title: Why can a struct holding a Box<T> not be copied?
body: <p>An article that I read recently stated that a struct that holds a <code>Box&lt;T&gt;</code> as a field is not <code>Copy</code>.</p>
  
  <p>This confuses me, since I thought that any type whose size is known can be stored on the stack - and is therefore <code>Copy</code>.</p>
  
  <p>Isn't the <code>Box</code>'s size always the same? I thought that it was just a reference to a heap allocated memory - and does therefore have always the same size.</p>