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// PR c++/66092
// { dg-do compile { target c++17_only } }
// { dg-options "-fconcepts" }
#include <type_traits>
template <typename T, typename U, typename... Args>
requires (sizeof...(Args) == 0)
constexpr decltype(auto) check()
{
return std::integral_constant<bool, __is_same_as(T, U)>();
}
template <typename T, typename U, typename... Args>
requires (sizeof...(Args) > 0)
constexpr decltype(auto) check()
{
return std::integral_constant<bool, __is_same_as(T, U)
&& decltype(check<U, Args...>())::value>();
}
template <typename T, typename U, typename... Args>
concept bool Same()
{
return decltype(check<T, U, Args...>())::value;
}
template <typename T, typename U, typename... Args>
concept bool Similar = true;
template <typename... Args>
requires Same<Args...>() // { dg-error "" "" { xfail *-*-* } }
void foo( Args... args ) {}
// FIXME: The new method of building concept checks is suppressing the
// diagnostic for the invalid substitution. This produces an invalid
// requires-clause, which still prevents the function from being resolved.
template <typename... Args>
requires Similar<Args...> // { dg-error "pack expansion" }
void bar( Args... args ) {}
int main()
{
foo(1, 2, 3); // { dg-error "" }
bar(1, 2, 3); // { dg-error "" }
}
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