title: Sass BEM: avoid modifier duplication when element is inside a modifier
body: <p>Can I somehow refactor the following code snippet to get rid of <strong>double modifier declaration</strong>?</p>
  
  <pre><code>.block {
    &amp;__element {
      rule: value;
    }
    &amp;--modifier {
      rule: value;
    }
    &amp;--modifier &amp; {
      &amp;__element {
        rule: value;
      }
    }
  }
  </code></pre>
  
  <p>Output wanted:</p>
  
  <pre><code>.block {
     property: value;
  }
  .block--modifier {
    property: value;
  }
  .block--modifier .block__element {
    property: value;
  }
  </code></pre>