title: iOS 9 constraint error
body: <p>This code:</p>
  
  <pre><code>[self.collectionView setTranslatesAutoresizingMaskIntoConstraints: NO];
  
  [self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.collectionView
                                                        attribute:NSLayoutAttributeTop
                                                        relatedBy:NSLayoutRelationEqual
                                                           toItem:self.topLayoutGuide
                                                        attribute:NSLayoutAttributeTop
                                                       multiplier:1.0f
                                                         constant:1.0f]];
  
  [self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.collectionView
                                                        attribute:NSLayoutAttributeBottom
                                                        relatedBy:NSLayoutRelationEqual
                                                           toItem:self.bottomLayoutGuide
                                                        attribute:NSLayoutAttributeBottom
                                                       multiplier:1.0f 
                                                         constant:0.f]];
  
  [self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.collectionView 
                                                        attribute:NSLayoutAttributeLeading 
                                                        relatedBy:NSLayoutRelationEqual 
                                                           toItem:self.view
                                                        attribute:NSLayoutAttributeLeading
                                                       multiplier:1.0f
                                                         constant:0.0f]];
  
  [self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.collectionView
                                                        attribute:NSLayoutAttributeTrailing 
                                                        relatedBy:NSLayoutRelationEqual 
                                                           toItem:self.view
                                                        attribute:NSLayoutAttributeRight
                                                       multiplier:1.0f 
                                                         constant:0.0f]];
  </code></pre>
  
  <p>Work's fine on iOS 8 and iOS7 but now when with iOS9 when I run my app I get this error : </p>
  
  <blockquote>
    <p>Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[NSLayoutConstraint constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:]: A constraint cannot be made between a leading/trailing attribute and a right/left attribute. Use leading/trailing for both or neither.'</p>
  </blockquote>
  
  <p>When I remove those constraints my app works fine. So I need to know what's the problem and what have been changed from iOS8 to iOS9.</p>