From f93bc9bad1e1a92328c62947e00e93c92e3b7614 Mon Sep 17 00:00:00 2001
From: xd009642 <danielmckenna93@gmail.com>
Date: Sun, 4 Apr 2021 22:03:00 +0400
Subject: [PATCH] sync: don't panic in oneshot::try_recv (#3674)

---
 tokio/src/sync/oneshot.rs   |  2 +-
 tokio/tests/sync_oneshot.rs | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/tokio/src/sync/oneshot.rs b/tokio/src/sync/oneshot.rs
index a2bf5f9b4..0df6037a1 100644
--- a/tokio/src/sync/oneshot.rs
+++ b/tokio/src/sync/oneshot.rs
@@ -672,7 +672,7 @@ impl<T> Receiver<T> {
                 return Err(TryRecvError::Empty);
             }
         } else {
-            panic!("called after complete");
+            Err(TryRecvError::Closed)
         };
 
         self.inner = None;
diff --git a/tokio/tests/sync_oneshot.rs b/tokio/tests/sync_oneshot.rs
index b1ea46a46..1aab810e1 100644
--- a/tokio/tests/sync_oneshot.rs
+++ b/tokio/tests/sync_oneshot.rs
@@ -2,6 +2,7 @@
 #![cfg(feature = "full")]
 
 use tokio::sync::oneshot;
+use tokio::sync::oneshot::error::TryRecvError;
 use tokio_test::*;
 
 use std::future::Future;
@@ -190,6 +191,17 @@ fn close_after_recv() {
     rx.close();
 }
 
+#[test]
+fn try_recv_after_completion() {
+    let (tx, mut rx) = oneshot::channel::<i32>();
+
+    tx.send(17).unwrap();
+
+    assert_eq!(17, rx.try_recv().unwrap());
+    assert_eq!(Err(TryRecvError::Closed), rx.try_recv());
+    rx.close();
+}
+
 #[test]
 fn drops_tasks() {
     let (mut tx, mut rx) = oneshot::channel::<i32>();