title: Why does this Flutter example not have a return keyword?
body: <p>I am reading over the documentation for Flutter.</p>
  
  <p>On <a href="https://api.flutter.dev/flutter/widgets/State/setState.html" rel="nofollow noreferrer">this page</a>, I have observed the following curious method. In the method, the declared return type is Future. The method though, does not have the return keyword present anywhere. Why is this?</p>
  
  <pre><code>Future&lt;void&gt; _incrementCounter() async {
    setState(() {
      _counter++;
    });
    Directory directory = await getApplicationDocumentsDirectory();
    final String dirName = directory.path;
    await File('$dir/counter.txt').writeAsString('$_counter');
  }
  </code></pre>
  
  <p>I have been able to ascertain that all flutter functions return a value, and the default return value is null. But if this method always returns null, then why declare a return type of <code>Future&lt;void&gt;</code>?</p>