This PR will probably remain in draft status for some time. It needs updates, and I need more time to understand exactly what it is doing. It is a replacement for PR PHPOffice#2096, intended as a fix for issue PHPOffice#1449. That PR has been stuck, with a good deal of acrimony, for over 2 years. In the interim, all the parameters for the functions involved were renamed, the functions were refactored to have fewer parameters with new class properties replacing the missing parameters, special code was added for absolute references, and code was refactored putting some of the methods involved in a new class under a new method name. In addition, the original PR was not Php8-compliant (one of the sticking points regarding implementing it), and there were a great many formatting problems (another sticking point). This has made it very difficult to figure out exactly what was intended in the original PR.

This PR (a) addresses some of the issues associated with the original issue (deleting columns/rows at the end of a range passed to a formula *on the same sheet*), and (b) does not cause any existing tests to fail. Many more unit tests are needed (another sticking point); in particular, there are changes involving data validations, comments, defined names, and other elements which are not adequately tested.

Aside from those, PhpSpreadsheet does not adjust formulas on a different sheet which involve deleted rows/columns, and it should, as Excel does.

Similarly, it appears that Excel doesn't do anything extraordinary when the right/bottom part of the range is deleted, but when the left/top part is deleted, it converts the range to #REF! at least some of the time. This needs more research; if confirmed, it needs to be added to PhpSpreadsheet.

Correctly identified an unneeded statement.