title: How can I call a mutating method while holding a reference to self?
body: <p>I'm having a hard time with the borrow checker.</p>
  
  <pre><code>for item in self.xxx.iter() {
      self.modify_self_but_not_xxx(item);
  }
  </code></pre>
  
  <p>The above code worked <em>before</em> I refactored some code into <code>modify_self_but_not_xxx()</code>:</p>
  
  <pre class="lang-none prettyprint-override"><code>error: cannot borrow `*self` as mutable because `self.xxx` is also borrowed as immutable
  </code></pre>
  
  <p>How can I call a mutating method while holding a reference to <code>self</code> (e.g. from within a <code>for</code>-loop)?</p>