From 591584e71f7d8a613d586066c8b01c1eecf08f35 Mon Sep 17 00:00:00 2001
From: Mikail Bagishov <bagishov.mikail@yandex.ru>
Date: Tue, 26 May 2020 23:48:36 +0300
Subject: [PATCH 1/2] Add tests for 'impl Default for [T; N]'

---
 src/libcore/tests/array.rs | 41 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/src/libcore/tests/array.rs b/src/libcore/tests/array.rs
index c2a816f0a7d90..41855a9a8cbab 100644
--- a/src/libcore/tests/array.rs
+++ b/src/libcore/tests/array.rs
@@ -241,3 +241,44 @@ fn iterator_drops() {
     }
     assert_eq!(i.get(), 5);
 }
+
+#[test]
+fn array_default_impl_avoids_leaks_on_panic() {
+    use core::sync::atomic::{AtomicUsize, Ordering::Relaxed};
+    static COUNTER: AtomicUsize = AtomicUsize::new(0);
+    #[derive(Debug)]
+    struct Bomb(usize);
+
+    impl Default for Bomb {
+        fn default() -> Bomb {
+            if COUNTER.load(Relaxed) == 3 {
+                panic!("bomb limit exceeded");
+            }
+
+            COUNTER.fetch_add(1, Relaxed);
+            Bomb(COUNTER.load(Relaxed))
+        }
+    }
+
+    impl Drop for Bomb {
+        fn drop(&mut self) {
+            COUNTER.fetch_sub(1, Relaxed);
+        }
+    }
+
+    let res = std::panic::catch_unwind(|| <[Bomb; 5]>::default());
+    let panic_msg = match res {
+        Ok(_) => unreachable!(),
+        Err(p) => p.downcast::<&'static str>().unwrap(),
+    };
+    assert_eq!(*panic_msg, "bomb limit exceeded");
+    // check that all bombs are successfully dropped
+    assert_eq!(COUNTER.load(Relaxed), 0);
+}
+
+#[test]
+fn empty_array_is_always_default() {
+    struct DoesNotImplDefault;
+
+    let _arr = <[DoesNotImplDefault; 0]>::default();
+}

From 3313bf62ac45fab2c39e49c788423153754087a9 Mon Sep 17 00:00:00 2001
From: Mikail Bagishov <bagishov.mikail@yandex.ru>
Date: Thu, 28 May 2020 20:45:21 +0300
Subject: [PATCH 2/2] Skip leak test on targets without panic=unwind

---
 src/libcore/tests/array.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/libcore/tests/array.rs b/src/libcore/tests/array.rs
index 41855a9a8cbab..4bc44e98fc802 100644
--- a/src/libcore/tests/array.rs
+++ b/src/libcore/tests/array.rs
@@ -242,7 +242,14 @@ fn iterator_drops() {
     assert_eq!(i.get(), 5);
 }
 
+// This test does not work on targets without panic=unwind support.
+// To work around this problem, test is marked is should_panic, so it will
+// be automagically skipped on unsuitable targets, such as
+// wasm32-unknown-unkown.
+//
+// It means that we use panic for indicating success.
 #[test]
+#[should_panic(expected = "test succeeded")]
 fn array_default_impl_avoids_leaks_on_panic() {
     use core::sync::atomic::{AtomicUsize, Ordering::Relaxed};
     static COUNTER: AtomicUsize = AtomicUsize::new(0);
@@ -274,6 +281,7 @@ fn array_default_impl_avoids_leaks_on_panic() {
     assert_eq!(*panic_msg, "bomb limit exceeded");
     // check that all bombs are successfully dropped
     assert_eq!(COUNTER.load(Relaxed), 0);
+    panic!("test succeeded")
 }
 
 #[test]