title: for-in statement
body: <p>TypeScript docs say nothing about loop like <code>for</code> or <code>for-in</code>. From playing with the language it seems that only <code>any</code> or <code>string</code> variables are supported in <code>for</code> loop.</p>
  
  <p>Why has this decision been made?</p>
  
  <p>Why not use the type information and have strongly-typed iteration variable?</p>