From 1f6f917f73a4372f098e9b19560b5945be145dc3 Mon Sep 17 00:00:00 2001
From: Giacomo Stevanato <giaco.stevanato@gmail.com>
Date: Thu, 29 Oct 2020 11:48:56 +0100
Subject: [PATCH] Added test for issue #78498

---
 library/alloc/tests/string.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/library/alloc/tests/string.rs b/library/alloc/tests/string.rs
index a6e41b21b61..b28694186b6 100644
--- a/library/alloc/tests/string.rs
+++ b/library/alloc/tests/string.rs
@@ -1,6 +1,7 @@
 use std::borrow::Cow;
 use std::collections::TryReserveError::*;
 use std::ops::Bound::*;
+use std::panic;
 
 pub trait IntoCow<'a, B: ?Sized>
 where
@@ -378,6 +379,20 @@ fn test_retain() {
 
     s.retain(|_| false);
     assert_eq!(s, "");
+
+    let mut s = String::from("0è0");
+    let _ = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        let mut count = 0;
+        s.retain(|_| {
+            count += 1;
+            match count {
+                1 => false,
+                2 => true,
+                _ => panic!(),
+            }
+        });
+    }));
+    assert!(std::str::from_utf8(s.as_bytes()).is_ok());
 }
 
 #[test]