[libc++] Implement LWG 2911 - add an is_aggregate type-trait

Summary:
This patch implements http://cplusplus.github.io/LWG/lwg-defects.html#2911.

I'm putting this up for review until __is_aggregate is added to clang (See D31513)

Reviewers: mclow.lists

Reviewed By: mclow.lists

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D31515

llvm-svn: 300126

1 files changed, 79 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_aggregate.pass.cpp b/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_aggregate.pass.cpp
new file mode 100644
index 00000000000..9c72d4d44ce
--- /dev/null
+++ b/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_aggregate.pass.cpp
@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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
+
+// <type_traits>
+
+// template <class T> struct is_aggregate;
+// template <class T> constexpr bool is_aggregate_v = is_aggregate<T>::value;
+
+#include <type_traits>
+#include "test_macros.h"
+
+template <class T>
+void test_true()
+{
+#if !defined(_LIBCPP_HAS_NO_IS_AGGREGATE)
+    static_assert( std::is_aggregate<T>::value, "");
+    static_assert( std::is_aggregate<const T>::value, "");
+    static_assert( std::is_aggregate<volatile T>::value, "");
+    static_assert( std::is_aggregate<const volatile T>::value, "");
+    static_assert( std::is_aggregate_v<T>, "");
+    static_assert( std::is_aggregate_v<const T>, "");
+    static_assert( std::is_aggregate_v<volatile T>, "");
+    static_assert( std::is_aggregate_v<const volatile T>, "");
+#endif
+}
+
+template <class T>
+void test_false()
+{
+#if !defined(_LIBCPP_HAS_NO_IS_AGGREGATE)
+    static_assert(!std::is_aggregate<T>::value, "");
+    static_assert(!std::is_aggregate<const T>::value, "");
+    static_assert(!std::is_aggregate<volatile T>::value, "");
+    static_assert(!std::is_aggregate<const volatile T>::value, "");
+    static_assert(!std::is_aggregate_v<T>, "");
+    static_assert(!std::is_aggregate_v<const T>, "");
+    static_assert(!std::is_aggregate_v<volatile T>, "");
+    static_assert(!std::is_aggregate_v<const volatile T>, "");
+#endif
+}
+
+struct Aggregate {};
+struct HasCons { HasCons(int); };
+struct HasPriv {
+  void PreventUnusedPrivateMemberWarning();
+private:
+  int x;
+};
+struct Union { int x; void* y; };
+
+
+int main ()
+{
+  {
+    test_false<void>();
+    test_false<int>();
+    test_false<void*>();
+    test_false<void()>();
+    test_false<void() const>();
+    test_false<void(Aggregate::*)(int) const>();
+    test_false<Aggregate&>();
+    test_false<HasCons>();
+    test_false<HasPriv>();
+  }
+  {
+    test_true<Aggregate>();
+    test_true<Aggregate[]>();
+    test_true<Aggregate[42][101]>();
+    test_true<Union>();
+  }
+}