Fix ThrowExpressionRule

Author: ondrejmirtes

conf/config.neon

@@ -334,6 +334,11 @@ services:
 		tags:
 			- phpstan.parser.richParserNodeVisitor
 
+	-
+		class: PHPStan\Parser\StandaloneThrowExprVisitor
+		tags:
+			- phpstan.parser.richParserNodeVisitor
+
 	-
 		class: PHPStan\Parser\TryCatchTypeVisitor
 		tags:

src/Parser/StandaloneThrowExprVisitor.php

@@ -0,0 +1,28 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Parser;
+
+use PhpParser\Node;
+use PhpParser\NodeVisitorAbstract;
+
+class StandaloneThrowExprVisitor extends NodeVisitorAbstract
+{
+
+	public const ATTRIBUTE_NAME = 'standaloneThrowExpr';
+
+	public function enterNode(Node $node)
+	{
+		if (!$node instanceof Node\Stmt\Expression) {
+			return null;
+		}
+
+		if (!$node->expr instanceof Node\Expr\Throw_) {
+			return null;
+		}
+
+		$node->expr->setAttribute(self::ATTRIBUTE_NAME, true);
+
+		return $node;
+	}
+
+}

src/Rules/Exceptions/ThrowExpressionRule.php

@@ -4,6 +4,7 @@
 
 use PhpParser\Node;
 use PHPStan\Analyser\Scope;
+use PHPStan\Parser\StandaloneThrowExprVisitor;
 use PHPStan\Php\PhpVersion;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
@@ -29,6 +30,10 @@ public function processNode(Node $node, Scope $scope): array
 			return [];
 		}
 
+		if ($node->getAttribute(StandaloneThrowExprVisitor::ATTRIBUTE_NAME) === true) {
+			return [];
+		}
+
 		return [
 			RuleErrorBuilder::message('Throw expression is supported only on PHP 8.0 and later.')->nonIgnorable()
 				->identifier('throw.notSupported')