title: swift 3 error [_SwiftValue nsli_superitem]
body: <p>After swift 3 conversion I have been getting this error.</p>
  
  <blockquote>
    <p>'NSInvalidArgumentException', reason: '-[_SwiftValue nsli_superitem]: unrecognized selector sent to instance 0x600000a54820'</p>
  </blockquote>
  
  <p>The code in question is this, it use to work fine with swift 2:</p>
  
  <pre><code>let views = ["newView": userLabel]
  let widthConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[newView(0)]", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views)
  userMainLabel.addConstraints(widthConstraints)
  </code></pre>