qiskit/qasm/qasmparser.py
def p_expression_1(self, program):
        """
            expression : '-' expression %prec negative
                        | '+' expression %prec positive
        """
        program[0] = node.Prefix([node.UnaryOperator(program[1]), program[2]])
def p_expression_1(self, program):
        """
            expression : '-' expression %prec negative
                        | '+' expression %prec positive
        """
        program[0] = node.Prefix([node.UnaryOperator(program[1]), program[2]])
expression : '-' expression %prec negative
                        | '+' expression %prec positive