type Person = 
  { Name : string
    Age : int }

module CheckedPerson = 
  type CheckedPerson = 
    private | CP of Person
    member x.Person = let (CP p) = x in p
    static member Create(p:Person) = 
      if p.Name = "Yoda" then Some (CP p)
      elif p.Age < 100 then Some (CP p)
      else None

open CheckedPerson

// CP is not publicly accessible; we cannot 
// create CheckedPerson directly
CP { Name = "Tomas"; Age = 999 }

// This compiles, but returns None
CheckedPerson.Create { Name = "Tomas"; Age = 999 }

// This works, extra business rules satisfied
CheckedPerson.Create { Name = "Tomas"; Age = 99 }
CheckedPerson.Create { Name = "Yoda"; Age = 700 }