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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// <utility>
// template <class T1, class T2> struct pair
// Test the SFINAE required by LWG Issue #2367.
// is_default_constructible<pair>
// UNSUPPORTED: c++03
#include <utility>
#include <type_traits>
#include <cassert>
#include "test_macros.h"
#if TEST_STD_VER > 11
#define CONSTEXPR_CXX14 constexpr
#define STATIC_ASSERT_CXX14(Pred) static_assert(Pred, "")
#else
#define CONSTEXPR_CXX14
#define STATIC_ASSERT_CXX14(Pred) assert(Pred)
#endif
struct DeletedDefault {
// A class with a deleted default constructor. Used to test the SFINAE
// on std::pair's default constructor.
constexpr explicit DeletedDefault(int x) : value(x) {}
constexpr DeletedDefault() = delete;
int value;
};
template <class Tp, bool>
struct DependantType: public Tp {};
template <class T, bool Val>
using DependantIsDefault = DependantType<std::is_default_constructible<T>, Val>;
template <class T>
struct DefaultSFINAES {
template <bool Dummy = false, class = typename std::enable_if<
DependantIsDefault<T, Dummy>::value
>::type
>
constexpr DefaultSFINAES() : value() {}
constexpr explicit DefaultSFINAES(T const& x) : value(x) {}
T value;
};
struct NoDefault {
constexpr NoDefault(int v) : value(v) {}
int value;
};
template <class Tp>
void test_not_is_default_constructible()
{
{
typedef std::pair<int, Tp> P;
static_assert(!std::is_default_constructible<P>::value, "");
static_assert(std::is_constructible<P, int, Tp>::value, "");
}
{
typedef std::pair<Tp, int> P;
static_assert(!std::is_default_constructible<P>::value, "");
static_assert(std::is_constructible<P, Tp, int>::value, "");
}
{
typedef std::pair<Tp, Tp> P;
static_assert(!std::is_default_constructible<P>::value, "");
static_assert(std::is_constructible<P, Tp, Tp>::value, "");
}
}
template <class Tp>
void test_is_default_constructible()
{
{
typedef std::pair<int, Tp> P;
static_assert(std::is_default_constructible<P>::value, "");
}
{
typedef std::pair<Tp, int> P;
static_assert(std::is_default_constructible<P>::value, "");
}
{
typedef std::pair<Tp, Tp> P;
static_assert(std::is_default_constructible<P>::value, "");
}
}
template <class T>
struct IllFormedDefaultImp {
constexpr explicit IllFormedDefaultImp(int v) : value(v) {}
constexpr IllFormedDefaultImp() : value(T::DoesNotExistAndShouldNotCompile) {}
int value;
};
typedef IllFormedDefaultImp<int> IllFormedDefault;
// A class which provides a constexpr default constructor with a valid
// signature but an ill-formed body. The A compile error will be emitted if
// the default constructor is instantiated.
// Check that the SFINAE on the default constructor is not evaluated when
// it isn't needed. If the default constructor of 'IllFormedDefault' is evaluated
// in C++11, even with is_default_constructible, then this test should fail to
// compile. In C++14 and greater evaluate each test is evaluated as a constant
// expression.
// See LWG issue #2367
void test_illformed_default()
{
{
typedef std::pair<IllFormedDefault, int> P;
static_assert((std::is_constructible<P, IllFormedDefault, int>::value), "");
CONSTEXPR_CXX14 P p(IllFormedDefault(42), -5);
STATIC_ASSERT_CXX14(p.first.value == 42 && p.second == -5);
}
{
typedef std::pair<int, IllFormedDefault> P;
static_assert((std::is_constructible<P, int, IllFormedDefault>::value), "");
CONSTEXPR_CXX14 IllFormedDefault dd(-5);
CONSTEXPR_CXX14 P p(42, dd);
STATIC_ASSERT_CXX14(p.first == 42 && p.second.value == -5);
}
{
typedef std::pair<IllFormedDefault, IllFormedDefault> P;
static_assert((std::is_constructible<P, IllFormedDefault, IllFormedDefault>::value), "");
CONSTEXPR_CXX14 P p(IllFormedDefault(42), IllFormedDefault(-5));
STATIC_ASSERT_CXX14(p.first.value == 42 && p.second.value == -5);
}
}
int main(int, char**)
{
{
// Check that pair<T, U> can still be used even if
// is_default_constructible<T> or is_default_constructible<U> cause
// a compilation error.
test_illformed_default();
}
{
// pair::pair() is only disable in C++11 and beyond.
test_not_is_default_constructible<NoDefault>();
test_not_is_default_constructible<DeletedDefault>();
test_not_is_default_constructible<DefaultSFINAES<int&>>();
test_not_is_default_constructible<DefaultSFINAES<int&&>>();
test_not_is_default_constructible<int&>();
test_not_is_default_constructible<int&&>();
}
{
test_is_default_constructible<int>();
test_is_default_constructible<DefaultSFINAES<int>>();
}
return 0;
}
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