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#include <iostream>
#include <functional>
#include <memory>
 
template <typename T, typename V>
int mao(T&& t, V&& v, decltype( (t.*v)(0), (int)0 ) = 0)
{//オブジェクトとメンバーポインタの組み合わせ
	return 0;
}
template <typename T, typename V>
int mao(T&& t, V&& v, decltype( (*t.*v)(0), (char)0 ) = 0)
{//ポインタ（生ポ／スマポ）とメンバーポインタの組み合わせ
	return 1;
}
template <typename T, typename V>
int mao(T&& t, V&& v, ...)
{//それ以外
	return -1;
}
 
struct test	{
	int a;
	test(int b) : a(b) { }
	int get(int b) const { return a+b; }
};
 
int  main()
{
	test a(7);
	std::unique_ptr<test> p(new test(8));
	std::cout << mao(a, &test::get) << std::endl;
	std::cout << mao(&a, &test::get) << std::endl;
	std::cout << mao(p, &test::get) << std::endl;
	return 0;
}

prog.cpp: In function ‘int main()’:
prog.cpp:31:32: error: call of overloaded ‘mao(test&, int (test::*)(int)const)’ is ambiguous
  std::cout << mao(a, &test::get) << std::endl;
                                ^
prog.cpp:31:32: note: candidates are:
prog.cpp:6:5: note: int mao(T&&, V&&, decltype ((*mao::t.**mao::v(0), (int)(0)))) [with T = test&; V = int (test::*)(int)const; decltype ((*mao::t.**mao::v(0), (int)(0))) = int]
 int mao(T&& t, V&& v, decltype( (t.*v)(0), (int)0 ) = 0)
     ^
prog.cpp:16:5: note: int mao(T&&, V&&, ...) [with T = test&; V = int (test::*)(int)const]
 int mao(T&& t, V&& v, ...)
     ^
prog.cpp:32:33: error: call of overloaded ‘mao(test*, int (test::*)(int)const)’ is ambiguous
  std::cout << mao(&a, &test::get) << std::endl;
                                 ^
prog.cpp:32:33: note: candidates are:
prog.cpp:11:5: note: int mao(T&&, V&&, decltype ((**mao::t.**mao::v(0), (char)(0)))) [with T = test*; V = int (test::*)(int)const; decltype ((**mao::t.**mao::v(0), (char)(0))) = char]
 int mao(T&& t, V&& v, decltype( (*t.*v)(0), (char)0 ) = 0)
     ^
prog.cpp:16:5: note: int mao(T&&, V&&, ...) [with T = test*; V = int (test::*)(int)const]
 int mao(T&& t, V&& v, ...)
     ^
prog.cpp:33:32: error: call of overloaded ‘mao(std::unique_ptr<test>&, int (test::*)(int)const)’ is ambiguous
  std::cout << mao(p, &test::get) << std::endl;
                                ^
prog.cpp:33:32: note: candidates are:
prog.cpp:11:5: note: int mao(T&&, V&&, decltype ((**mao::t.**mao::v(0), (char)(0)))) [with T = std::unique_ptr<test>&; V = int (test::*)(int)const; decltype ((**mao::t.**mao::v(0), (char)(0))) = char]
 int mao(T&& t, V&& v, decltype( (*t.*v)(0), (char)0 ) = 0)
     ^
prog.cpp:16:5: note: int mao(T&&, V&&, ...) [with T = std::unique_ptr<test>&; V = int (test::*)(int)const]
 int mao(T&& t, V&& v, ...)
     ^

Standard output is empty