title: Cannot assign value of type 'String??' to type 'String?' error
body: <p>let say I defined a class</p>
  <pre><code>class Dummy {
  
      var title: String?
  }
  </code></pre>
  <p>and I have a dictionary as</p>
  <pre><code>let foo: [Int: String?]  = [:]
  </code></pre>
  <p>then when I make an assignment as below</p>
  <pre><code>var dummy = Dummy()
  
  dummy.title = foo[1]
  </code></pre>
  <p>it says</p>
  <blockquote>
  <p>Cannot assign value of type 'String??' to type 'String?'</p>
  <p>Insert ' as! String'</p>
  </blockquote>
  <p>return type of <code>foo</code> is <code>String?</code> and <code>Dictionary</code> returns optional of its value type when used subscript but what is <code>String??</code> type in swift?</p>
  <p>I think it should be legal to make such assignment.
  Why it complains and how should I make this assignment</p>