any.cc

class AssociatedFrobnicator : public base::SupportsUserData::Data {
 public:
  Frobnicator* frobnicator() const { return frobnicator_; }
  void set_frobnicator(Frobnicator* frobnicator) const { frobnicator_ = frobnicator; }
 private:
  Frobnicator* frobnicator_;
};

base::SupportsUserData::Data* data;
static_cast<AssociatedFrobnicator*>(data)->set_frobnicator(new_frobnicator);


std::any& data;
any_cast<Frobnicator*&>(data) = new_frobnicator;