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#include <algorithm>
#include <iterator>
#include <vector>
#include <iostream>
#include <array>
 
template<typename T>
struct TypeCheck;
 
 
int main()
{
	{
	std::vector<int> vec{1};
	auto val = vec.begin();
	auto check = TypeCheck<decltype(val)>{};
	}
 
	{
	std::vector<bool> vec{true};
	auto val = vec.begin();
	auto check = TypeCheck<decltype(val)>{};
	}
 
	{
	std::array<int, 1> vec{1};
	auto val = vec.begin();
	auto check = TypeCheck<decltype(val)>{};
	}
 
	{
	std::array<bool, 1> vec{false};
	auto val = vec.begin();
	auto check = TypeCheck<decltype(val)>{};
	}
}

prog.cpp: In function 'int main()':
prog.cpp:16:40: error: invalid use of incomplete type 'struct TypeCheck<__gnu_cxx::__normal_iterator<int*, std::vector<int> > >'
  auto check = TypeCheck<decltype(val)>{};
                                        ^
prog.cpp:8:8: note: declaration of 'struct TypeCheck<__gnu_cxx::__normal_iterator<int*, std::vector<int> > >'
 struct TypeCheck;
        ^
prog.cpp:22:40: error: invalid use of incomplete type 'struct TypeCheck<std::_Bit_iterator>'
  auto check = TypeCheck<decltype(val)>{};
                                        ^
prog.cpp:8:8: note: declaration of 'struct TypeCheck<std::_Bit_iterator>'
 struct TypeCheck;
        ^
prog.cpp:28:40: error: invalid use of incomplete type 'struct TypeCheck<int*>'
  auto check = TypeCheck<decltype(val)>{};
                                        ^
prog.cpp:8:8: note: declaration of 'struct TypeCheck<int*>'
 struct TypeCheck;
        ^
prog.cpp:34:40: error: invalid use of incomplete type 'struct TypeCheck<bool*>'
  auto check = TypeCheck<decltype(val)>{};
                                        ^
prog.cpp:8:8: note: declaration of 'struct TypeCheck<bool*>'
 struct TypeCheck;
        ^

Standard output is empty