std::optional::reset (3) Linux Manual Page

std::optional<T>::reset – std::optional<T>::reset

Synopsis

void reset() noexcept;
(since C++ 17)

If *this contains a value, destroy that value as if by value().T::~T(). Otherwise, there are no effects.
*this does not contain a value after this call.

See also

assigns contents

operator= (public member function)