324 constexpr bool has_append(int) { return true; }  in has_append()  function
326 constexpr bool has_append(long) { return false; }  in has_append()  function
334 constexpr bool has_append() {  in has_append()  function
335   static_assert(has_append<It>(0) == has_append_op<It>(0), "must be same");  in has_append()
336   return has_append<It>(0) && has_append_op<It>(0);  in has_append()
344     static_assert(has_append<It>(), "");  in test_sfinae()
348     static_assert(has_append<It>(), "");  in test_sfinae()
359     static_assert(has_append<It>(), "");  in test_sfinae()
363     static_assert(!has_append<It>(), "");  in test_sfinae()
367     static_assert(!has_append<int*>(), "");  in test_sfinae()
370     static_assert(!has_append<char>(), "");  in test_sfinae()
371     static_assert(!has_append<const char>(), "");  in test_sfinae()