title: binary operator '/' cannot be applied to two 'Double' operands
body: <p>While trying to execute this block of code in Swift 3, I encountered the error: binary operator '/' cannot be applied to two 'Double' operands</p>
  
  <pre><code>var array2 = [8, 7, 19, 20]
  
  for (index, value) in array2.enumerated() {
      array2[index] = Double(value) / 2.0
  }
  </code></pre>
  
  <p>Yet this works</p>
  
  <pre><code>var array2 = [Double]()
  array2 = [8, 7, 19, 20]
  
  for (index, value) in array2.enumerated() {
      array2[index] = value / 2.0
  }
  </code></pre>
  
  <p>Why doesn't the first block of code work?</p>