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// PR c++/56782
// { dg-do compile { target c++11 } }
template<class T>
T&& declval();
struct is_convertible_impl {
template<class T>
static void sink(T);
template<class T, class U, class = decltype(sink<U>(declval<T>()))>
static auto test(int) -> char;
template<class, class>
static auto test(...) -> char(&)[2];
};
template<class T, class U>
struct is_convertible : is_convertible_impl
{
static const bool value = sizeof(test<T, U>(0)) == 1;
};
template<bool, class>
struct enable_if {};
template<class T>
struct enable_if<true, T> { typedef T type; };
template<bool, class If, class Else>
struct conditional { typedef If type; };
template<class If, class Else>
struct conditional<false, If, Else> { typedef Else type; };
template<class...>
struct and_;
template<>
struct and_<>
{
static const bool value = true;
};
template<class P>
struct and_<P> : P
{
};
template<class P1, class P2>
struct and_<P1, P2> : conditional<P1::value, P2, P1>::type
{
};
template<class... T>
struct Tuple {
template<class... U,
class = typename enable_if<and_<is_convertible<U, T>... >::value, int>::type
>
Tuple(U&&...){}
};
static_assert(is_convertible<Tuple<>, Tuple<>>::value, "Ouch"); //#1
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