title: Subscript array of structs
body: <p>Given I have array of stucts like this:</p>
  
  <p><code>let array = [Struct(key: "a", value: 1), Struct(key: "b", value:2)]</code></p>
  
  <p>How can I subscript the array with the key? </p>
  
  <p><code>array["b"]</code> would be nice, but as expected, it doesn't work.</p>
  
  <p><em>Edit:</em> The reason I'm not using dictionary, is I need to preserve the order of items.</p>