fork download

#include <tuple>
#include <cstddef>
#include <utility>
#include <iostream>
 
enum class XParameters : unsigned int
{
	PARAMETER1, // int
	PARAMETER2, // float
	MAX,
};
 
enum class YParameters : unsigned int
{
	PARAMETER3 = XParameters::MAX // std::string
};
 
using XTuple = std::tuple<int, float>;
using YAttributes = std::tuple<std::string>;
using YTuple = decltype(tuple_cat(XTuple(), YAttributes()));
 
template <typename Attributes>
struct Common
{
	Common(Attributes&& attr) : attributes(std::move(attr)) {}
 
	Attributes attributes;
 
	template <typename AttributeName>
    auto GetAttribute(AttributeName attributeName) -> decltype(std::declval(std::get<static_cast<size_t>(attributeName)>(attributes)))
    {
    	return std::get<static_cast<size_t>(attributeName)>(attributes);
    }
};
 
struct X : Common<XTuple>
{
	X() : Common(std::make_tuple(42, 3.14f)) {}
};
 
struct Y : Common<YTuple>
{
	Y() : Common(std::make_tuple(666, 0.01f, "string")) {}
};
 
int main()
{
	X x;
	Y y;
 
	int parameter1 = std::get<static_cast<size_t>(XParameters::PARAMETER1)>(x.attributes); // Compiles, works.
	std::cout << parameter1 << std::endl;
 
	std::string parameter3 = std::get<static_cast<size_t>(YParameters::PARAMETER3)>(y.attributes); // Compiles, works.
	std::cout << parameter3 << std::endl;
 
	x.GetAttribute(XParameters::PARAMETER1); // Does not compile.
 
	//parameter3 = std::get<static_cast<size_t>(YParameters::PARAMETER3)>(x.attributes); // Does not compile, phew...
 
 
 
 
	return 0;
}

prog.cpp:30:119: error: invalid operands of types '<unresolved overloaded function type>' and 'size_t {aka unsigned int}' to binary 'operator<'
     auto GetAttribute(AttributeName attributeName) -> decltype(std::declval(std::get<static_cast<size_t>(attributeName)>(attributes)))
                                                                                                                       ^
prog.cpp:30:119: error: invalid operands of types '<unresolved overloaded function type>' and 'size_t {aka unsigned int}' to binary 'operator<'
prog.cpp: In function 'int main()':
prog.cpp:57:4: error: 'struct X' has no member named 'GetAttribute'
  x.GetAttribute(XParameters::PARAMETER1); // Does not compile.
    ^

Standard output is empty