libstdc++-v3/testsuite/20_util/variant/visit.cc

   1 // Copyright (C) 2019-2021 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-options "-std=gnu++17" }
  19 // { dg-do run { target c++17 } }
  20
  21 #include <variant>
  22 #include <functional>
  23 #include <testsuite_hooks.h>
  24
  25 // N.B. there are more std::visit tests in ./compile.cc and ./run.cc
  26
  27 void
  28 test01()
  29 {
  30   // Verify that visitation uses INVOKE and supports arbitrary callables.
  31
  32   struct X
  33   {
  34     int sum(int i) const { return i + n; }
  35     int product(int i) const { return i * n; }
  36     int n;
  37   };
  38
  39   std::variant<X, X*, std::reference_wrapper<X>> vobj{X{1}};
  40   int res = std::visit(&X::n, vobj);
  41   VERIFY( res == 1 );
  42
  43   std::variant<int, short> varg{2};
  44   res = std::visit(&X::sum, vobj, varg);
  45   VERIFY( res == 3 );
  46
  47   X x{4};
  48   vobj = &x;
  49   res = std::visit(&X::n, vobj);
  50   VERIFY( res == 4 );
  51
  52   varg.emplace<short>(5);
  53   res = std::visit(&X::sum, vobj, varg);
  54   VERIFY( res == 9 );
  55
  56   x.n = 6;
  57   res = std::visit(&X::product, vobj, varg);
  58   VERIFY( res == 30 );
  59
  60   vobj = std::ref(x);
  61   x.n = 7;
  62   res = std::visit(&X::n, vobj);
  63   VERIFY( res == 7 );
  64
  65   res = std::visit(&X::product, vobj, varg);
  66   VERIFY( res == 35 );
  67 }
  68
  69 void
  70 test02()
  71 {
  72   struct NoCopy
  73   {
  74     NoCopy() { }
  75     NoCopy(const NoCopy&) = delete;
  76     NoCopy(NoCopy&&) = delete;
  77     ~NoCopy() { }
  78
  79     int operator()(int i) { return i; }
  80     int operator()(const NoCopy&) { return 0; }
  81   };
  82
  83   std::variant<NoCopy, int> v{1};
  84   NoCopy f;
  85   // Visit should not need arguments to be copyable:
  86   int res = std::visit(f, v);
  87   VERIFY( res == 1 );
  88 }
  89
  90 int
  91 main()
  92 {
  93   test01();
  94   test02();
  95 }