Import libs 4 (#758)

3 files changed, 27 insertions, 5 deletions

diff --git a/library/cpp/threading/future/core/future-inl.h b/library/cpp/threading/future/core/future-inl.h
index a98175af2dc..db58b3156c9 100644
--- a/library/cpp/threading/future/core/future-inl.h
+++ b/library/cpp/threading/future/core/future-inl.h
@@ -729,16 +729,16 @@ namespace NThreading {
     }
 
     template <typename R>
-    inline TFuture<R> TFuture<void>::Return(const R& value) const {
-        auto promise = NewPromise<R>();
-        Subscribe([=](const TFuture<void>& future) mutable {
+    inline TFuture<std::remove_cvref_t<R>> TFuture<void>::Return(R&& value) const {
+        auto promise = NewPromise<std::remove_cvref_t<R>>();
+        Subscribe([promise, value = std::forward<R>(value)](const TFuture<void>& future) mutable {
             try {
                 future.TryRethrow();
             } catch (...) {
                 promise.SetException(std::current_exception());
                 return;
             }
-            promise.SetValue(value);
+            promise.SetValue(std::move(value));
         });
         return promise;
     }
diff --git a/library/cpp/threading/future/core/future.h b/library/cpp/threading/future/core/future.h
index c803b28b756..598336282a0 100644
--- a/library/cpp/threading/future/core/future.h
+++ b/library/cpp/threading/future/core/future.h
@@ -169,7 +169,7 @@ namespace NThreading {
         TFuture<TFutureType<TFutureCallResult<F, void>>> Apply(F&& func) const;
 
         template <typename R>
-        TFuture<R> Return(const R& value) const;
+        TFuture<std::remove_cvref_t<R>> Return(R&& value) const;
 
         TFuture<void> IgnoreResult() const {
             return *this;
diff --git a/library/cpp/threading/future/future_ut.cpp b/library/cpp/threading/future/future_ut.cpp
index 05950a568d4..26f8fa9e9c3 100644
--- a/library/cpp/threading/future/future_ut.cpp
+++ b/library/cpp/threading/future/future_ut.cpp
@@ -635,6 +635,28 @@ namespace {
             TestApplyLvalueCopyImpl<void>();
             TestApplyLvalueCopyImpl<int>();
         }
+
+        Y_UNIT_TEST(ReturnForwardingTypeDeduction) {
+            const TString e = TString(80, 'a');
+            TString l = TString(80, 'a');
+
+            TFuture<TString> futureL = MakeFuture().Return(l);
+            UNIT_ASSERT_VALUES_EQUAL(futureL.GetValue(), e);
+            UNIT_ASSERT_VALUES_EQUAL(l, e);
+
+            TFuture<TString> futureR = MakeFuture().Return(std::move(l));
+            UNIT_ASSERT_VALUES_EQUAL(futureR.GetValue(), e);
+        }
+
+        Y_UNIT_TEST(ReturnForwardingCopiesCount) {
+            size_t numCopies = 0;
+            TCopyCounter copyCounter(&numCopies);
+
+            auto returnedCounter = MakeFuture().Return(std::move(copyCounter)).ExtractValueSync();
+            Y_DO_NOT_OPTIMIZE_AWAY(returnedCounter);
+
+            UNIT_ASSERT_VALUES_EQUAL(numCopies, 0);
+        }
     }
 
 }