From 5717d99d1b3b76ec7814c95dfcc0399ab4ddaa83 Mon Sep 17 00:00:00 2001
From: Simon Sapin <simon.sapin@exyr.org>
Date: Fri, 6 Jul 2018 19:30:09 +0200
Subject: [PATCH] Add some unit tests for dangling Weak references

---
 src/liballoc/tests/arc.rs | 55 +++++++++++++++++++++++++++++++++++++++
 src/liballoc/tests/lib.rs |  2 ++
 src/liballoc/tests/rc.rs  | 55 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 112 insertions(+)
 create mode 100644 src/liballoc/tests/arc.rs
 create mode 100644 src/liballoc/tests/rc.rs

diff --git a/src/liballoc/tests/arc.rs b/src/liballoc/tests/arc.rs
new file mode 100644
index 00000000000..753873dd294
--- /dev/null
+++ b/src/liballoc/tests/arc.rs
@@ -0,0 +1,55 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::any::Any;
+use std::sync::{Arc, Weak};
+
+#[test]
+fn uninhabited() {
+    enum Void {}
+    let mut a = Weak::<Void>::new();
+    a = a.clone();
+    assert!(a.upgrade().is_none());
+
+    let mut a: Weak<Any> = a;  // Unsizing
+    a = a.clone();
+    assert!(a.upgrade().is_none());
+}
+
+#[test]
+fn slice() {
+    let a: Arc<[u32; 3]> = Arc::new([3, 2, 1]);
+    let a: Arc<[u32]> = a;  // Unsizing
+    let b: Arc<[u32]> = Arc::from(&[3, 2, 1][..]);  // Conversion
+    assert_eq!(a, b);
+
+    // Exercise is_dangling() with a DST
+    let mut a = Arc::downgrade(&a);
+    a = a.clone();
+    assert!(a.upgrade().is_some());
+}
+
+#[test]
+fn trait_object() {
+    let a: Arc<u32> = Arc::new(4);
+    let a: Arc<Any> = a;  // Unsizing
+
+    // Exercise is_dangling() with a DST
+    let mut a = Arc::downgrade(&a);
+    a = a.clone();
+    assert!(a.upgrade().is_some());
+
+    let mut b = Weak::<u32>::new();
+    b = b.clone();
+    assert!(b.upgrade().is_none());
+    let mut b: Weak<Any> = b;  // Unsizing
+    b = b.clone();
+    assert!(b.upgrade().is_none());
+}
diff --git a/src/liballoc/tests/lib.rs b/src/liballoc/tests/lib.rs
index dbac2c0bb18..2c361598e89 100644
--- a/src/liballoc/tests/lib.rs
+++ b/src/liballoc/tests/lib.rs
@@ -32,12 +32,14 @@ extern crate rand;
 use std::hash::{Hash, Hasher};
 use std::collections::hash_map::DefaultHasher;
 
+mod arc;
 mod binary_heap;
 mod btree;
 mod cow_str;
 mod fmt;
 mod heap;
 mod linked_list;
+mod rc;
 mod slice;
 mod str;
 mod string;
diff --git a/src/liballoc/tests/rc.rs b/src/liballoc/tests/rc.rs
new file mode 100644
index 00000000000..baa0406acfc
--- /dev/null
+++ b/src/liballoc/tests/rc.rs
@@ -0,0 +1,55 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::any::Any;
+use std::rc::{Rc, Weak};
+
+#[test]
+fn uninhabited() {
+    enum Void {}
+    let mut a = Weak::<Void>::new();
+    a = a.clone();
+    assert!(a.upgrade().is_none());
+
+    let mut a: Weak<Any> = a;  // Unsizing
+    a = a.clone();
+    assert!(a.upgrade().is_none());
+}
+
+#[test]
+fn slice() {
+    let a: Rc<[u32; 3]> = Rc::new([3, 2, 1]);
+    let a: Rc<[u32]> = a;  // Unsizing
+    let b: Rc<[u32]> = Rc::from(&[3, 2, 1][..]);  // Conversion
+    assert_eq!(a, b);
+
+    // Exercise is_dangling() with a DST
+    let mut a = Rc::downgrade(&a);
+    a = a.clone();
+    assert!(a.upgrade().is_some());
+}
+
+#[test]
+fn trait_object() {
+    let a: Rc<u32> = Rc::new(4);
+    let a: Rc<Any> = a;  // Unsizing
+
+    // Exercise is_dangling() with a DST
+    let mut a = Rc::downgrade(&a);
+    a = a.clone();
+    assert!(a.upgrade().is_some());
+
+    let mut b = Weak::<u32>::new();
+    b = b.clone();
+    assert!(b.upgrade().is_none());
+    let mut b: Weak<Any> = b;  // Unsizing
+    b = b.clone();
+    assert!(b.upgrade().is_none());
+}