libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03, c++11
  10 // <experimental/type_traits>
  11
  12 #include <experimental/type_traits>
  13 #include <string>
  14
  15 #include "test_macros.h"
  16
  17 namespace ex = std::experimental;
  18
  19 template <typename T>
  20   using copy_assign_t = decltype(std::declval<T&>() = std::declval<T const &>());
  21
  22 struct not_assignable {
  23     not_assignable & operator=(const not_assignable&) = delete;
  24 };
  25
  26 template <typename T, bool b>
  27 void test() {
  28     static_assert( b == ex::is_detected  <copy_assign_t, T>::value, "" );
  29     static_assert( b == ex::is_detected_v<copy_assign_t, T>, "" );
  30 }
  31
  32 int main(int, char**) {
  33     test<int, true>();
  34     test<std::string, true>();
  35     test<not_assignable, false>();
  36
  37   return 0;
  38 }