+ ;; when ses-rename-cell is called interactively, then 'sym' is the
+ ;; 'cursor-intangible' property of text at cursor position, while
+ ;; 'old-name' is the symbol stored in array cell at coordinate
+ ;; 'rowcol' corresponding to 'ses-cell' property of symbol
+ ;; 'sym'. Both must be the same.
+ (unless (eq sym old-name)
+ (error "Spreadsheet is broken, both symbols %S and %S refering to cell (%d,%d)" sym old-name row col))