FOLLY_FOR_EACH_THIS_OVERLOAD_IN_CLASS_BODY_DELEGATE

#define FOLLY_FOR_EACH_THIS_OVERLOAD_IN_CLASS_BODY_DELEGATE(MEMBER, DELEGATE)

Description

Helper macro to add 4 delegated, qualifier-overloaded methods to a class

Example:

template <typename T> class optional { public: bool has_value() const;

T& value() & { if (!has_value()) { throw std::bad_optional_access(); } return m_value; }

const T& value() const& { if (!has_value()) { throw std::bad_optional_access(); } return m_value; }

T&& value() && { if (!has_value()) { throw std::bad_optional_access(); } return std::move(m_value); }

const T&& value() const&& { if (!has_value()) { throw std::bad_optional_access(); } return std::move(m_value); } };

This is equivalent to

template <typename T> class optional { template <typename Self> decltype(auto) value_impl(Self&& self) { if (!self.has_value()) { throw std::bad_optional_access(); } return std::forward<Self>(self).m_value; } // ...

public: bool has_value() const;

FOLLY_FOR_EACH_THIS_OVERLOAD_IN_CLASS_BODY_DELEGATE(value, value_impl); };

Note: This can be migrated to C++23's deducing this: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p0847r7.html