title: Why a final field should be initialised when it is made nullable?
body: <pre class="lang-dart prettyprint-override"><code>class A {
    final int? b; // Error
  }
  </code></pre>
  <p>Error:</p>
  <blockquote>
  <p>The final variable 'b' must be initialized.</p>
  </blockquote>
  <p>Since the field <code>b</code> is nullable, it could be left uninitialised and hence needs no initialisation work. But it gives an error.</p>