From 62cf6a70414e15b356ec4f712ca8758133674f28 Mon Sep 17 00:00:00 2001
From: Abseil Team <absl-team@google.com>
Date: Fri, 15 May 2020 08:23:25 -0700
Subject: Export of internal Abseil changes

--
dc36565216b3022abb5a3c92f46fb4079bda869e by Samuel Benzaquen <sbenza@google.com>:

Add support for std::reference_wrapper to absl::Hash.

PiperOrigin-RevId: 311733171
GitOrigin-RevId: dc36565216b3022abb5a3c92f46fb4079bda869e
Change-Id: I74543390446c2b7f6d856935aa36f28539810eef
---
 absl/hash/hash_test.cc    | 18 ++++++++++++++++++
 absl/hash/internal/hash.h |  7 +++++++
 2 files changed, 25 insertions(+)

(limited to 'absl')

diff --git a/absl/hash/hash_test.cc b/absl/hash/hash_test.cc
index b38d46d47dd3..39ba24a85afb 100644
--- a/absl/hash/hash_test.cc
+++ b/absl/hash/hash_test.cc
@@ -581,6 +581,24 @@ TEST(HashValueTest, Maps) {
       MM{{1, "foo"}, {1, "foo"}, {43, "bar"}}, MM{{1, "foo"}, {43, "baz"}})));
 }
 
+TEST(HashValueTest, ReferenceWrapper) {
+  EXPECT_TRUE(is_hashable<std::reference_wrapper<Private>>::value);
+
+  Private p1{1}, p10{10};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      p1, p10, std::ref(p1), std::ref(p10), std::cref(p1), std::cref(p10))));
+
+  EXPECT_TRUE(is_hashable<std::reference_wrapper<int>>::value);
+  int one = 1, ten = 10;
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      one, ten, std::ref(one), std::ref(ten), std::cref(one), std::cref(ten))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::tuple<std::reference_wrapper<int>>(std::ref(one)),
+                      std::tuple<std::reference_wrapper<int>>(std::ref(ten)),
+                      std::tuple<int>(one), std::tuple<int>(ten))));
+}
+
 template <typename T, typename = void>
 struct IsHashCallable : std::false_type {};
 
diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h
index a71bd4a65df8..9e608f7c3c29 100644
--- a/absl/hash/internal/hash.h
+++ b/absl/hash/internal/hash.h
@@ -551,6 +551,13 @@ typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue(
 // AbslHashValue for Wrapper Types
 // -----------------------------------------------------------------------------
 
+// AbslHashValue for hashing std::reference_wrapper
+template <typename H, typename T>
+typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue(
+    H hash_state, std::reference_wrapper<T> opt) {
+  return H::combine(std::move(hash_state), opt.get());
+}
+
 // AbslHashValue for hashing absl::optional
 template <typename H, typename T>
 typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue(
-- 
cgit 1.4.1