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PR libstdc++/89102 fix common_type<> and common_type<T> specializations 

This is a partial implementation of the revised std::common_type rules
from P0435R1.

	PR libstdc++/89102 (partial)
	* include/std/type_traits (common_type<>): Define.
	(common_type<T>): Derive from common_type<T, T>.
	* testsuite/20_util/common_type/requirements/explicit_instantiation.cc:
	Test zero-length template argument list.
	* testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc:
	Test additional single argument cases.
	* testsuite/20_util/common_type/requirements/sfinae_friendly_2.cc:
	Adjust expected error.

From-SVN: r268586
This commit is contained in:
Jonathan Wakely 2019-02-06 17:25:26 +00:00 committed by Jonathan Wakely
parent 12f82acc9e
commit 373c726ec6
5 changed files with 33 additions and 2 deletions
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12
libstdc++-v3/ChangeLog
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@ -1,3 +1,15 @@
2019-02-06 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/89102 (partial)
* include/std/type_traits (common_type<>): Define.
(common_type<T>): Derive from common_type<T, T>.
* testsuite/20_util/common_type/requirements/explicit_instantiation.cc:
Test zero-length template argument list.
* testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc:
Test additional single argument cases.
* testsuite/20_util/common_type/requirements/sfinae_friendly_2.cc:
Adjust expected error.
2019-02-05 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/89128

7
libstdc++-v3/include/std/type_traits
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@ -2132,9 +2132,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct __expanded_common_type_wrapper<__failure_type, _Args...>
{ typedef __failure_type type; };
template<>
struct common_type<>
{ };
template<typename _Tp>
struct common_type<_Tp>
{ typedef typename decay<_Tp>::type type; };
: common_type<_Tp, _Tp>
{ };
template<typename _Tp, typename _Up>
struct common_type<_Tp, _Up>

1
libstdc++-v3/testsuite/20_util/common_type/requirements/explicit_instantiation.cc
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@ -30,6 +30,7 @@ namespace std
typedef void test_type5;
typedef const void test_type6;
template struct common_type<>;
template struct common_type<test_type1>;
template struct common_type<test_type1, test_type2>;
template struct common_type<test_type1, test_type2, test_type3>;

13
libstdc++-v3/testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc
View File

@ -159,7 +159,10 @@ namespace std {
};
}
static_assert(is_type<std::common_type<int>, int>(), "");
static_assert(is_type<std::common_type<const int>, int>(), "");
static_assert(is_type<std::common_type<int, int>, int>(), "");
static_assert(is_type<std::common_type<const int, int>, int>(), "");
static_assert(is_type<std::common_type<ScEn, ScEn>, ScEn>(), "");
static_assert(is_type<std::common_type<UnscEn, UnscEn>, UnscEn>(), "");
static_assert(is_type<std::common_type<UnscEn, int>, int>(), "");
@ -180,6 +183,8 @@ static_assert(is_type<std::common_type<int*, const volatile int*>,
const volatile int*>(), "");
static_assert(is_type<std::common_type<void*, const volatile int*>,
const volatile void*>(), "");
static_assert(is_type<std::common_type<void>, void>(), "");
static_assert(is_type<std::common_type<const void>, void>(), "");
static_assert(is_type<std::common_type<void, void>, void>(), "");
static_assert(is_type<std::common_type<const void, const void>, void>(), "");
static_assert(is_type<std::common_type<int&, int&&>, int>(), "");
@ -316,6 +321,14 @@ static_assert(!has_type<std::common_type<UConv1, Abstract&&>>(), "");
static_assert(!has_type<std::common_type<std::initializer_list<int>,
std::initializer_list<long>>>(), "");
// PR libstdc++/89102
static_assert(!has_type<std::common_type<int() &>>(), "");
static_assert(!has_type<std::common_type<int() & noexcept>>(), "");
static_assert(!has_type<std::common_type<int() const>>(), "");
static_assert(!has_type<std::common_type<int(...) &>>(), "");
static_assert(!has_type<std::common_type<int(...) & noexcept>>(), "");
static_assert(!has_type<std::common_type<int(...) const>>(), "");
void test(int i)
{
auto local_lmd1 = [=](int, double) { return i + i; };

2
libstdc++-v3/testsuite/20_util/common_type/requirements/sfinae_friendly_2.cc
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@ -25,7 +25,7 @@ template<typename... Args>
constexpr
std::array<typename std::common_type<Args...>::type,
sizeof...(Args)>
make_array(Args&&... args) // { dg-error "invalid use" }
make_array(Args&&... args) // { dg-error "no type.*common_type<>" }
{
typedef typename std::common_type<Args...>::type CT;
return std::array<CT, sizeof...(Args)>{static_cast<CT>