title: Assignment in ternary conditional operator produces "Expression is not assignable" error
body: <p>Can anybody tell me why the following was okay:</p>
  
  <pre><code>if (newEditingMode) {
      dayView.dayViewIsInEditingMode = YES;
  }
  else{
      dayView.dayViewIsInEditingMode = NO;
  }
  </code></pre>
  
  <p>But the following gave the error <code>Expression is not assignable</code>:</p>
  
  <pre><code>newEditingMode ? dayView.dayViewIsInEditingMode = YES : dayView.dayViewIsInEditingMode = NO;
  </code></pre>