Review

class DisambiguateProperties {
  /**
   * Invalidates the given type, so that no properties on it will be renamed.
   */
  private void addInvalidatingType(JSType type) {
    type = type.restrictByNotNullOrUndefined();
    if (type instanceof UnionType) {
      for (JSType alt : ((UnionType) type).getAlternates()) {
        addInvalidatingType(alt);
      }
      return;
    }

    typeSystem.addInvalidatingType(type);
    ObjectType objType = ObjectType.cast(type);
    if (objType != null && objType.getImplicitPrototype() != null) {
      typeSystem.addInvalidatingType(objType.getImplicitPrototype());
    }
  }
}

class DisambiguateProperties.TypeSystem {
    /**
     * Informs the given type system that a type is invalidating due to a type
     * mismatch found during type checking.
     */
    void addInvalidatingType(JSType type);
}

class DisambiguateProperties.JSTypeSystem {
    @Override public void addInvalidatingType(JSType type) {
      checkState(!type.isUnionType());
      invalidatingTypes.add(type);
    }
}

class DisambiguateProperties.ConcreteTypeSystem {
    @Override public void addInvalidatingType(JSType type) {
      checkState(!type.isUnionType());
      invalidatingTypes.add(type);
    }

}