Export of internal Abseil changes.

--
dabd5614eec687a27bcba28e1d98e84ce716f281 by Abseil Team <absl-team@google.com>:

Demonstrate that std::bitset is supported by AbslHash, both with a comment and
a test.

PiperOrigin-RevId: 218782040
GitOrigin-RevId: dabd5614eec687a27bcba28e1d98e84ce716f281
Change-Id: I777d5e030ba8c6b8a2a353e29ace87484caa811f

1 files changed, 9 insertions, 0 deletions

diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h
index 4543d679..b66cc1b5 100644
--- a/absl/hash/internal/hash.h
+++ b/absl/hash/internal/hash.h
@@ -494,6 +494,15 @@ AbslHashValue(H hash_state, const absl::variant<T...>& v) {
   }
   return H::combine(std::move(hash_state), v.index());
 }
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Other Types
+// -----------------------------------------------------------------------------
+
+// AbslHashValue for hashing std::bitset is not defined, for the same reason as
+// for vector<bool> (see std::vector above): It does not expose the raw bytes,
+// and a fallback to std::hash<> is most likely faster.
+
 // -----------------------------------------------------------------------------
 
 // hash_range_or_bytes()