17 Language support library [language.support]

17.12 Coroutines [support.coroutine]

17.12.3 Class template coroutine_­handle [coroutine.handle]

17.12.3.3 Observers [coroutine.handle.observers]

constexpr explicit operator bool() const noexcept;
Returns: address() != nullptr.
bool done() const;
Requires: *this refers to a suspended coroutine.
Returns: true if the coroutine is suspended at its final suspend point, otherwise false.