src/Parser/Parser.php
protected function parsePrimary(array $unary, Node $operand): Node
    {
        foreach (\array_reverse($unary) as $operator) {
            $operand = new UnaryOperator($operator->type, $operand);
        }
        
        return $operand;
    }
protected function parsePrimary(array $unary, Node $operand): Node
    {
        foreach (\array_reverse($unary) as $operator) {
            $operand = new UnaryOperator($operator->type, $operand);
        }
        
        return $operand;
    }
Primary ::= ( '-' | 'not' | 'empty' )+ Operand