Implement C++17 tuple bits. Including apply and make_from_tuple.

This patch upgrades <tuple> to be C++17 compliant by implementing:

* tuple_size_v: This was forgotten when implementing the other _v traits.
* std::apply: This was added via LFTS v1 in p0220r1.
* std::make_from_tuple: This was added in p0209r2.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@275745 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/tuple/tuple.tuple/tuple.apply/make_from_tuple.pass.cpp

@@ -0,0 +1,210 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <tuple>
+
+// template <class T, class Tuple> constexpr T make_from_tuple(Tuple&&);
+
+#include <tuple>
+#include <array>
+#include <utility>
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+#include "type_id.h"
+
+template <class Tuple>
+struct ConstexprConstructibleFromTuple {
+  template <class ...Args>
+  explicit constexpr ConstexprConstructibleFromTuple(Args&&... xargs)
+      : args{std::forward<Args>(xargs)...} {}
+  Tuple args;
+};
+
+template <class TupleLike>
+struct ConstructibleFromTuple;
+
+template <template <class ...> class Tuple, class ...Types>
+struct ConstructibleFromTuple<Tuple<Types...>> {
+  template <class ...Args>
+  explicit ConstructibleFromTuple(Args&&... xargs)
+      : args(xargs...),
+        arg_types(&makeArgumentID<Args&&...>())
+  {}
+  Tuple<std::decay_t<Types>...> args;
+  TypeID const* arg_types;
+};
+
+template <class Tp, size_t N>
+struct ConstructibleFromTuple<std::array<Tp, N>> {
+template <class ...Args>
+  explicit ConstructibleFromTuple(Args&&... xargs)
+      : args{xargs...},
+        arg_types(&makeArgumentID<Args&&...>())
+  {}
+  std::array<Tp, N> args;
+  TypeID const* arg_types;
+};
+
+template <class Tuple>
+constexpr bool do_constexpr_test(Tuple&& tup) {
+    using RawTuple = std::decay_t<Tuple>;
+    using Tp = ConstexprConstructibleFromTuple<RawTuple>;
+    return std::make_from_tuple<Tp>(std::forward<Tuple>(tup)).args == tup;
+}
+
+// Needed by do_forwarding_test() since it compare pairs of different types.
+template <class T1, class T2, class U1, class U2>
+inline bool operator==(const std::pair<T1, T2>& lhs, const std::pair<U1, U2>& rhs) {
+    return lhs.first == rhs.first && lhs.second == rhs.second;
+}
+
+template <class ...ExpectTypes, class Tuple>
+bool do_forwarding_test(Tuple&& tup) {
+    using RawTuple = std::decay_t<Tuple>;
+    using Tp = ConstructibleFromTuple<RawTuple>;
+    const Tp value = std::make_from_tuple<Tp>(std::forward<Tuple>(tup));
+    return value.args == tup
+        && value.arg_types == &makeArgumentID<ExpectTypes...>();
+}
+
+void test_constexpr_construction() {
+    {
+        constexpr std::tuple<> tup;
+        static_assert(do_constexpr_test(tup), "");
+    }
+    {
+        constexpr std::tuple<int> tup(42);
+        static_assert(do_constexpr_test(tup), "");
+    }
+    {
+        constexpr std::tuple<int, long, void*> tup(42, 101, nullptr);
+        static_assert(do_constexpr_test(tup), "");
+    }
+    {
+        constexpr std::pair<int, const char*> p(42, "hello world");
+        static_assert(do_constexpr_test(p), "");
+    }
+    {
+        using Tuple = std::array<int, 3>;
+        using ValueTp = ConstexprConstructibleFromTuple<Tuple>;
+        constexpr Tuple arr = {42, 101, -1};
+        constexpr ValueTp value = std::make_from_tuple<ValueTp>(arr);
+        static_assert(value.args[0] == arr[0] && value.args[1] == arr[1]
+            && value.args[2] == arr[2], "");
+    }
+}
+
+void test_perfect_forwarding() {
+    {
+        using Tup = std::tuple<>;
+        Tup tup;
+        Tup const& ctup = tup;
+        assert(do_forwarding_test<>(tup));
+        assert(do_forwarding_test<>(ctup));
+    }
+    {
+        using Tup = std::tuple<int>;
+        Tup tup(42);
+        Tup const& ctup = tup;
+        assert(do_forwarding_test<int&>(tup));
+        assert(do_forwarding_test<int const&>(ctup));
+        assert(do_forwarding_test<int&&>(std::move(tup)));
+        assert(do_forwarding_test<int const&&>(std::move(ctup)));
+    }
+    {
+        using Tup = std::tuple<int&, const char*, unsigned&&>;
+        int x = 42;
+        unsigned y = 101;
+        Tup tup(x, "hello world", std::move(y));
+        Tup const& ctup = tup;
+        assert((do_forwarding_test<int&, const char*&, unsigned&>(tup)));
+        assert((do_forwarding_test<int&, const char* const&, unsigned &>(ctup)));
+        assert((do_forwarding_test<int&, const char*&&, unsigned&&>(std::move(tup))));
+        assert((do_forwarding_test<int&, const char* const&&, unsigned &&>(std::move(ctup))));
+    }
+    // test with pair<T, U>
+    {
+        using Tup = std::pair<int&, const char*>;
+        int x = 42;
+        Tup tup(x, "hello world");
+        Tup const& ctup = tup;
+        assert((do_forwarding_test<int&, const char*&>(tup)));
+        assert((do_forwarding_test<int&, const char* const&>(ctup)));
+        assert((do_forwarding_test<int&, const char*&&>(std::move(tup))));
+        assert((do_forwarding_test<int&, const char* const&&>(std::move(ctup))));
+    }
+    // test with array<T, I>
+    {
+        using Tup = std::array<int, 3>;
+        Tup tup = {42, 101, -1};
+        Tup const& ctup = tup;
+        assert((do_forwarding_test<int&, int&, int&>(tup)));
+        assert((do_forwarding_test<int const&, int const&, int const&>(ctup)));
+        assert((do_forwarding_test<int&&, int&&, int&&>(std::move(tup))));
+        assert((do_forwarding_test<int const&&, int const&&, int const&&>(std::move(ctup))));
+    }
+}
+
+void test_noexcept() {
+    struct NothrowMoveable {
+      NothrowMoveable() = default;
+      NothrowMoveable(NothrowMoveable const&) {}
+      NothrowMoveable(NothrowMoveable&&) noexcept {}
+    };
+    struct TestType {
+      TestType(int, NothrowMoveable) noexcept {}
+      TestType(int, int, int) noexcept(false) {}
+      TestType(long, long, long) noexcept {}
+    };
+    {
+        using Tuple = std::tuple<int, NothrowMoveable>;
+        Tuple tup; ((void)tup);
+        Tuple const& ctup = tup; ((void)ctup);
+        ASSERT_NOT_NOEXCEPT(std::make_from_tuple<TestType>(ctup));
+        ASSERT_NOEXCEPT(std::make_from_tuple<TestType>(std::move(tup)));
+    }
+    {
+        using Tuple = std::pair<int, NothrowMoveable>;
+        Tuple tup; ((void)tup);
+        Tuple const& ctup = tup; ((void)ctup);
+        ASSERT_NOT_NOEXCEPT(std::make_from_tuple<TestType>(ctup));
+        ASSERT_NOEXCEPT(std::make_from_tuple<TestType>(std::move(tup)));
+    }
+    {
+        using Tuple = std::tuple<int, int, int>;
+        Tuple tup; ((void)tup);
+        ASSERT_NOT_NOEXCEPT(std::make_from_tuple<TestType>(tup));
+    }
+    {
+        using Tuple = std::tuple<long, long, long>;
+        Tuple tup; ((void)tup);
+        ASSERT_NOEXCEPT(std::make_from_tuple<TestType>(tup));
+    }
+    {
+        using Tuple = std::array<int, 3>;
+        Tuple tup; ((void)tup);
+        ASSERT_NOT_NOEXCEPT(std::make_from_tuple<TestType>(tup));
+    }
+    {
+        using Tuple = std::array<long, 3>;
+        Tuple tup; ((void)tup);
+        ASSERT_NOEXCEPT(std::make_from_tuple<TestType>(tup));
+    }
+}
+
+int main()
+{
+    test_constexpr_construction();
+    test_perfect_forwarding();
+    test_noexcept();
+}