https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90711
--- Comment #1 from David Hunt <da_cra_hunt at yahoo dot com> ---
Self-contained :
---
namespace test {
void EXISTS(int);
}
template<typename... ARGS>
struct stub_void {
typedef void type;
};
template<typename... ARGS>
using stub_void_t = typename stub_void<ARGS...>::type;
#if !defined(SUPPRESS)
template<typename O, typename = void>
struct has_to_string {
static constexpr bool value = false;
};
template<typename O>
struct has_to_string<O, stub_void_t<decltype(EXISTS(O{}))>> {
static constexpr bool value = true;
};
#endif
template<typename O, typename = void>
struct has_std_to_string {
static constexpr bool value = false;
};
template<typename O>
struct has_std_to_string<O, stub_void_t<decltype(test::EXISTS(O{}))>> {
static constexpr bool value = true;
};
int main(int argc, char *argv[]) {
return has_std_to_string<int>::value;
}
---
