title: named parameter in Dart
body: <p>Good day, I am trying to apply named parameter {num phone} to the below example:</p>
  <pre><code>main(){
  
  showInfo(&quot;abc@mail.com&quot;, &quot;Fatima&quot;);
  }
  
  String showInfo(String email, String name, {num phone}) {
  print(email);
  print(name);
  print(phone);
  return &quot;$email : $name : $phone&quot;;
  } 
  </code></pre>
  <p>but I receive the error:</p>
  <pre><code>Error: The parameter 'phone' can't have a value of 'null' because of its type 'num', but the implicit 
  default value is 'null'.
  Try adding either an explicit non-'null' default value or the 'required' modifier.
  Future&lt;String&gt; showInfo(String email, String name, {num phone}) async {
                                                       ^^^^^
  </code></pre>
  <p>your help is appreciated.</p>