libcxx/test/std/experimental/utilities/meta/meta.detect/detected_or.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 hasFoo = typename T::Foo;
  21
  22 struct yesFoo {
  23     using Foo = int;
  24 };
  25
  26 struct noFoo {
  27 };
  28
  29
  30 template <typename T, typename Res>
  31 void test() {
  32     static_assert( std::is_same<Res, typename ex::detected_or  <double, hasFoo, T>::type>::value, "" );
  33     static_assert( std::is_same<Res, typename ex::detected_or_t<double, hasFoo, T>      >::value, "" );
  34 }
  35
  36 int main(int, char**) {
  37     test<yesFoo, int>();
  38     test<noFoo, double>();
  39
  40   return 0;
  41 }