Templates.hpp

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#pragma once
 
#include <type_traits>
 
// Generate two constexpr templated bools to check if
// a function is a member of a class.
// - has_name<Class, function> to check for simple name existence
// - has_name<Class, function, ret(args...)> to check for existence with signature constraint
#define GENERATE_CHECK_HAS_FUNC(FuncName)                                                     \
template <typename, typename = void, typename = void>                                         \
constexpr bool has_##FuncName = false;                                                        \
                                                                                              \
template <typename T>                                                                         \
constexpr bool has_##FuncName<T,                                                              \
    typename ::std::enable_if_t<::std::is_member_function_pointer_v<decltype(&T::FuncName)>>> \
= true;                                                                                       \
                                                                                              \
template <typename T, typename Ret, typename... Args>                                         \
constexpr bool has_##FuncName<T, Ret(Args...),                                                \
    ::std::void_t<decltype(::std::declval<T>().FuncName(::std::declval<Args>()...))>>         \
= ::std::is_same_v<decltype(::std::declval<T>().FuncName(::std::declval<Args>()...)), Ret>;   \
 static_assert(true, "") /* To require a ; after macro call */