Invalid cell coordinate range causes infinite loop

[rdarcy1]

This is:

- [x] a bug report
- [ ] a feature request

What is the expected behavior?

An exception should be thrown for an invalid range, or maybe just the start cell should be returned.

What is the current behavior?

The program gets stuck in a loop and PHP runs out of memory.

I think the offending loop is \PhpOffice\PhpSpreadsheet\Cell\Coordinate line 372

while ($currentCol != $endCol) {
    ...
}

Probably needs a magnitude comparison rather than a straight equality comparison, since if an invalid range is given the current column will never equal the end column.

What are the steps to reproduce?

Please provide a Minimal, Complete, and Verifiable example of code that exhibits the issue without relying on an external Excel file or a web server:

<?php

require __DIR__ . '/vendor/autoload.php';

// Gets stuck in a loop
\PhpOffice\PhpSpreadsheet\Cell\Coordinate::extractAllCellReferencesInRange('Z1:A1');


// Which means the following gets stuck, causing a hard to debug memory error for
// code that isn't necessarily obviously wrong.
$spreadsheet = new \PhpOffice\PhpSpreadsheet\Spreadsheet();
$spreadsheet->getActiveSheet()
    ->mergeCellsByColumnAndRow(0, 1, 1, 1);

Which versions of PhpSpreadsheet and PHP are affected?

PhpSpreadsheet 1.2