Method create

tests/test_smart_ptr.cpp:260–260

struct SftVirtDerived : SftVirtBase {
    using SftVirtBase::SftVirtBase;
    static std::shared_ptr<SftVirtDerived> create() { return std::make_shared<SftVirtDerived>(); }
    std::string name() override { return "SftVirtDerived"; }
};
struct SftVirtDerived2 : virtual SftVirtDerived {