title: Swift 2 unused constant warning
body: <p>I am getting a warning saying my constant is unused:</p>
  
  <blockquote>
    <p>Initialization of immutable value 'myConst' was never used; consider replacing with assignment to '_' or removing it</p>
  </blockquote>
  
  <pre><code>if someVal["value"] != nil {
      let myConst = someVal["value"]
  }
  </code></pre>
  
  <p>So what will renaming <code>let myConst = someVal["value"]</code> into <code>_ myConst = someVal["value"]</code> do/mean?</p>