| // { dg-do compile { target c++11 } } |
| |
| // Copyright (C) 2012-2021 Free Software Foundation, Inc. |
| // |
| // This file is part of the GNU ISO C++ Library. This library is free |
| // software; you can redistribute it and/or modify it under the |
| // terms of the GNU General Public License as published by the |
| // Free Software Foundation; either version 3, or (at your option) |
| // any later version. |
| |
| // This library is distributed in the hope that it will be useful, |
| // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| // GNU General Public License for more details. |
| |
| // You should have received a copy of the GNU General Public License along |
| // with this library; see the file COPYING3. If not see |
| // <http://www.gnu.org/licenses/>. |
| |
| // Taken from N3436: |
| |
| #include <type_traits> |
| #include <string> |
| |
| struct eat { template<typename T> eat(T const &) {} }; |
| struct not_incrementable {}; |
| |
| struct inc { |
| template<typename T> |
| auto operator()(T t) const -> decltype(t++) |
| { return t++; } |
| }; |
| |
| template<typename A> |
| typename std::result_of<inc(A)>::type // sfinae here |
| try_inc(A a) { |
| return inc()(a); |
| } |
| |
| not_incrementable |
| try_inc(eat) { |
| return not_incrementable(); |
| } |
| |
| template<typename> |
| struct never { static const bool value = false; }; |
| |
| template<typename T> |
| struct Fail |
| { |
| static_assert(never<T>::value, "duh"); |
| typedef int type; |
| }; |
| |
| struct Fun |
| { |
| template<typename T> |
| typename Fail<T>::type operator()(T) |
| { return 0; } |
| }; |
| |
| template<typename T> |
| typename std::result_of<Fun(T)>::type foo(T) |
| { return 0; } |
| |
| template<typename> |
| int foo(...) |
| { return 0; } |
| |
| void result_of_sfinae() { |
| int x = try_inc(1); // OK |
| not_incrementable y = try_inc(std::string("foo")); // OK, not_incrementable |
| (void) x; |
| (void) y; |
| } |