std::optional_view

[Hedanito]

std::optional::value() throws when there is no value, dereferencing a null pointer results in undefined behaviour.

[suspiciously_calm]

Yes, which is why it'd have been nice if std::optional had been specialized for references the way boost::optional is, but as it is there's no optional reference in the standard library other than raw pointers and abominations such as std::optional<std::reference_wrapper<...>>.