// This qualifier saves the day; solve constraints WITHOUT IT
// qualif Zog(v:a) : (10 <= v)

constraint:
  env [a : {v : int | (exists x:int. x=10 /\ v=x) 
                   \/ (exists y:int. y=20 /\ v=y) }]
  lhs {v : int | v = a  }
  rhs {v : int | 10 <= v}
  id 3 

/*

Rewriting constraints as:

    id 1
    x:int, v:int |- (v=10)[x/v] /\ (v=x) => k0
    x:int, v:int |- (x=10) /\ (v=x) => k0

    id 2
    y:int, v:int |- (v=20)[y/v] /\ (v=y) => k0
    y:int, v:int |- (y=20) /\ (v=y) => k0

Projecting out all variables NOT in the WF of k0

    id 1
    v:int |- (exists x:int. x=10 /\ v=x) => k0

    id 2
    v:int |- (exists y:int. y=20 /\ v=y) => k0

Take the \/ of all constraints on k0

    k0 = (exists x:int. x=10 /\ v=x) \/ (exists y:int. y=20 /\ v=y)
     
So you get:

    env [a : {v : int | (exists x:int. x=10 /\ v=x) \/ (exists y:int. y=20 /\ v=y) }]
      lhs {v : int | v = a  }
    rhs {v : int | 10 <= v}
    id 3

*/