Add test of Display for TokenStream

Author: dtolnay

tests/test.rs

@@ -718,6 +718,13 @@ fn test_debug_ident() {
     assert_eq!(expected, format!("{:?}", ident));
 }
 
+#[test]
+fn test_display_tokenstream() {
+    let tts = TokenStream::from_str("[a + 1]").unwrap();
+    assert_eq!(format!("{tts}"), "[a + 1]");
+    assert_eq!(format!("{tts:-^5}"), "[--a-- --+-- --1--]"); // FIXME
+}
+
 #[test]
 fn test_debug_tokenstream() {
     let tts = TokenStream::from_str("[a + 1]").unwrap();