Constraint is volatile when using if decision on chain constraint of string-type

[LeeKaiXuan]

Description

When a string-type variable is constrained by someone (e.g., tf in example) and then the variable will constraint another (e.g., bar in example), the if decision that constraints the string-type variable become incorrect. Thus, the entire constraint block volatiles the user's expectation.

Scenario Code

component pss_top {
    action root_a {
        activity {
            do chainConstraintWithString with { tf in [1]; };
        }
    }

    action chainConstraintWithString {
        rand bit tf;
        rand string foo;
        rand int bar;

        constraint {
            if (tf in [1]) {
                foo in ["foo"];
            } else {
                foo in ["oof"];
            }
            if (foo in ["foo"]) {
                bar in [100];
            } else if (foo in ["oof"]) {
                bar in [200];
            } else {
                bar in [300];
            }
        }
        exec body ASM = """chainConstraintWithString: {{tf}} ; {{foo}} ; {{bar}}""";
    }
}

Expected Output or Behaviour

constraintBySet: 1 ; foo ; 100

Error Message from PSSGen or JAVA

1c1
< chainConstraintWithString: 1 ; oof ; 200
---
> constraintBySet: 1 ; foo ; 100