libstdc++-v3/testsuite/20_util/function_objects/identity/1.cc

   1 // Copyright (C) 2019-2024 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++20 } }
  19
  20 #include <functional>
  21
  22 // C++20 [func.identity]
  23 static_assert( std::is_default_constructible_v<std::identity> );
  24 static_assert( std::is_copy_constructible_v<std::identity> );
  25 static_assert( std::is_move_constructible_v<std::identity> );
  26 static_assert( std::is_copy_assignable_v<std::identity> );
  27 static_assert( std::is_move_assignable_v<std::identity> );
  28
  29 static_assert( !std::is_invocable_v<std::identity> );
  30 static_assert( !std::is_invocable_v<std::identity, int&, int&> );
  31 static_assert( std::is_nothrow_invocable_r_v<int&, std::identity&, int&> );
  32 static_assert( std::is_nothrow_invocable_r_v<const long&, std::identity, const long&> );
  33 static_assert( std::is_nothrow_invocable_r_v<short&&, const std::identity&, short> );
  34 static_assert( std::is_nothrow_invocable_r_v<const char&&, const std::identity, const char> );
  35
  36 int i;
  37 static_assert( std::addressof(std::identity{}(i)) == std::addressof(i) );
  38
  39 using T = std::identity::is_transparent; // required typedef