Merge #968

968: channel: Extend panic_on_drop test r=taiki-e a=taiki-e

Include rust-lang/rust#107466 's case.
cc rust-lang/rust#108164


Co-authored-by: Taiki Endo <te316e89@gmail.com>

Author: bors[bot]

crossbeam-channel/tests/array.rs

@@ -1,6 +1,7 @@
 //! Tests for the array channel flavor.
 
 use std::any::Any;
+use std::cell::Cell;
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering;
 use std::thread;
@@ -692,53 +693,95 @@ fn channel_through_channel() {
 
 #[test]
 fn panic_on_drop() {
-    struct Msg1<'a>(&'a mut bool);
+    struct Msg1<'a>(&'a Cell<bool>);
     impl Drop for Msg1<'_> {
         fn drop(&mut self) {
-            if *self.0 && !std::thread::panicking() {
+            if self.0.get() && !std::thread::panicking() {
                 panic!("double drop");
             } else {
-                *self.0 = true;
+                self.0.set(true);
             }
         }
     }
 
-    struct Msg2<'a>(&'a mut bool);
+    struct Msg2<'a>(&'a Cell<bool>);
     impl Drop for Msg2<'_> {
         fn drop(&mut self) {
-            if *self.0 {
+            if self.0.get() {
                 panic!("double drop");
             } else {
-                *self.0 = true;
+                self.0.set(true);
                 panic!("first drop");
             }
         }
     }
 
-    // normal
+    // normal (sender first)
     let (s, r) = bounded(2);
-    let (mut a, mut b) = (false, false);
-    s.send(Msg1(&mut a)).unwrap();
-    s.send(Msg1(&mut b)).unwrap();
+    let (a, b) = (Cell::new(false), Cell::new(false));
+    s.send(Msg1(&a)).unwrap();
+    s.send(Msg1(&b)).unwrap();
     drop(s);
+    assert!(!a.get());
+    assert!(!b.get());
     drop(r);
-    assert!(a);
-    assert!(b);
+    assert!(a.get());
+    assert!(b.get());
 
-    // panic on drop
+    // normal (receiver first)
     let (s, r) = bounded(2);
-    let (mut a, mut b) = (false, false);
-    s.send(Msg2(&mut a)).unwrap();
-    s.send(Msg2(&mut b)).unwrap();
+    let (a, b) = (Cell::new(false), Cell::new(false));
+    s.send(Msg1(&a)).unwrap();
+    s.send(Msg1(&b)).unwrap();
+    drop(r);
+    // TODO: should be dropped eagerly: https://github.com/rust-lang/rust/issues/107466
+    assert!(!a.get());
+    assert!(!b.get());
     drop(s);
+    assert!(a.get());
+    assert!(b.get());
+
+    // panic on drop (sender first)
+    let (s, r) = bounded(2);
+    let (a, b) = (Cell::new(false), Cell::new(false));
+    s.send(Msg2(&a)).unwrap();
+    s.send(Msg2(&b)).unwrap();
+    drop(s);
+    assert!(!a.get());
+    assert!(!b.get());
     let res = std::panic::catch_unwind(move || {
         drop(r);
     });
     assert_eq!(
         *res.unwrap_err().downcast_ref::<&str>().unwrap(),
         "first drop"
     );
-    assert!(a);
+    assert!(a.get());
+    // Elements after the panicked element will leak.
+    assert!(!b.get());
+
+    // panic on drop (receiver first)
+    let (s, r) = bounded(2);
+    let (a, b) = (Cell::new(false), Cell::new(false));
+    s.send(Msg2(&a)).unwrap();
+    s.send(Msg2(&b)).unwrap();
+    let res = std::panic::catch_unwind(move || {
+        drop(r);
+    });
+    // This currently doesn't panic, but it should panic when a fix for
+    // https://github.com/rust-lang/rust/issues/107466 is implemented.
+    assert!(res.is_ok());
+    // TODO: `a` should be dropped eagerly: https://github.com/rust-lang/rust/issues/107466
+    assert!(!a.get());
+    assert!(!b.get());
+    let res = std::panic::catch_unwind(move || {
+        drop(s);
+    });
+    assert_eq!(
+        *res.unwrap_err().downcast_ref::<&str>().unwrap(),
+        "first drop"
+    );
+    assert!(a.get());
     // Elements after the panicked element will leak.
-    assert!(!b);
+    assert!(!b.get());
 }

crossbeam-channel/tests/list.rs

@@ -1,6 +1,7 @@
 //! Tests for the list channel flavor.
 
 use std::any::Any;
+use std::cell::Cell;
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering;
 use std::thread;
@@ -580,3 +581,94 @@ fn channel_through_channel() {
     })
     .unwrap();
 }
+
+#[test]
+fn panic_on_drop() {
+    struct Msg1<'a>(&'a Cell<bool>);
+    impl Drop for Msg1<'_> {
+        fn drop(&mut self) {
+            if self.0.get() && !std::thread::panicking() {
+                panic!("double drop");
+            } else {
+                self.0.set(true);
+            }
+        }
+    }
+
+    struct Msg2<'a>(&'a Cell<bool>);
+    impl Drop for Msg2<'_> {
+        fn drop(&mut self) {
+            if self.0.get() {
+                panic!("double drop");
+            } else {
+                self.0.set(true);
+                panic!("first drop");
+            }
+        }
+    }
+
+    // normal (sender first)
+    let (s, r) = unbounded();
+    let (a, b) = (Cell::new(false), Cell::new(false));
+    s.send(Msg1(&a)).unwrap();
+    s.send(Msg1(&b)).unwrap();
+    drop(s);
+    assert!(!a.get());
+    assert!(!b.get());
+    drop(r);
+    assert!(a.get());
+    assert!(b.get());
+
+    // normal (receiver first)
+    let (s, r) = unbounded();
+    let (a, b) = (Cell::new(false), Cell::new(false));
+    s.send(Msg1(&a)).unwrap();
+    s.send(Msg1(&b)).unwrap();
+    drop(r);
+    // When the receiver is dropped, messages are dropped eagerly.
+    assert!(a.get());
+    assert!(b.get());
+    drop(s);
+    assert!(a.get());
+    assert!(b.get());
+
+    // panic on drop (sender first)
+    let (s, r) = unbounded();
+    let (a, b) = (Cell::new(false), Cell::new(false));
+    s.send(Msg2(&a)).unwrap();
+    s.send(Msg2(&b)).unwrap();
+    drop(s);
+    assert!(!a.get());
+    assert!(!b.get());
+    let res = std::panic::catch_unwind(move || {
+        drop(r);
+    });
+    assert_eq!(
+        *res.unwrap_err().downcast_ref::<&str>().unwrap(),
+        "first drop"
+    );
+    assert!(a.get());
+    // Elements after the panicked element will leak.
+    assert!(!b.get());
+
+    // panic on drop (receiver first)
+    let (s, r) = unbounded();
+    let (a, b) = (Cell::new(false), Cell::new(false));
+    s.send(Msg2(&a)).unwrap();
+    s.send(Msg2(&b)).unwrap();
+    let res = std::panic::catch_unwind(move || {
+        drop(r);
+    });
+    assert_eq!(
+        *res.unwrap_err().downcast_ref::<&str>().unwrap(),
+        "first drop"
+    );
+    // When the receiver is dropped, messages are dropped eagerly.
+    assert!(a.get());
+    // Elements after the panicked element will leak.
+    assert!(!b.get());
+    drop(s);
+    assert!(a.get());
+    // Elements after the panicked element will leak.
+    assert!(!b.get());
+}