libstdc++-v3/testsuite/20_util/shared_ptr/assign/sfinae.cc

   1 // Copyright (C) 2016-2021 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-do compile { target c++11 } }
  19
  20 #include <memory>
  21
  22 template<typename T, typename From>
  23 constexpr bool can_assign()
  24 { return std::is_assignable<std::shared_ptr<T>, From>::value; }
  25
  26 struct Base { };
  27 struct Derived : Base { };
  28
  29 // Positive cases:
  30
  31 static_assert( can_assign<const void, const std::shared_ptr<void>&>(),
  32     "void* convertible to const void*");
  33 static_assert( can_assign<const void, std::shared_ptr<void>&&>(),
  34     "void* convertible to const void*");
  35 static_assert( can_assign<const int, std::shared_ptr<int>>(),
  36     "int* convertible to const int*");
  37 static_assert( can_assign<Base, std::shared_ptr<Derived>>(),
  38     "Derived* convertible to Base*");
  39 static_assert( can_assign<const Base, std::shared_ptr<Derived>>(),
  40     "Derived* convertible to const Base*");
  41
  42 // Negative cases:
  43
  44 static_assert( !can_assign<int, const std::shared_ptr<void>&>(),
  45     "void* not convertible to int*");
  46 static_assert( !can_assign<int, std::shared_ptr<void>&&>(),
  47     "void* not convertible to int*");
  48
  49 static_assert( !can_assign<int, const std::shared_ptr<const int>&>(),
  50     "const int* not convertible to int*");
  51 static_assert( !can_assign<int, std::shared_ptr<const int>&&>(),
  52     "const int* not convertible to int*");
  53
  54 static_assert( !can_assign<int, const std::shared_ptr<long>&>(),
  55     "long* not convertible to int*");
  56 static_assert( !can_assign<int, std::shared_ptr<long>&&>(),
  57     "long* not convertible to int*");
  58
  59 static_assert( !can_assign<int, std::unique_ptr<long>&&>(),
  60     "unique_ptr<long>::pointer not convertible to int*");
  61
  62 static_assert( !can_assign<Derived, const std::shared_ptr<Base>&>(),
  63     "Base* not convertible to Derived*");
  64 static_assert( !can_assign<int, std::shared_ptr<long>&&>(),
  65     "Base* not convertible to Derived*");
  66 static_assert( !can_assign<Derived, std::unique_ptr<Base>&&>(),
  67     "unique_ptr<Base>::pointer not convertible to Derived*");
  68
  69 struct Deleter {
  70   using pointer = void*;
  71   void operator()(pointer) const { }
  72 };
  73
  74 static_assert( !can_assign<Derived, std::unique_ptr<Derived, Deleter>&&>(),
  75     "unique_ptr<Derived, Deleter>::pointer not convertible to Derived*");