[libcxx] Reorganize tests since the application of P0602R4

Summary:
P0602R4 makes the special member functions of optional and variant
conditionally trivial based on the types in the optional/variant.
We already implemented that, but the tests were organized as if this
were a non-standard extension. This patch reorganizes the tests in a
way that makes more sense since this is not an extension anymore.

Reviewers: EricWF, mpark, mclow.lists

Subscribers: christof, jkorous, dexonsmith, libcxx-commits

Differential Revision: https://reviews.llvm.org/D54772

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@350884 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/utilities/optional/optional.object/triviality.abi.pass.cpp

@@ -0,0 +1,98 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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
+
+// <optional>
+
+// This test asserts the triviality of special member functions of optional<T>
+// whenever T has these special member functions trivial. The goal of this test
+// is to make sure that we do not change the triviality of those, since that
+// constitues an ABI break (small enough optionals would be passed by registers).
+//
+// constexpr optional(const optional& rhs);
+// constexpr optional(optional&& rhs) noexcept(see below);
+// constexpr optional<T>& operator=(const optional& rhs);
+// constexpr optional<T>& operator=(optional&& rhs) noexcept(see below);
+
+#include <optional>
+#include <type_traits>
+#include <cassert>
+
+#include "archetypes.hpp"
+
+template <class T>
+struct SpecialMemberTest {
+    using O = std::optional<T>;
+
+    static_assert(std::is_trivially_destructible_v<O> ==
+        std::is_trivially_destructible_v<T>,
+        "optional<T> is trivially destructible if and only if T is.");
+
+    static_assert(std::is_trivially_copy_constructible_v<O> ==
+        std::is_trivially_copy_constructible_v<T>,
+        "optional<T> is trivially copy constructible if and only if T is.");
+
+    static_assert(std::is_trivially_move_constructible_v<O> ==
+        std::is_trivially_move_constructible_v<T> ||
+        (!std::is_move_constructible_v<T> && std::is_trivially_copy_constructible_v<T>),
+        "optional<T> is trivially move constructible if T is trivially move constructible, "
+        "or if T is trivially copy constructible and is not move constructible.");
+
+    static_assert(std::is_trivially_copy_assignable_v<O> ==
+        (std::is_trivially_destructible_v<T> &&
+         std::is_trivially_copy_constructible_v<T> &&
+         std::is_trivially_copy_assignable_v<T>),
+        "optional<T> is trivially copy assignable if and only if T is trivially destructible, "
+        "trivially copy constructible, and trivially copy assignable.");
+
+    static_assert(std::is_trivially_move_assignable_v<O> ==
+        (std::is_trivially_destructible_v<T> &&
+         ((std::is_trivially_move_constructible_v<T> && std::is_trivially_move_assignable_v<T>) ||
+          ((!std::is_move_constructible_v<T> || !std::is_move_assignable_v<T>) &&
+           std::is_trivially_copy_constructible_v<T> && std::is_trivially_copy_assignable_v<T>))),
+        "optional<T> is trivially move assignable if T is trivially destructible, and either "
+        "(1) trivially move constructible and trivially move assignable, or "
+        "(2) not move constructible or not move assignable, and "
+        "trivially copy constructible and trivially copy assignable.");
+};
+
+template <class ...Args> static void sink(Args&&...) {}
+
+template <class ...TestTypes>
+struct DoTestsMetafunction {
+    DoTestsMetafunction() { sink(SpecialMemberTest<TestTypes>{}...); }
+};
+
+struct TrivialMoveNonTrivialCopy {
+    TrivialMoveNonTrivialCopy() = default;
+    TrivialMoveNonTrivialCopy(const TrivialMoveNonTrivialCopy&) {}
+    TrivialMoveNonTrivialCopy(TrivialMoveNonTrivialCopy&&) = default;
+    TrivialMoveNonTrivialCopy& operator=(const TrivialMoveNonTrivialCopy&) { return *this; }
+    TrivialMoveNonTrivialCopy& operator=(TrivialMoveNonTrivialCopy&&) = default;
+};
+
+struct TrivialCopyNonTrivialMove {
+    TrivialCopyNonTrivialMove() = default;
+    TrivialCopyNonTrivialMove(const TrivialCopyNonTrivialMove&) = default;
+    TrivialCopyNonTrivialMove(TrivialCopyNonTrivialMove&&) {}
+    TrivialCopyNonTrivialMove& operator=(const TrivialCopyNonTrivialMove&) = default;
+    TrivialCopyNonTrivialMove& operator=(TrivialCopyNonTrivialMove&&) { return *this; }
+};
+
+int main()
+{
+    sink(
+        ImplicitTypes::ApplyTypes<DoTestsMetafunction>{},
+        ExplicitTypes::ApplyTypes<DoTestsMetafunction>{},
+        NonLiteralTypes::ApplyTypes<DoTestsMetafunction>{},
+        NonTrivialTypes::ApplyTypes<DoTestsMetafunction>{},
+        DoTestsMetafunction<TrivialMoveNonTrivialCopy, TrivialCopyNonTrivialMove>{}
+    );
+}