anchor.diff:      this.fixedLeftColumns = 0,
       this.lmRatio = 1.2,
       required super.rows,
  -  }) {
  +  })  : assert(fixedLeftColumns >= 0),
  +        assert(fixedTopRows >= 0) {
       if (scrollController != null) {
         _coreVerticalController = scrollController!;
       } else {
  
positive.code:         theme,
          tableColumnWidths.length - fixedLeftColumns,
          defaultRowColor,
          fixedTopRows);
  
      List<TableRow>? fixedTopRowsRows = fixedTopRows > 0
          ? (fixedTopRows == 1
              ? [
                  _buildHeadingRow(context, theme, effectiveHeadingRowColor,
  
negative.code:                     (rows[rowIndex] as DataRow2).specificRowHeight != null)
                  ? (rows[rowIndex] as DataRow2).specificRowHeight!
                  : defaultDataRowHeight);
  
          if (fixedCornerRows != null && rowIndex < fixedCornerRows.length - 1) {
            fixedCornerRows[rowIndex].children![0] = x;
          } else if (fixedColumnRows != null) {
            fixedColumnRows[rowIndex - skipRows].children![0] = x;
          } else if (fixedRows != null && rowIndex < fixedRows.length - 1) {
            fixedRows[rowIndex].children![0] = x;
          } else {
            coreRows[rowIndex - skipRows].children![0] = x;
          }
  
          rowIndex += 1;
        }
      }
  