Make `FlatHashMapPolicy` return `std::true_type` for relocatable objects.

This reduces produced binary size and can trigger even more optimizations in the future.

PiperOrigin-RevId: 584136517
Change-Id: I3854833799f88f28b755ec53132925f0c3d468ab

1 files changed, 30 insertions, 2 deletions

diff --git a/absl/container/internal/container_memory_test.cc b/absl/container/internal/container_memory_test.cc
index fb9c4dde..c1e57834 100644
--- a/absl/container/internal/container_memory_test.cc
+++ b/absl/container/internal/container_memory_test.cc
@@ -14,8 +14,11 @@
 
 #include "absl/container/internal/container_memory.h"
 
+#include <cstddef>
 #include <cstdint>
+#include <memory>
 #include <tuple>
+#include <type_traits>
 #include <typeindex>
 #include <typeinfo>
 #include <utility>
@@ -23,6 +26,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/container/internal/test_instance_tracker.h"
+#include "absl/meta/type_traits.h"
 #include "absl/strings/string_view.h"
 
 namespace absl {
@@ -219,8 +223,7 @@ TEST(DecomposePair, NotDecomposable) {
     ADD_FAILURE() << "Must not be called";
     return 'A';
   };
-  EXPECT_STREQ("not decomposable",
-               TryDecomposePair(f));
+  EXPECT_STREQ("not decomposable", TryDecomposePair(f));
   EXPECT_STREQ("not decomposable",
                TryDecomposePair(f, std::piecewise_construct, std::make_tuple(),
                                 std::make_tuple(0.5)));
@@ -251,6 +254,31 @@ TEST(MapSlotPolicy, ConstKeyAndValue) {
   EXPECT_EQ(tracker.copies(), 0);
 }
 
+TEST(MapSlotPolicy, TransferReturnsTrue) {
+  {
+    using slot_policy = map_slot_policy<int, float>;
+    EXPECT_TRUE(
+        (std::is_same<decltype(slot_policy::transfer<std::allocator<char>>(
+                          nullptr, nullptr, nullptr)),
+                      std::true_type>::value));
+  }
+  {
+    struct NonRelocatable {
+      NonRelocatable() = default;
+      NonRelocatable(NonRelocatable&&) {}
+      NonRelocatable& operator=(NonRelocatable&&) { return *this; }
+      void* self = nullptr;
+    };
+
+    EXPECT_FALSE(absl::is_trivially_relocatable<NonRelocatable>::value);
+    using slot_policy = map_slot_policy<int, NonRelocatable>;
+    EXPECT_TRUE(
+        (std::is_same<decltype(slot_policy::transfer<std::allocator<char>>(
+                          nullptr, nullptr, nullptr)),
+                      std::false_type>::value));
+  }
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END