Use NodeFinder to deduplicate assignable AST node traversal

Replace manual recursive traversal of PropertyFetch, MethodCall,
NullsafePropertyFetch, NullsafeMethodCall, StaticPropertyFetch,
and StaticCall in isExpressionDependentOnThis() with NodeFinder
(which uses NodeTraverser+NodeVisitor internally). This eliminates
the per-node-type recursion and makes the traversal reusable.

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

Author: phpstan-bot

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -8,6 +8,7 @@
 use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\MethodCall;
 use PhpParser\Node\Expr\StaticCall;
+use PhpParser\NodeFinder;
 use PHPStan\Analyser\MutatingScope;
 use PHPStan\Analyser\Scope;
 use PHPStan\Analyser\TypeSpecifier;
@@ -408,28 +409,21 @@ private function isExpressionDependentOnTraitContext(Scope $scope, Expr $expr):
 
 	private static function isExpressionDependentOnThis(Expr $expr): bool
 	{
-		if ($expr instanceof Expr\Variable && $expr->name === 'this') {
-			return true;
-		}
-
-		if ($expr instanceof Expr\PropertyFetch || $expr instanceof Expr\NullsafePropertyFetch) {
-			return self::isExpressionDependentOnThis($expr->var);
-		}
-
-		if ($expr instanceof Expr\MethodCall || $expr instanceof Expr\NullsafeMethodCall) {
-			return self::isExpressionDependentOnThis($expr->var);
-		}
-
-		if ($expr instanceof Expr\StaticPropertyFetch || $expr instanceof Expr\StaticCall) {
-			if ($expr->class instanceof Expr) {
-				return self::isExpressionDependentOnThis($expr->class);
+		return (new NodeFinder())->findFirst($expr, static function (Node $node): bool {
+			if ($node instanceof Expr\Variable && $node->name === 'this') {
+				return true;
 			}
 
-			$className = $expr->class->toString();
-			return in_array($className, ['self', 'static', 'parent'], true);
-		}
+			if (
+				($node instanceof Expr\StaticPropertyFetch || $node instanceof Expr\StaticCall)
+				&& !$node->class instanceof Expr
+				&& in_array($node->class->toString(), ['self', 'static', 'parent'], true)
+			) {
+				return true;
+			}
 
-		return false;
+			return false;
+		}) !== null;
 	}
 
 	private static function isSpecified(Scope $scope, Expr $node, Expr $expr): bool