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#include <iostream>
 
using namespace std;
 
 
class foo
{
public:
	int bar;
};
 
template <class C, C>
class Check;
 
template <class T, class Enable = void>
class enable_if_has_bar
{};
 
template <class T>
class enable_if_has_bar<T, Check <decltype(&T::bar),&T::bar>>
{
public:
	typedef decltype(static_cast<T*>(0)->*static_cast<decltype(&T::bar)>(0)) type;
};
 
template <class T>
typename enable_if_has_bar<T>::type ReturnBar (const T& value)
{
	return value.bar;
}
 
int main ()
{
	foo foobar;
	foobar.bar = 42;
 
	cout << ReturnBar(foobar) << endl;
	return 0;
}

prog.cpp:20:57: error: 'decltype (& T:: bar)' is not a valid type for a template constant parameter
prog.cpp:20:60: error: template argument 2 is invalid
prog.cpp: In function 'int main()':
prog.cpp:37:26: error: no matching function for call to 'ReturnBar(foo&)'

Standard output is empty