ResultOr<T> not supported Implicit construction

[Dup4]

Like std::make_shared<T>(), it support implicit construction.

such as, bad case:

auto f = []() -> ResultOr<std::shared_ptr<int>> {
    return nullptr;
};

good case:

auto f = []() -> ResultOr<std::shared_ptr<int>> {
    return std::shared_ptr<int>(nullptr);
};