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Re-implement LWG 2770 - Fix tuple_size with structured bindings.

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This patch implements the correct PR for LWG 2770. It also makes the primary
tuple_size template incomplete again which fixes part of llvm.org/PR31513.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@290846 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Fiselier
2017-01-02 23:54:13 +00:00
parent b45121da64
commit 408438494b
5 changed files with 34 additions and 29 deletions
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21
include/__tuple
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@@ -22,19 +22,32 @@
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY tuple_size {};
template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY tuple_size;
struct __empty_tuple_size_base {};
template <class _Tp, class = void>
struct __tuple_size_base_type {
typedef __empty_tuple_size_base type;
};
template <class _Tp>
struct __tuple_size_base_type<_Tp, typename __void_t<decltype(tuple_size<_Tp>::value)>::type>
{
typedef integral_constant<size_t, tuple_size<_Tp>::value> type;
};
template <class _Tp>
class _LIBCPP_TYPE_VIS_ONLY tuple_size<const _Tp>
: public tuple_size<_Tp> {};
: public __tuple_size_base_type<_Tp>::type {};
template <class _Tp>
class _LIBCPP_TYPE_VIS_ONLY tuple_size<volatile _Tp>
: public tuple_size<_Tp> {};
: public __tuple_size_base_type<_Tp>::type {};
template <class _Tp>
class _LIBCPP_TYPE_VIS_ONLY tuple_size<const volatile _Tp>
: public tuple_size<_Tp> {};
: public __tuple_size_base_type<_Tp>::type {};
template <size_t _Ip, class _Tp> class _LIBCPP_TYPE_VIS_ONLY tuple_element;

2
include/tuple
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@@ -84,7 +84,7 @@ template <class T, class Tuple>
constexpr T make_from_tuple(Tuple&& t); // C++17
// 20.4.1.4, tuple helper classes:
template <class T> class tuple_size;
template <class T> class tuple_size; // undefined
template <class... T> class tuple_size<tuple<T...>>;
template <class T>
constexpr size_t tuple_size_v = tuple_size<T>::value; // C++17

6
test/std/utilities/tuple/tuple.tuple/tuple.helper/tuple_size.fail.cpp
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@@ -21,7 +21,7 @@
int main()
{
(void)std::tuple_size<std::tuple<> &>::value; // expected-error {{no member named 'value'}}
(void)std::tuple_size<int>::value; // expected-error {{no member named 'value'}}
(void)std::tuple_size<std::tuple<>*>::value; // expected-error {{no member named 'value'}}
(void)std::tuple_size<std::tuple<> &>::value; // expected-error {{implicit instantiation of undefined template}}
(void)std::tuple_size<int>::value; // expected-error {{implicit instantiation of undefined template}}
(void)std::tuple_size<std::tuple<>*>::value; // expected-error {{implicit instantiation of undefined template}}
}

32
test/std/utilities/tuple/tuple.tuple/tuple.helper/tuple_size.pass.cpp
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@@ -18,8 +18,6 @@
// UNSUPPORTED: c++98, c++03
#include <tuple>
#include <utility>
#include <array>
#include <type_traits>
template <class T, class = decltype(std::tuple_size<T>::value)>
@@ -27,27 +25,29 @@ constexpr bool has_value(int) { return true; }
template <class> constexpr bool has_value(long) { return false; }
template <class T> constexpr bool has_value() { return has_value<T>(0); }
struct Dummy {};
template <class T, std::size_t N>
void test()
{
static_assert(has_value<T>(), "");
static_assert((std::is_base_of<std::integral_constant<std::size_t, N>,
std::tuple_size<T> >::value), "");
static_assert(has_value<const T>(), "");
static_assert((std::is_base_of<std::integral_constant<std::size_t, N>,
std::tuple_size<const T> >::value), "");
static_assert(has_value<volatile T>(), "");
static_assert((std::is_base_of<std::integral_constant<std::size_t, N>,
std::tuple_size<volatile T> >::value), "");
static_assert(has_value<const volatile T>(), "");
static_assert((std::is_base_of<std::integral_constant<std::size_t, N>,
std::tuple_size<const volatile T> >::value), "");
{
static_assert(!has_value<T &>(), "");
static_assert(!has_value<T *>(), "");
}
}
void test_tuple_size_value_sfinae() {
// Test that the ::value member does not exist
static_assert(has_value<std::tuple<int> const>(), "");
static_assert(has_value<std::pair<int, long> volatile>(), "");
static_assert(!has_value<int>(), "");
static_assert(!has_value<const int>(), "");
static_assert(!has_value<volatile void>(), "");
static_assert(!has_value<const volatile std::tuple<int>&>(), "");
}
int main()
@@ -56,13 +56,5 @@ int main()
test<std::tuple<int>, 1>();
test<std::tuple<char, int>, 2>();
test<std::tuple<char, char*, int>, 3>();
test<std::pair<int, void*>, 2>();
test<std::array<int, 42>, 42>();
{
static_assert(!has_value<void>(), "");
static_assert(!has_value<void*>(), "");
static_assert(!has_value<int>(), "");
static_assert(!has_value<std::pair<int, int>*>(), "");
static_assert(!has_value<std::array<int, 42>&>(), "");
}
test_tuple_size_value_sfinae();
}

2
test/std/utilities/tuple/tuple.tuple/tuple.helper/tuple_size_v.fail.cpp
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@@ -22,5 +22,5 @@ int main()
(void)std::tuple_size_v<std::tuple<> &>; // expected-note {{requested here}}
(void)std::tuple_size_v<int>; // expected-note {{requested here}}
(void)std::tuple_size_v<std::tuple<>*>; // expected-note {{requested here}}
// expected-error@tuple:* 3 {{no member named 'value'}}
// expected-error@tuple:* 3 {{implicit instantiation of undefined template}}
}