title: Redefinition of typedef is a C11 feature
body: <p>I'm trying to create a header file as such:</p>
  
  <pre><code>#import &lt;UIKit/UIKit.h&gt;
  
  typedef void (^RevealBlock)();
  
  @interface BFTasksViewController : UITableViewController &lt;UITableViewDataSource, UITableViewDelegate&gt; {
  @private
      RevealBlock _revealBlock;
  }
  
  - (id)initWithTitle:(NSString *)title withRevealBlock:(RevealBlock)revealBlock;
  
  @end
  </code></pre>
  
  <p>But I get this warning: </p>
  
  <blockquote>
    <p>Redefinition of typedef 'RevealBlock' is a C11 feature</p>
  </blockquote>
  
  <p>Is this something to be worried about? I'm looking at the <a href="https://github.com/gresrun/GHSidebarNav" rel="noreferrer">GHSidebarNav project</a>, which seems to use it just fine. </p>