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#include <iostream>
#include <type_traits>
 
template<typename T>
typename std::enable_if<
    std::is_const<typename std::remove_reference<T>::type>::value
>::type
forwarder(T&& x)
{
	auto value_cat = std::is_rvalue_reference<decltype(x)>::value ? "r" : "l";
    std::cout << value_cat << "value reference to const\n";
}
 
int main()
{
    const int x = 42;
    forwarder(std::move(x));
    forwarder(x);
    int y = 42;
    forwarder(std::move(y));
    forwarder(y);
}

prog.cpp: In function ‘int main()’:
prog.cpp:20:27: error: no matching function for call to ‘forwarder(std::remove_reference<int&>::type)’
     forwarder(std::move(y));
                           ^
prog.cpp:20:27: note: candidate is:
prog.cpp:8:1: note: template<class T> typename std::enable_if<std::is_const<typename std::remove_reference< <template-parameter-1-1> >::type>::value>::type forwarder(T&&)
 forwarder(T&& x)
 ^
prog.cpp:8:1: note:   template argument deduction/substitution failed:
prog.cpp: In substitution of ‘template<class T> typename std::enable_if<std::is_const<typename std::remove_reference< <template-parameter-1-1> >::type>::value>::type forwarder(T&&) [with T = int]’:
prog.cpp:20:27:   required from here
prog.cpp:8:1: error: no type named ‘type’ in ‘struct std::enable_if<false, void>’
prog.cpp:21:16: error: no matching function for call to ‘forwarder(int&)’
     forwarder(y);
                ^
prog.cpp:21:16: note: candidate is:
prog.cpp:8:1: note: template<class T> typename std::enable_if<std::is_const<typename std::remove_reference< <template-parameter-1-1> >::type>::value>::type forwarder(T&&)
 forwarder(T&& x)
 ^
prog.cpp:8:1: note:   template argument deduction/substitution failed:
prog.cpp: In substitution of ‘template<class T> typename std::enable_if<std::is_const<typename std::remove_reference< <template-parameter-1-1> >::type>::value>::type forwarder(T&&) [with T = int&]’:
prog.cpp:21:16:   required from here
prog.cpp:8:1: error: no type named ‘type’ in ‘struct std::enable_if<false, void>’

Standard output is empty