2 files changed, 38 insertions, 0 deletions
diff --git a/library/alloc/tests/lib.rs b/library/alloc/tests/lib.rs
index ffc9a233b66..1d07a7690da 100644
--- a/library/alloc/tests/lib.rs
+++ b/library/alloc/tests/lib.rs
@@ -28,6 +28,7 @@
 #![feature(iter_next_chunk)]
 #![feature(round_char_boundary)]
 #![feature(slice_partition_dedup)]
+#![feature(string_from_utf8_lossy_owned)]
 #![feature(string_remove_matches)]
 #![feature(const_btree_len)]
 #![feature(const_trait_impl)]
diff --git a/library/alloc/tests/string.rs b/library/alloc/tests/string.rs
index dc03c4860e8..d996c55f946 100644
--- a/library/alloc/tests/string.rs
+++ b/library/alloc/tests/string.rs
@@ -115,6 +115,43 @@ fn test_from_utf8_lossy() {
 }
 
 #[test]
+fn test_fromutf8error_into_lossy() {
+    fn func(input: &[u8]) -> String {
+        String::from_utf8(input.to_owned()).unwrap_or_else(|e| e.into_utf8_lossy())
+    }
+
+    let xs = b"hello";
+    let ys = "hello".to_owned();
+    assert_eq!(func(xs), ys);
+
+    let xs = "ศไทย中华Việt Nam".as_bytes();
+    let ys = "ศไทย中华Việt Nam".to_owned();
+    assert_eq!(func(xs), ys);
+
+    let xs = b"Hello\xC2 There\xFF Goodbye";
+    assert_eq!(func(xs), "Hello\u{FFFD} There\u{FFFD} Goodbye".to_owned());
+
+    let xs = b"Hello\xC0\x80 There\xE6\x83 Goodbye";
+    assert_eq!(func(xs), "Hello\u{FFFD}\u{FFFD} There\u{FFFD} Goodbye".to_owned());
+
+    let xs = b"\xF5foo\xF5\x80bar";
+    assert_eq!(func(xs), "\u{FFFD}foo\u{FFFD}\u{FFFD}bar".to_owned());
+
+    let xs = b"\xF1foo\xF1\x80bar\xF1\x80\x80baz";
+    assert_eq!(func(xs), "\u{FFFD}foo\u{FFFD}bar\u{FFFD}baz".to_owned());
+
+    let xs = b"\xF4foo\xF4\x80bar\xF4\xBFbaz";
+    assert_eq!(func(xs), "\u{FFFD}foo\u{FFFD}bar\u{FFFD}\u{FFFD}baz".to_owned());
+
+    let xs = b"\xF0\x80\x80\x80foo\xF0\x90\x80\x80bar";
+    assert_eq!(func(xs), "\u{FFFD}\u{FFFD}\u{FFFD}\u{FFFD}foo\u{10000}bar".to_owned());
+
+    // surrogates
+    let xs = b"\xED\xA0\x80foo\xED\xBF\xBFbar";
+    assert_eq!(func(xs), "\u{FFFD}\u{FFFD}\u{FFFD}foo\u{FFFD}\u{FFFD}\u{FFFD}bar".to_owned());
+}
+
+#[test]
 fn test_from_utf16() {
     let pairs = [
         (