title: Pattern matching equal null vs is null
body: <p>From Microsoft new-features-in-c-7-0:</p>
  
  <pre><code>public void PrintStars(object o)
  {
      if (o is null) return;     // constant pattern "null"
      if (!(o is int i)) return; // type pattern "int i"
      WriteLine(new string('*', i));
  }
  </code></pre>
  
  <p>Whats the diferrence of <code>o == null</code> and <code>o is null</code>?</p>