User::addRole

public User::addRole($rid)

public function addRole($rid) {

  if (in_array($rid, [RoleInterface::AUTHENTICATED_ID, RoleInterface::ANONYMOUS_ID])) {
    throw new \InvalidArgumentException('Anonymous or authenticated role ID must not be assigned manually.');
  }

  $roles = $this->getRoles(TRUE);
  $roles[] = $rid;
  $this->set('roles', array_unique($roles));
}