title: PropType is defined but prop is never used
body: <p>Why am i getting the lint errors <code>PropType is defined but prop is never used</code> for all props in the sample code below:</p>
  
  <pre><code>const propTypes = {
    prop1: PropTypes.string,
    prop2: PropTypes.string,
    prop3: PropTypes.number,
    prop4: PropTypes.string,
    prop5: PropTypes.number,
  };
  
  const userDetails = (props) =&gt; ((props.props2 &gt; 0 &amp; props.prop1 === props.props3) ?
    t('translation/abc')
    : t('translation/def'));
  
  const userDetails2 = (props) =&gt; ((props.props1 &gt; 0 &amp; props.prop4 === props.props5) ?
    t('translation/ted')
    : t('translation/sted'));
  </code></pre>