fix: Convert to timezone with own utility function

Author: pl-github

src/TypeGuard.php

@@ -124,16 +124,14 @@ public function asDateTimeImmutable(mixed $value, DateTimeZone|string|null $time
             return null;
         }
 
-        $tz = $timeZone instanceof DateTimeZone
-            ? $timeZone
-            : ($timeZone !== null ? new DateTimeZone($timeZone) : $this->timeZone());
+        $timeZone = $this->asDateTimeZone($timeZone) ?? $this->timeZone();
 
         if ($value instanceof DateTimeImmutable) {
-            if ($value->getTimezone()->getName() === $tz->getName()) {
+            if ($value->getTimezone()->getName() === $timeZone->getName()) {
                 return $value;
             }
 
-            return $value->setTimezone($tz);
+            return $value->setTimezone($timeZone);
         }
 
         if ($value instanceof Stringable) {
@@ -144,7 +142,7 @@ public function asDateTimeImmutable(mixed $value, DateTimeZone|string|null $time
             throw NotConvertable::toDateTime($value);
         }
 
-        return new DateTimeImmutable(asString($value), $tz);
+        return new DateTimeImmutable(asString($value), $timeZone);
     }
 
     /** @return ($value is null ? null : DateTimeZone) */

tests/AsDateTimeImmutableTest.php

@@ -145,7 +145,7 @@ public function testNullTimezoneParameterUsesDefault(): void
     {
         TypeGuard::instance()->timeZone('Australia/Adelaide');
 
-        $result = asDateTimeImmutable('2010-09-08 07:06:05', null);
+        $result = asDateTimeImmutable('2010-09-08 07:06:05');
 
         self::assertInstanceOf(DateTimeImmutable::class, $result);
         self::assertSame('2010-09-08T07:06:05+09:30', $result->format('c'));