From a107a89991d55d177a691243a420f846bc36f685 Mon Sep 17 00:00:00 2001
From: Denis Blank <denis.blank@outlook.com>
Date: Tue, 6 Feb 2018 00:18:06 +0100
Subject: [PATCH] Convert all invoke_result traits into decltype(...)

---
 include/continuable/detail/traverse.hpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/continuable/detail/traverse.hpp b/include/continuable/detail/traverse.hpp
index fdc1522..e1d9309 100644
--- a/include/continuable/detail/traverse.hpp
+++ b/include/continuable/detail/traverse.hpp
@@ -412,13 +412,13 @@ using dereferenced_of_t =
 /// references we try to construct the container from a copied
 /// version.
 template <typename Container, typename Mapping>
-using mapped_type_from_t = dereferenced_of_t<spreading::unpacked_of_t<
-    typename invoke_result<Mapping, element_of_t<Container>>::type>>;
+using mapped_type_from_t = dereferenced_of_t<spreading::unpacked_of_t<decltype(
+    std::declval<Mapping>()(std::declval<element_of_t<Container>>()))>>;
 
 /// Deduces to a true_type if the mapping maps to zero elements.
 template <typename T, typename M>
-using is_empty_mapped = spreading::is_empty_spread<typename std::decay<
-    typename invoke_result<M, element_of_t<T>>::type>::type>;
+using is_empty_mapped = spreading::is_empty_spread<typename std::decay<decltype(
+    std::declval<M>()(std::declval<element_of_t<T>>()))>::type>;
 
 /// We are allowed to reuse the container if we map to the same
 /// type we are accepting and when we have
@@ -588,8 +588,8 @@ struct tuple_like_remapper<
   M mapper_;
 
   template <typename... Args>
-  auto operator()(Args&&... args) ->
-      typename invoke_result<typename invoke_result<M, OldArg>::type>::type {
+  auto operator()(Args&&... args)
+      -> decltype((std::declval<M>()(std::declval<OldArg>()))()) {
     int dummy[] = {0, ((void)mapper_(std::forward<Args>(args)), 0)...};
     (void)dummy;
   }