title: How to exclude properties from interface while inheriting
body: <p>I've two interfaces, <code>X</code> and <code>Y</code>. <code>X</code> has 2 properties, <code>x1</code> and <code>x2</code>. Now <code>Y</code> wants to inherit from <code>X</code> but don't want <code>x2</code> to be inherited. </p>
  
  <pre><code>interface X {
    x1 : string;
    x2 : string;
  }
  
  interface Y extends X{
    // x2 shouldn't be available here
  }
  </code></pre>
  
  <p>As am new in <code>TypeScript</code>, I can't figure it out. Is there any <code>extends X without x1</code> type built-in feature available in <code>TypeScript</code> ? </p>
  
  <p>NOTE: In my real case, <code>X</code> is a built-in <code>interface</code>. So, I need to do this without changing the <code>X</code> interface. Is it possible ?</p>