From 3a7cbbe49433606c07f53a32cca05d7cb221e433 Mon Sep 17 00:00:00 2001
From: Christopher Dykes <cdykes@fb.com>
Date: Wed, 12 Apr 2017 18:19:37 -0700
Subject: [PATCH] Fix the last issues with exception_wrapper under MSVC

Summary:
Well, MSVC 2017 anyways.
MSVC 2017 wasn't able to handle the decltype in the type specialization, which was also entirely unnecesary.

Reviewed By: yfeldblum

Differential Revision: D4880272

fbshipit-source-id: b6deed72a12d4b58d6eca200e7287e536f94ca30
---
 folly/ExceptionWrapper-inl.h | 32 ++++++++++++++++++--------------
 folly/ExceptionWrapper.h     |  2 --
 2 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/folly/ExceptionWrapper-inl.h b/folly/ExceptionWrapper-inl.h
index 17548445..0de18b0c 100644
--- a/folly/ExceptionWrapper-inl.h
+++ b/folly/ExceptionWrapper-inl.h
@@ -21,32 +21,36 @@
 namespace folly {
 
 template <class Fn>
-struct exception_wrapper::arg_type2_ {};
+struct exception_wrapper::arg_type_
+    : public arg_type_<decltype(&Fn::operator())> {
+};
 template <class Ret, class Class, class Arg>
-struct exception_wrapper::arg_type2_<Ret (Class::*)(Arg)> {
+struct exception_wrapper::arg_type_<Ret (Class::*)(Arg)> {
   using type = Arg;
 };
 template <class Ret, class Class, class Arg>
-struct exception_wrapper::arg_type2_<Ret (Class::*)(Arg) const> {
+struct exception_wrapper::arg_type_<Ret (Class::*)(Arg) const> {
+  using type = Arg;
+};
+template <class Ret, class Arg>
+struct exception_wrapper::arg_type_<Ret (Arg)> {
+  using type = Arg;
+};
+template <class Ret, class Arg>
+struct exception_wrapper::arg_type_<Ret (*)(Arg)> {
   using type = Arg;
 };
 template <class Ret, class Class>
-struct exception_wrapper::arg_type2_<Ret (Class::*)(...)> {
+struct exception_wrapper::arg_type_<Ret (Class::*)(...)> {
   using type = AnyException;
 };
 template <class Ret, class Class>
-struct exception_wrapper::arg_type2_<Ret (Class::*)(...) const> {
+struct exception_wrapper::arg_type_<Ret (Class::*)(...) const> {
   using type = AnyException;
 };
-
-template <class Fn, class>
-struct exception_wrapper::arg_type_ {};
-template <class Fn>
-struct exception_wrapper::arg_type_<Fn, void_t<decltype(&Fn::operator())>>
-    : public arg_type2_<decltype(&Fn::operator())> {};
-template <class Ret, class Arg>
-struct exception_wrapper::arg_type_<Ret (*)(Arg)> {
-  using type = Arg;
+template <class Ret>
+struct exception_wrapper::arg_type_<Ret (...)> {
+  using type = AnyException;
 };
 template <class Ret>
 struct exception_wrapper::arg_type_<Ret (*)(...)> {
diff --git a/folly/ExceptionWrapper.h b/folly/ExceptionWrapper.h
index fa91d458..dcdf8628 100644
--- a/folly/ExceptionWrapper.h
+++ b/folly/ExceptionWrapper.h
@@ -168,8 +168,6 @@ class exception_wrapper final {
   };
 
   template <class Fn>
-  struct arg_type2_;
-  template <class Fn, class = void>
   struct arg_type_;
   template <class Fn>
   using arg_type = _t<arg_type_<Fn>>;
-- 
2.34.1