libstdc++-v3/testsuite/20_util/tuple/comparison_operators/overloaded2.cc

   1 // { dg-do compile { target c++11 } }
   2
   3 // Copyright (C) 2014-2021 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING3.  If not see
  18 // <http://www.gnu.org/licenses/>.
  19
  20 #include <tuple>
  21
  22 // A type that is contextually convertible to bool but cannot be used with
  23 // the usual logical operators, and/or/not.
  24 struct TwistedLogic {
  25   bool value;
  26
  27   explicit operator bool() const noexcept { return value; }
  28 };
  29
  30 template<typename T>
  31 bool operator&&(const T&, TwistedLogic) = delete;
  32
  33 template<typename T>
  34 bool operator&&(TwistedLogic, const T&) = delete;
  35
  36 template<typename T>
  37 bool operator||(const T&, TwistedLogic) = delete;
  38
  39 template<typename T>
  40 bool operator||(TwistedLogic, const T&) = delete;
  41
  42 bool operator!(TwistedLogic) noexcept = delete;
  43
  44 struct Compares {};
  45
  46 TwistedLogic operator==(const Compares&, const Compares&) { return {true}; }
  47 TwistedLogic operator<(const Compares&, const Compares&) { return {false}; }
  48
  49 auto a = std::make_tuple(nullptr, Compares{}, 2, 'U');
  50 auto b = a < a;
  51
  52 // { dg-error "no match for 'operator<'" "" { target c++20 } 0 }
  53 // { dg-error "no match for .*_Synth3way|in requirements" "" { target c++20 } 0 }
  54 // { dg-error "ordered comparison" "" { target c++17_down } 0 }