libstdc++-v3/testsuite/24_iterators/indirect_callable/projected.cc

   1 // Copyright (C) 2019-2020 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-options "-std=gnu++2a" }
  19 // { dg-do compile { target c++2a } }
  20
  21 #include <iterator>
  22
  23 template<typename T>
  24   using PI = std::projected<T, std::identity>;
  25
  26 static_assert(std::same_as<PI<int*>::value_type, int>);
  27 static_assert(std::same_as<decltype(*std::declval<const PI<int*>&>()), int&>);
  28
  29 struct X
  30 {
  31   using value_type = char*;
  32   char* const& operator*() &;
  33 };
  34 static_assert( std::readable<X> );
  35 static_assert(std::same_as<PI<X>::value_type, char*>);
  36 static_assert(std::same_as<decltype(*std::declval<PI<X>&>()), char* const&>);
  37
  38 struct Y;
  39 using PY = std::projected<const Y*, int Y::*>;
  40 static_assert(std::same_as<PY::value_type, int>);
  41 static_assert(std::same_as<decltype(*std::declval<PY&>()), const int&>);