anchor.diff:          backgroundImage: backgroundImage != null ? new BackgroundImage(
             image: backgroundImage
           ) : null,
  -        shape: BoxShape.circle
  +        shape: BoxShape.circle,
         ),
  -      child: new Center(
  +      child: child != null ? new Center(
           child: new DefaultTextStyle(
             style: theme.primaryTextTheme.title,
  -          child: child
  +          child: child,
           )
  -      )
  +      ) : null,
       );
     }
   }
  
positive.code: 
  /// A circle that represents a user.
  ///
  /// Typicially used with a user's profile image, or, in the absence of
  /// such an image, the user's initials. A given user's initials should
  /// always be paired with the same background color, for consistency.
  ///
  /// See also:
  ///
  ///  * [Chip]
  ///  * [ListItem]
  ///  * <https://material.google.com/components/chips.html#chips-contact-chips>
  class CircleAvatar extends StatelessWidget {
    /// Creates a circle that represents a user.
  
negative.code:   }) : super(key: key);
  
    /// The widget below this widget in the tree.
    ///
    /// Typically a [Text] widget. If the [CircleAvatar] is to have an image, use
    /// [backgroundImage] instead.
    final Widget child;
  
    /// The color with which to fill the circle. Changing the background
  