[PATCH] libstdc++: Add test for std::con/disjunction's base class

[Patrick Palka <ppalka@redhat.com>]

Tested on x86_64-pc-linux-gnu, does this look OK for trunk?

libstdc++-v3/ChangeLog:

	* testsuite/20_util/logical_traits/requirements/base_classes.cc: New test.
---
 .../requirements/base_classes.cc              | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 libstdc++-v3/testsuite/20_util/logical_traits/requirements/base_classes.cc

diff --git a/libstdc++-v3/testsuite/20_util/logical_traits/requirements/base_classes.cc b/libstdc++-v3/testsuite/20_util/logical_traits/requirements/base_classes.cc
new file mode 100644
index 00000000000..6699037bb14
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/logical_traits/requirements/base_classes.cc
@@ -0,0 +1,37 @@
+// { dg-do compile { target c++17 } }
+
+#include <utility>
+
+using std::true_type;
+using std::false_type;
+
+template<int> struct T : std::true_type { };
+template<int> struct F : std::false_type { };
+
+// [meta.logical]/5: The specialization conjunction<B_1, ..., B_n> has a
+// public and unambiguous base that is either:
+//   - the first type B_i in the list true_type, B_1, ..., B_n for which
+//       bool(B_i::value) is false, or
+//   - if there is no such Bi, the last type in the list.
+
+static_assert(std::is_base_of_v<true_type, std::conjunction<>>);
+static_assert(std::is_base_of_v<T<0>, std::conjunction<T<0>>>);
+static_assert(std::is_base_of_v<F<0>, std::conjunction<F<0>>>);
+static_assert(std::is_base_of_v<T<1>, std::conjunction<T<0>, T<1>>>);
+static_assert(std::is_base_of_v<F<0>, std::conjunction<F<0>, F<1>>>);
+static_assert(std::is_base_of_v<F<0>, std::conjunction<T<0>, F<0>, F<1>>>);
+static_assert(std::is_base_of_v<F<0>, std::conjunction<T<0>, F<0>, T<1>, F<1>>>);
+
+// [meta.logical]/10: The specialization disjunction<B_1, ..., B_n> has a
+// public and unambiguous base that is either:
+//   - the first type B_i in the list false_type, B_1, ..., B_n for which
+//       bool(B_i::value) is true, or
+//   - if there is no such Bi, the last type in the list.
+
+static_assert(std::is_base_of_v<false_type, std::disjunction<>>);
+static_assert(std::is_base_of_v<T<0>, std::disjunction<T<0>>>);
+static_assert(std::is_base_of_v<F<0>, std::disjunction<F<0>>>);
+static_assert(std::is_base_of_v<T<0>, std::disjunction<T<0>, T<1>>>);
+static_assert(std::is_base_of_v<F<1>, std::disjunction<F<0>, F<1>>>);
+static_assert(std::is_base_of_v<T<0>, std::disjunction<T<0>, F<0>, F<1>>>);
+static_assert(std::is_base_of_v<T<0>, std::disjunction<T<0>, F<0>, T<1>, F<1>>>);
-- 
2.37.2.382.g795ea8776b