code: function getPossibleTypeNames(generator, property) {
    return generator.context.schema.getPossibleTypes(getNamedType(property.fieldType || property.type)).map(type => type.name);
  }
docs: This exists only to properly generate types for union/interface typed fields that
  do not have inline fragments. This currently can happen and the IR does give us
  a set of fields per type condition unless fragments are used within the selection set.