex::new(0);
+    {
+        let g1 = m.try_lock();
+        assert_eq!(g1.is_ok(), true);
+        let g2 = m.try_lock();
+        assert_eq!(g2.is_ok(), false);
+    }
+    let g3 = m.try_lock();
+    assert_eq!(g3.is_ok(), true);
+}