Cannot convert value of type Substring to expected argument type String - Swift 4 : <p>Trying to get substring of String and append it to array of Strings:</p>

<pre><code>var stringToSplit = "TEST TEXT"
var s = [String]()
let subStr = anotherString[0 ..&lt; 6]
s.append(subStr) // &lt;---- HERE I GET THE ERROR
</code></pre>

<p><a href="https://i.stack.imgur.com/9Ijkp.png" rel="noreferrer"><img src="https://i.stack.imgur.com/9Ijkp.png" alt="error desc"></a></p>
