Make variant's index part of the hash value

llvm-svn: 288554

1 files changed, 13 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/variant/variant.hash/hash.pass.cpp b/libcxx/test/std/utilities/variant/variant.hash/hash.pass.cpp
index 17455081300..d807a7c7e2e 100644
--- a/libcxx/test/std/utilities/variant/variant.hash/hash.pass.cpp
+++ b/libcxx/test/std/utilities/variant/variant.hash/hash.pass.cpp
@@ -105,7 +105,20 @@ void test_hash_monostate() {
   }
 }
 
+void test_hash_variant_duplicate_elements() {
+    // Test that the index of the alternative participates in the hash value.
+    using V = std::variant<std::monostate, std::monostate>;
+    using H = std::hash<V>;
+    H h{};
+    const V v1(std::in_place_index<0>);
+    const V v2(std::in_place_index<1>);
+    assert(h(v1) == h(v1));
+    assert(h(v2) == h(v2));
+    LIBCPP_ASSERT(h(v1) != h(v2));
+}
+
 int main() {
   test_hash_variant();
+  test_hash_variant_duplicate_elements();
   test_hash_monostate();
 }