inlined_vector: fix incorrect conditions for move constructor fast paths.

These have nothing to do with copy construction or copy assignment, and using
"is trivially copy constructible" can in theory even give the wrong result if
the copy constructor is trivial but the move constructor is not.

PiperOrigin-RevId: 520488816
Change-Id: I6da4d57f3ce23b03044e0bf9aa70a14b51651fa3

1 files changed, 14 insertions, 10 deletions

diff --git a/absl/container/internal/inlined_vector.h b/absl/container/internal/inlined_vector.h
index 6397db48..4e628424 100644
--- a/absl/container/internal/inlined_vector.h
+++ b/absl/container/internal/inlined_vector.h
@@ -510,16 +510,20 @@ class Storage {
     //
     //  *  It's possible to trivially copy construct/assign the elements.
     //
-    // TODO(b/274984172): the conditions here, preserved from historical ones,
-    // don't actually implement this. They are far too conservative (they don't
-    // work for move-only types, and require both copyability and
-    // assignability).
-    ABSL_HARDENING_ASSERT(
-        other_storage.GetIsAllocated() ||
-        (std::is_same<A, std::allocator<ValueType<A>>>::value &&
-         absl::is_trivially_copy_constructible<ValueType<A>>::value &&
-         absl::is_trivially_copy_assignable<ValueType<A>>::value &&
-         absl::is_trivially_destructible<ValueType<A>>::value));
+    {
+      using V = ValueType<A>;
+      ABSL_HARDENING_ASSERT(
+          other_storage.GetIsAllocated() ||
+          (std::is_same<A, std::allocator<V>>::value &&
+           (
+               // First case above
+               ((absl::is_trivially_move_constructible<V>::value ||
+                 absl::is_trivially_move_assignable<V>::value) &&
+                absl::is_trivially_destructible<V>::value) ||
+               // Second case above
+               (absl::is_trivially_copy_constructible<V>::value ||
+                absl::is_trivially_copy_assignable<V>::value))));
+    }
 
     GetSizeAndIsAllocated() = other_storage.GetSizeAndIsAllocated();
     data_ = other_storage.data_;