test: add failing test for #2022

Signed-off-by: Yaroslav Bolyukin <iam@lach.pw>

tests/opts.rs

@@ -510,3 +510,12 @@ fn long_eq_val_starts_with_eq() {
 
     assert_eq!("=value", matches.value_of("opt").unwrap());
 }
+
+#[test]
+fn issue_2022_get_flags_misuse() {
+    let app = App::new("test")
+        .help_heading("test")
+        .arg(Arg::new("a").long("a").default_value("32"));
+    let matches = app.get_matches_from(&[""]);
+    assert!(matches.value_of("a").is_some())
+}