anchor.diff:    bool operator ==(dynamic other) {
       if (identical(this, other))
         return true;
  -    if (other is! Border)
  +    if (other.runtimeType != runtimeType)
         return false;
       final Border typedOther = other;
       return top == typedOther.top &&
  
positive.code:   }
  
    void _paintBorderWithRadius(Canvas canvas, Rect rect) {
      assert(_hasUniformBorder);
      assert(_decoration.shape == BoxShape.rectangle);
      Color color = _decoration.border.top.color;
      double width = _decoration.border.top.width;
  
negative.code:     return new EdgeInsets.TRBL(top.width, right.width, bottom.width, left.width);
    }
  
    /// Whether all four sides of the border are identical.
    bool get isUniform {
      assert(top != null);
      assert(right != null);
      assert(bottom != null);
      assert(left != null);
  
      final Color topColor = top.color;
      if (right.color != topColor ||
          bottom.color != topColor ||
          left.color != topColor)
        return false;
  
      final double topWidth = top.width;
      if (right.width != topWidth ||
          bottom.width != topWidth ||
          left.width != topWidth)
        return false;
  
      return true;
    }
  
    /// Creates a new border with the widths of this border multiplied by [t].
    Border scale(double t) {
      return new Border(
        top: top.copyWith(width: t * top.width),
  