comments from @lzutao

src/liballoc/tests/str.rs

@@ -1109,7 +1109,7 @@ fn test_iterator_last() {
 }
 
 #[test]
-fn test_chars_display() {
+fn test_chars_debug() {
     let s = "ศไทย中华Việt Nam";
     let c = s.chars();
     assert_eq!(

src/libcore/str/mod.rs

@@ -601,7 +601,7 @@ fn last(mut self) -> Option<char> {
 }
 
 #[stable(feature = "chars_debug_impl", since = "1.38.0")]
-impl<'a> fmt::Debug for Chars<'a> {
+impl fmt::Debug for Chars<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "Chars(")?;
         f.debug_list().entries(self.clone()).finish()?;