1 //===----------------------------------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is dual licensed under the MIT and the University of Illinois Open 6 // Source Licenses. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 // UNSUPPORTED: c++98, c++03, c++11, c++14 11 12 // template <class T> constexpr add_const<T>& as_const(T& t) noexcept; // C++17 13 // template <class T> add_const<T>& as_const(const T&&) = delete; // C++17 14 15 #include <utility> 16 #include <cassert> 17 18 struct S {int i;}; 19 bool operator==(const S& x, const S& y) { return x.i == y.i; } 20 bool operator==(const volatile S& x, const volatile S& y) { return x.i == y.i; } 21 22 template<typename T> 23 void test(T& t) 24 { 25 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const (t))>::type>::value, ""); 26 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const< T>(t))>::type>::value, ""); 27 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const<const T>(t))>::type>::value, ""); 28 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const<volatile T>(t))>::type>::value, ""); 29 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const<const volatile T>(t))>::type>::value, ""); 30 31 assert(std::as_const(t) == t); 32 assert(std::as_const< T>(t) == t); 33 assert(std::as_const<const T>(t) == t); 34 assert(std::as_const<volatile T>(t) == t); 35 assert(std::as_const<const volatile T>(t) == t); 36 } 37 38 int main() 39 { 40 int i = 3; 41 double d = 4.0; 42 S s{2}; 43 test(i); 44 test(d); 45 test(s); 46 } 47
