From a2284544a152bbe3c03408fa63acba7d9d55a9e5 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Mon, 17 Oct 2016 13:23:09 +0100
Subject: [PATCH] PR77998 Remove std::thread::_Invoker::result_type

	PR libstdc++/77998
	* include/std/future (__future_base::_Deferred_state)
	(__future_base::_Async_state_impl): Use decltype to deduce return
	type, instead of _Invoker::result_type.
	* include/std/thread (thread::_Invoker::operator()): Likewise.
	(thread::_Invoker::result_type): Remove.

From-SVN: r241236
---
 libstdc++-v3/ChangeLog          | 7 +++++++
 libstdc++-v3/include/std/future | 6 ++++--
 libstdc++-v3/include/std/thread | 9 +++------
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index ed572815d64..31280a36acf 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,12 @@
 2016-10-17  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/77998
+	* include/std/future (__future_base::_Deferred_state)
+	(__future_base::_Async_state_impl): Use decltype to deduce return
+	type, instead of _Invoker::result_type.
+	* include/std/thread (thread::_Invoker::operator()): Likewise.
+	(thread::_Invoker::result_type): Remove.
+
 	PR libstdc++/77987
 	* include/bits/unique_ptr.h (unique_ptr<T[], D>::reset<U>(U)): Copy
 	value to pointer of the correct type to swap, to support conversions
diff --git a/libstdc++-v3/include/std/future b/libstdc++-v3/include/std/future
index 31a21f976ee..5542d49584f 100644
--- a/libstdc++-v3/include/std/future
+++ b/libstdc++-v3/include/std/future
@@ -561,10 +561,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     class _Async_state_commonV2;
 #endif
 
-    template<typename _BoundFn, typename = typename _BoundFn::result_type>
+    template<typename _BoundFn,
+	     typename _Res = decltype(std::declval<_BoundFn&>()())>
       class _Deferred_state;
 
-    template<typename _BoundFn, typename = typename _BoundFn::result_type>
+    template<typename _BoundFn,
+	     typename _Res = decltype(std::declval<_BoundFn&>()())>
       class _Async_state_impl;
 
     template<typename _Signature>
diff --git a/libstdc++-v3/include/std/thread b/libstdc++-v3/include/std/thread
index 7a3c4078cc1..576e5776e6e 100644
--- a/libstdc++-v3/include/std/thread
+++ b/libstdc++-v3/include/std/thread
@@ -235,14 +235,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	using _Indices
 	  = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
 
-	using result_type
-	  = decltype(std::declval<_Invoker>()._M_invoke(_Indices()));
-
-	result_type
+	auto
 	operator()()
-	noexcept(noexcept(std::declval<_Invoker>()._M_invoke(_Indices())))
+	noexcept(noexcept(std::declval<_Invoker&>()._M_invoke(_Indices())))
+	-> decltype(std::declval<_Invoker&>()._M_invoke(_Indices()))
 	{ return _M_invoke(_Indices()); }
-
       };
 
     // Alias for _Invoker<tuple<DECAY_COPY(_Tp)...>>
-- 
2.30.2