libstdc++-v3/testsuite/20_util/shared_ptr/modifiers/reset_sfinae.cc

   1 // Copyright (C) 2016-2020 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-do compile { target c++11 } }
  19
  20 #include <memory>
  21
  22 template<typename T, typename Args, typename = void>
  23   struct resettable
  24   : std::false_type
  25   { };
  26
  27 template<typename... T> struct type_list { };
  28
  29 template<typename T, typename... Args>
  30   using reset_result
  31     = decltype(std::shared_ptr<T>{}.reset(std::declval<Args>()...));
  32
  33 template<typename T, typename... Args>
  34   struct resettable<T, type_list<Args...>, reset_result<T, Args...>>
  35   : std::true_type
  36   { };
  37
  38 template<typename T, typename... Args>
  39 constexpr bool can_reset()
  40 { return resettable<T, type_list<Args...>>::value; }
  41
  42 template<typename T>
  43 struct Deleter {
  44   void operator()(T*) const;
  45 };
  46
  47 template<typename T>
  48 using Alloc = std::allocator<T>;
  49
  50 struct Base { };
  51 struct Derived : Base { };
  52
  53 // Positive cases:
  54
  55 static_assert( can_reset<const void, void*>(),
  56     "void* convertible to const void*");
  57 static_assert( can_reset<const int, int*>(),
  58     "int* convertible to const int*");
  59 static_assert( can_reset<Base, Derived*>(),
  60     "Derived* convertible to Base*");
  61 static_assert( can_reset<const Base, Derived*>(),
  62     "Derived* convertible to const Base*");
  63
  64 // Negative cases:
  65
  66 static_assert( !can_reset<int, void*>(),
  67     "void* not convertible to int*");
  68 static_assert( !can_reset<int, void*, Deleter<int>>(),
  69     "void* not convertible to int*");
  70 static_assert( !can_reset<int, void*, Deleter<int>, Alloc<int>>(),
  71     "void* not convertible to int*");
  72
  73 static_assert( !can_reset<int, const int*>(),
  74     "const int* not convertible to int*");
  75 static_assert( !can_reset<int, const int*, Deleter<int>>(),
  76     "const int* not convertible to int*");
  77 static_assert( !can_reset<int, const int*, Deleter<int>, Alloc<int>>(),
  78     "const int* not convertible to int*");
  79
  80 static_assert( !can_reset<int, long*>(),
  81     "long* not convertible to int*");
  82 static_assert( !can_reset<int, long*, Deleter<int>>(),
  83     "long* not convertible to int*");
  84 static_assert( !can_reset<int, long*, Deleter<int>, Alloc<int>>(),
  85     "long* not convertible to int*");
  86
  87 static_assert( !can_reset<Derived, Base*>(),
  88     "Base* not convertible to Derived*");
  89 static_assert( !can_reset<Derived, Base*, Deleter<int>>(),
  90     "Base* not convertible to Derived*");
  91 static_assert( !can_reset<Derived, Base*, Deleter<int>, Alloc<int>>(),
  92     "Base* not convertible to Derived*");