From 109334de27c41273089c81ff20bae938ef763f23 Mon Sep 17 00:00:00 2001
From: Andrii Grynenko <andrii@fb.com>
Date: Mon, 12 Sep 2016 17:53:09 -0700
Subject: [PATCH] Fix TLObserver copy constructor

Reviewed By: yfeldblum

Differential Revision: D3853494

fbshipit-source-id: 23f5cadcb55a9307fb2a825fe4c53a03c5978d12
---
 folly/experimental/observer/Observer-inl.h        |  4 ++++
 folly/experimental/observer/Observer.h            |  1 +
 folly/experimental/observer/test/ObserverTest.cpp | 12 ++++++++++++
 3 files changed, 17 insertions(+)

diff --git a/folly/experimental/observer/Observer-inl.h b/folly/experimental/observer/Observer-inl.h
index eb1338d7..a73033c4 100644
--- a/folly/experimental/observer/Observer-inl.h
+++ b/folly/experimental/observer/Observer-inl.h
@@ -58,6 +58,10 @@ TLObserver<T>::TLObserver(Observer<T> observer)
     : observer_(observer),
       snapshot_([&] { return new Snapshot<T>(observer_.getSnapshot()); }) {}
 
+template <typename T>
+TLObserver<T>::TLObserver(const TLObserver<T>& other)
+    : TLObserver(other.observer_) {}
+
 template <typename T>
 const Snapshot<T>& TLObserver<T>::getSnapshotRef() const {
   auto& snapshot = *snapshot_;
diff --git a/folly/experimental/observer/Observer.h b/folly/experimental/observer/Observer.h
index 8037b24d..bad88e14 100644
--- a/folly/experimental/observer/Observer.h
+++ b/folly/experimental/observer/Observer.h
@@ -158,6 +158,7 @@ template <typename T>
 class TLObserver {
  public:
   explicit TLObserver(Observer<T> observer);
+  TLObserver(const TLObserver<T>& other);
 
   const Snapshot<T>& getSnapshotRef() const;
   const Snapshot<T>& operator*() const {
diff --git a/folly/experimental/observer/test/ObserverTest.cpp b/folly/experimental/observer/test/ObserverTest.cpp
index c2be17b9..f540ffa9 100644
--- a/folly/experimental/observer/test/ObserverTest.cpp
+++ b/folly/experimental/observer/test/ObserverTest.cpp
@@ -248,3 +248,15 @@ TEST(Observer, Stress) {
     }
   });
 }
+
+TEST(Observer, TLObserver) {
+  auto createTLObserver = [](int value) {
+    return folly::observer::makeTLObserver([=] { return value; });
+  };
+
+  auto k =
+      std::make_unique<folly::observer::TLObserver<int>>(createTLObserver(42));
+  EXPECT_EQ(42, ***k);
+  k = std::make_unique<folly::observer::TLObserver<int>>(createTLObserver(41));
+  EXPECT_EQ(41, ***k);
+}
-- 
2.34.1