From 46bb1ed780a2ce03d856a98d4e2061d7f13b6f8c Mon Sep 17 00:00:00 2001
From: Alexander Shaposhnikov <alexshap@fb.com>
Date: Tue, 28 Jul 2015 16:35:54 -0700
Subject: [PATCH] [folly] Enable support of applyTuple for const tuples

Summary: This diff fixes the helper template ReturnValue to enable using of applyTuple with
constant refs.

Reviewed By: @ot, @ddrcoder

Differential Revision: D2284733
---
 folly/ApplyTuple.h            | 6 +++---
 folly/test/ApplyTupleTest.cpp | 4 +++-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/folly/ApplyTuple.h b/folly/ApplyTuple.h
index 741429a4..a592704f 100644
--- a/folly/ApplyTuple.h
+++ b/folly/ApplyTuple.h
@@ -91,7 +91,7 @@ struct CallTuple {
 
 // The point of this meta function is to extract the contents of the
 // tuple as a parameter pack so we can pass it into std::result_of<>.
-template<class F, class Args> struct ReturnValue {};
+template<class F, class Args> struct ReturnValue;
 template<class F, class ...Args>
 struct ReturnValue<F,std::tuple<Args...>> {
   typedef typename std::result_of<F (Args...)>::type type;
@@ -104,12 +104,12 @@ struct ReturnValue<F,std::tuple<Args...>> {
 template<class Callable, class Tuple>
 typename detail::ReturnValue<
   typename std::decay<Callable>::type,
-  typename std::remove_reference<Tuple>::type
+  typename std::decay<Tuple>::type
 >::type
 applyTuple(const Callable& c, Tuple&& t) {
   typedef typename detail::ReturnValue<
     typename std::decay<Callable>::type,
-    typename std::remove_reference<Tuple>::type
+    typename std::decay<Tuple>::type
   >::type RetT;
   return detail::CallTuple<RetT>::call(c, std::forward<Tuple>(t));
 }
diff --git a/folly/test/ApplyTupleTest.cpp b/folly/test/ApplyTupleTest.cpp
index 195bb7b7..971f5b6d 100644
--- a/folly/test/ApplyTupleTest.cpp
+++ b/folly/test/ApplyTupleTest.cpp
@@ -86,7 +86,7 @@ struct GuardObj : GuardObjBase {
     : f_(std::move(f))
     , args_(std::move(args))
   {}
-  GuardObj(GuardObj&& g)
+  GuardObj(GuardObj&& g) noexcept
     : GuardObjBase(std::move(g))
     , f_(std::move(g.f_))
     , args_(std::move(g.args_))
@@ -163,4 +163,6 @@ TEST(ApplyTuple, Test) {
   Mover m;
   folly::applyTuple(move_only_func,
                     std::forward_as_tuple(std::forward<Mover>(Mover())));
+  const auto tuple3 = std::make_tuple(1, 2, 3.0);
+  folly::applyTuple(func, tuple3);
 }
-- 
2.34.1