Do not confuse defined names and cell refs

CALCULATION_REGEXP_CELLREF is not sufficiently robust.
It treats some perfectly legal defined names, e.g. A1A, as cell refs.
When the Xlsx Writer tries to save a worksheet which uses such a name
in a formula in a cell, it throws an exception.

The new DefinedNameConfusedForCellTest is a simple demonstration.
The Regexp has been changed to ensure the name starts on a Word boundary,
and to make sure it is not followed by a word character or period.
This fixes the problem, and does not appear to cause any regression
problems in the test suite.

Closes #1263

Author: oleibman

src/PhpSpreadsheet/Calculation/Calculation.php

@@ -25,7 +25,7 @@ class Calculation
     //    Function (allow for the old @ symbol that could be used to prefix a function, but we'll ignore it)
     const CALCULATION_REGEXP_FUNCTION = '@?(?:_xlfn\.)?([A-Z][A-Z0-9\.]*)[\s]*\(';
     //    Cell reference (cell or range of cells, with or without a sheet reference)
-    const CALCULATION_REGEXP_CELLREF = '((([^\s,!&%^\/\*\+<>=-]*)|(\'[^\']*\')|(\"[^\"]*\"))!)?\$?([a-z]{1,3})\$?(\d{1,7})';
+    const CALCULATION_REGEXP_CELLREF = '((([^\s,!&%^\/\*\+<>=-]*)|(\'[^\']*\')|(\"[^\"]*\"))!)?\$?\b([a-z]{1,3})\$?(\d{1,7})(?![\w.])';
     //    Named Range of cells
     const CALCULATION_REGEXP_NAMEDRANGE = '((([^\s,!&%^\/\*\+<>=-]*)|(\'[^\']*\')|(\"[^\"]*\"))!)?([_A-Z][_A-Z0-9\.]*)';
     //    Error

tests/PhpSpreadsheetTests/Calculation/DefinedNameConfusedForCellTest.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Calculation;
+
+use PhpOffice\PhpSpreadsheet\Shared\File;
+use PHPUnit\Framework\TestCase;
+
+class DefinedNameConfusedForCellTest extends TestCase
+{
+    public function testDefinedName()
+    {
+        $obj = new \PhpOffice\PhpSpreadsheet\Spreadsheet();
+        $sheet0 = $obj->setActiveSheetIndex(0);
+        $sheet0->setCellValue('A1', 2);
+        $obj->addNamedRange(new \PhpOffice\PhpSpreadsheet\NamedRange('A1A', $sheet0, 'A1'));
+        $sheet0->setCellValue('B1', '=2*A1A');
+        $writer = \PhpOffice\PhpSpreadsheet\IOFactory::createWriter($obj, 'Xlsx');
+        $filename = tempnam(File::sysGetTempDir(), 'phpspreadsheet-test');
+        $writer->save($filename);
+        self::assertTrue(true);
+    }
+}