title: Type 'String.Index' does not conform protocol '_Strideable'
body: <p>I read <a href="https://stackoverflow.com/questions/24880604/type-string-index-does-not-conform-protocol-integerliteralconvertible">this</a> thread but it seems have another problem. This code:</p>
  
  <pre><code>if value.range(of: String(formatter.minusSign))?.count &gt; 0 {
      //STH
  }
  </code></pre>
  
  <p>(where <code>formatter</code> is <code>NumberFormatter</code> object and <code>value</code> is <code>String</code>) produce this error in Swift:</p>
  
  <blockquote>
    <p>Type 'String.Index' does not conform to protocol '_Strideable'</p>
  </blockquote>
  
  <p>How to solve it?</p>