POWER Needs to Accept NULL Args

Investigating issue #1622, I found that its extremely complicated formula, which had been leading to an incorrect result, now led to an exception. I am able to fix the exception; unfortunately, I am no closer to resolving the original issue. So I'll apply the baby step while continuing to investigate. Function POWER had changed from untyped args to a defined set of types. The set of types was determined according to the doc block, but that was incomplete - it had neglected to include `null` and `bool`. This PR corrects the function prototype and the doc block, and adds the missing tests for those conditions.

Author: oleibman

src/PhpSpreadsheet/Calculation/MathTrig/Operations.php

@@ -52,14 +52,14 @@ public static function mod(mixed $dividend, mixed $divisor): array|string|float
      *
      * Computes x raised to the power y.
      *
-     * @param array|float|int|string $x Or can be an array of values
-     * @param array|float|int|string $y Or can be an array of values
+     * @param null|array|bool|float|int|string $x Or can be an array of values
+     * @param null|array|bool|float|int|string $y Or can be an array of values
      *
      * @return array|float|int|string The result, or a string containing an error
      *         If an array of numbers is passed as an argument, then the returned result will also be an array
      *            with the same dimensions
      */
-    public static function power(array|float|int|string $x, array|float|int|string $y): array|float|int|string
+    public static function power(null|array|bool|float|int|string $x, null|array|bool|float|int|string $y): array|float|int|string
     {
         if (is_array($x) || is_array($y)) {
             return self::evaluateArrayArguments([self::class, __FUNCTION__], $x, $y);

tests/data/Calculation/MathTrig/POWER.php

@@ -410,4 +410,9 @@
     ],
     ['#VALUE!', 'x', 2],
     ['#VALUE!', 2, 'x'],
+    'exponent is null' => [1, 2, null],
+    'base is null' => [0, null, 2],
+    'both null' => ['#NUM!', null, null],
+    'exponent is bool' => [2, 2, true],
+    'base is bool' => [0, false, 2],
 ];