libstdc++-v3/testsuite/20_util/is_invocable/value_ext.cc

   1 // Copyright (C) 2016-2021 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-do compile { target c++11 } }
  19
  20 #include <type_traits>
  21
  22 template<typename... T>
  23   constexpr bool is_invocable() { return std::__is_invocable<T...>::value; }
  24
  25 template<typename R, typename... T>
  26   constexpr bool is_invocable_conv(std::true_type)
  27   {
  28     using result_type = typename std::__invoke_result<T...>::type;
  29     return std::is_void<R>::value || std::is_convertible<result_type, R>::value;
  30   }
  31
  32 template<typename R, typename... T>
  33   constexpr bool is_invocable_conv(std::false_type) { return false; }
  34
  35 template<typename R, typename... T>
  36   constexpr bool is_invocable_r()
  37   { return is_invocable_conv<R, T...>(std::__is_invocable<T...>{}); }
  38
  39 #define IS_INVOCABLE_DEFINED
  40 #include "value.cc"