Variant type from abstract module signature gives a warning

#1 
module type EstablishmentType = {
  type profession;

  /* This works, but then it's not abstract. */
  /*
   type profession =
     | Teacher
     | Director;
    */

  let getProfession: profession => string;
};

module School: EstablishmentType = {
  /*
    type profession = ... is marked with the following warning:

   "Warning 37: constructor Director is never used to build values.
   (However, this constructor appears in patterns.)"
   */
  type profession =
    | Teacher
    | Director;

  let getProfession = person =>
    switch (person) {
    | Teacher => "A teacher"
    | Director => "A director"
    };
};
#2

That’s a valid warning. This code is not actually building any values of the type profession. If you add a build function (or make the type definition public) the warning should go away.

#3

I understand.

Thanks