Fix variadic parameter after optional

Author: ondrejmirtes

src/Rules/FunctionDefinitionCheck.php

@@ -321,7 +321,7 @@ private function checkRequiredParameterAfterOptional(array $parameterNodes): arr
 				throw new \PHPStan\ShouldNotHappenException();
 			}
 			$parameterName = $parameterNode->var->name;
-			if ($optionalParameter !== null && $parameterNode->default === null) {
+			if ($optionalParameter !== null && $parameterNode->default === null && !$parameterNode->variadic) {
 				$errors[] = RuleErrorBuilder::message(sprintf('Deprecated in PHP 8.0: Required parameter $%s follows optional parameter $%s.', $parameterName, $optionalParameter))->line($parameterNode->getStartLine())->nonIgnorable()->build();
 				continue;
 			}

tests/PHPStan/Rules/Functions/data/required-parameter-after-optional.php

@@ -18,3 +18,7 @@ function doBaz(int $foo = 1, $bar): void // not OK
 function doLorem(bool $foo = true, $bar): void // not OK
 {
 }
+
+function doIpsum(bool $foo = true, ...$bar): void // OK
+{
+}