setOperator example

while (true) {
                $combinator = $this->consumeCombinator();
                if (!$first && !$combinator) {
                    break;
                }
                $parts = $this->parseSelectorParts();
                if (!count($parts)) {
                    throw new Exception("Missing selector after combinator");
                }
                $first = false;
                $selCombinator = new Node\Combinator;
                $selCombinator->setOperator(
                    $combinator ?: ($filter ? null : " ")
                );
                foreach ($parts as $part) {
                    $selCombinator->addPart($part);
                }
                $group->addCombinator($selCombinator);
            }
            $selector->addGroup($group);
            $this->consumeWhitespaces();
        } while ($this->consume(","));
        return $selector;
    }

"Optional chain can't appear in left-hand side"
                        );
                    }

                    $right = $this->parseAssignmentExpression();
                    
                    if ($right) {
                        $node = $this->createNode(
                            "AssignmentExpression", $expr
                        );
                        $node->setLeft($this->expressionToPattern($expr));
                        $node->setOperator($operator->value);
                        $node->setRight($right);
                        return $this->completeNode($node);
                    }
                    $this->error();
                }
            }
            return $expr;
        }
        return null;
    }