From afd43cf672d42bac45eee7840da020bb74008afe Mon Sep 17 00:00:00 2001
From: Jeroen Vermeulen <jtvjtv@gmail.com>
Date: Wed, 19 Feb 2020 14:02:47 +0100
Subject: [PATCH] Use `invoke_result_t`.

---
 include/pqxx/transactor.hxx | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/pqxx/transactor.hxx b/include/pqxx/transactor.hxx
index 928fe67c9..af4bc19a1 100644
--- a/include/pqxx/transactor.hxx
+++ b/include/pqxx/transactor.hxx
@@ -15,6 +15,7 @@
 #include "pqxx/internal/compiler-internal-pre.hxx"
 
 #include <functional>
+#include <type_traits>
 
 #include "pqxx/connection.hxx"
 #include "pqxx/transaction.hxx"
@@ -97,7 +98,7 @@ namespace pqxx
  */
 template<typename TRANSACTION_CALLBACK>
 inline auto perform(TRANSACTION_CALLBACK &&callback, int attempts = 3)
-  -> decltype(std::invoke(callback))
+  -> std::invoke_result_t<TRANSACTION_CALLBACK>
 {
   if (attempts <= 0)
     throw std::invalid_argument{