grammar                                      // t1
          -> Expression, end                         // rule 1 = t2, t3

        Expression                                   // t2
          -> option, Primary                         // rule 2 = t4, t5

        Primary                                      // t5
           -> Value                                  // rule 3 = t6
           -> "(", Expression, ")"             // rule 4 = t7, t2, t8

        option                                       // t4
          ->
          -> unary op                                // rule 6 = t9

        Value                                        // t6
          -> ConstraintValue, ValueAttributes        // rule 7 = t10, t11

        ConstraintValue                              // t10
          -> Expression                              // rule 8 = t12