Refactor ThisDependentNodeVisitor with reusable static methods

Extract isThisVariable() and isStaticClassReference() as public static
utility methods, and add containsThisDependentExpression() convenience
method. Reuse isThisVariable() in InvalidAssignVarRule instead of
inline $this check.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -8,7 +8,6 @@
 use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\MethodCall;
 use PhpParser\Node\Expr\StaticCall;
-use PhpParser\NodeTraverser;
 use PHPStan\Analyser\MutatingScope;
 use PHPStan\Analyser\Scope;
 use PHPStan\Analyser\TypeSpecifier;
@@ -422,12 +421,7 @@ private function isExpressionDependentOnTraitContext(Scope $scope, Expr $expr):
 
 	private static function isExpressionDependentOnThis(Expr $expr): bool
 	{
-		$visitor = new ThisDependentNodeVisitor();
-		$traverser = new NodeTraverser();
-		$traverser->addVisitor($visitor);
-		$traverser->traverse([$expr]);
-
-		return $visitor->isFound();
+		return ThisDependentNodeVisitor::containsThisDependentExpression($expr);
 	}
 
 	private static function isSpecified(Scope $scope, Expr $node, Expr $expr): bool

src/Rules/Comparison/ThisDependentNodeVisitor.php

@@ -7,6 +7,7 @@
 use PhpParser\Node\Expr;
 use PhpParser\Node\Expr\Variable;
 use PhpParser\Node\Name;
+use PhpParser\NodeTraverser;
 use PhpParser\NodeVisitorAbstract;
 use function in_array;
 
@@ -15,6 +16,28 @@ final class ThisDependentNodeVisitor extends NodeVisitorAbstract
 
 	private bool $found = false;
 
+	public static function isThisVariable(Node $node): bool
+	{
+		return $node instanceof Variable && $node->name === 'this';
+	}
+
+	public static function isStaticClassReference(Node $node): bool
+	{
+		return ($node instanceof Expr\StaticPropertyFetch || $node instanceof Expr\StaticCall)
+			&& $node->class instanceof Name
+			&& in_array($node->class->toString(), ['self', 'static', 'parent'], true);
+	}
+
+	public static function containsThisDependentExpression(Expr $expr): bool
+	{
+		$visitor = new self();
+		$traverser = new NodeTraverser();
+		$traverser->addVisitor($visitor);
+		$traverser->traverse([$expr]);
+
+		return $visitor->isFound();
+	}
+
 	#[Override]
 	public function beforeTraverse(array $nodes): ?array
 	{
@@ -25,16 +48,7 @@ public function beforeTraverse(array $nodes): ?array
 	#[Override]
 	public function enterNode(Node $node): ?int
 	{
-		if ($node instanceof Variable && $node->name === 'this') {
-			$this->found = true;
-			return self::STOP_TRAVERSAL;
-		}
-
-		if (
-			($node instanceof Expr\StaticPropertyFetch || $node instanceof Expr\StaticCall)
-			&& $node->class instanceof Name
-			&& in_array($node->class->toString(), ['self', 'static', 'parent'], true)
-		) {
+		if (self::isThisVariable($node) || self::isStaticClassReference($node)) {
 			$this->found = true;
 			return self::STOP_TRAVERSAL;
 		}

src/Rules/Operators/InvalidAssignVarRule.php

@@ -9,6 +9,7 @@
 use PhpParser\Node\Expr\AssignRef;
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Rules\Comparison\ThisDependentNodeVisitor;
 use PHPStan\Rules\NullsafeCheck;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
@@ -72,7 +73,7 @@ public function processNode(Node $node, Scope $scope): array
 	private function containsNonAssignableExpression(Expr $expr): bool
 	{
 		if ($expr instanceof Expr\Variable) {
-			return $expr->name === 'this';
+			return ThisDependentNodeVisitor::isThisVariable($expr);
 		}
 
 		if ($expr instanceof Expr\PropertyFetch) {