anchor.diff:    /**
      * The unique instance of this class.
      */
  -  static DynamicTypeImpl _INSTANCE = new DynamicTypeImpl._();
  -
  -  /**
  -   * Return the unique instance of this class.
  -   */
  -  static DynamicTypeImpl get instance => _INSTANCE;
  +  static final DynamicTypeImpl instance = new DynamicTypeImpl._();
   
     /**
      * Prevent the creation of instances of this class.
  
positive.code:   /**
     * The unique instance of this class.
     */
    static UndefinedTypeImpl _INSTANCE = new UndefinedTypeImpl._();
  
    /**
     * Return the unique instance of this class.
     */
    static UndefinedTypeImpl get instance => _INSTANCE;
  
    /**
     * Prevent the creation of instances of this class.
  
negative.code:   /**
     * The unique instance of this class.
     */
    static final BottomTypeImpl instance = new BottomTypeImpl._();
  
    /**
     * Prevent the creation of instances of this class.
  