From 24b4725966b4c22c0144c519317ba05b8479df6c Mon Sep 17 00:00:00 2001
From: Simon Brand <tartanllama@gmail.com>
Date: Tue, 19 Dec 2017 15:04:45 +0000
Subject: [PATCH 1/5] Fix #1

---
 CMakeLists.txt   |  1 +
 tests/issues.cpp | 26 ++++++++++++++++++++++++++
 tl/expected.hpp  | 22 +++++++++++++---------
 3 files changed, 40 insertions(+), 9 deletions(-)
 create mode 100644 tests/issues.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3e7bcd7..fe45fae 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,6 +12,7 @@ set(TEST_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/tests/main.cpp
                  ${CMAKE_CURRENT_SOURCE_DIR}/tests/extensions.cpp
                  ${CMAKE_CURRENT_SOURCE_DIR}/tests/assignment.cpp
                  ${CMAKE_CURRENT_SOURCE_DIR}/tests/emplace.cpp
+                 ${CMAKE_CURRENT_SOURCE_DIR}/tests/issues.cpp
                  ${CMAKE_CURRENT_SOURCE_DIR}/tests/bases.cpp
                  ${CMAKE_CURRENT_SOURCE_DIR}/tests/observers.cpp
                  ${CMAKE_CURRENT_SOURCE_DIR}/tests/constructors.cpp)
diff --git a/tests/issues.cpp b/tests/issues.cpp
new file mode 100644
index 0000000..2dc4201
--- /dev/null
+++ b/tests/issues.cpp
@@ -0,0 +1,26 @@
+#include "catch.hpp"
+#include "expected.hpp"
+
+#include <string>
+
+using std::string;
+
+tl::expected<int, string> getInt3(int val)
+{
+    return val;
+}
+
+tl::expected<int, string> getInt2(int val)
+{
+    return val;
+}
+
+tl::expected<int, string> getInt1()
+{
+    return getInt2(5).and_then(getInt3);
+}
+
+
+TEST_CASE("Issue 1", "[issues.1]") {
+    getInt1();
+}
diff --git a/tl/expected.hpp b/tl/expected.hpp
index 4a61b65..6515668 100644
--- a/tl/expected.hpp
+++ b/tl/expected.hpp
@@ -999,8 +999,9 @@ public:
   /// is returned.
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &;
   template <class F>
-  TL_EXPECTED_11_CONSTEXPR detail::invoke_result_t<F, T &> and_then(F &&f) & {
-    using result = detail::invoke_result_t<F, T &>;
+  TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) &
+      -> decltype(detail::invoke(std::forward<F>(f), std::declval<T&>())) {
+    using result = decltype(detail::invoke(std::forward<F>(f), **this));
     static_assert(detail::is_expected<result>::value,
                   "F must return an expected");
 
@@ -1011,20 +1012,22 @@ public:
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &&;
   template <class F>
-  TL_EXPECTED_11_CONSTEXPR detail::invoke_result_t<F, T &&> and_then(F &&f) && {
-    using result = detail::invoke_result_t<F, T &&>;
+  TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) &&
+        -> decltype(detail::invoke(std::forward<F>(f), std::declval<T&&>())) {
+    using result = decltype(detail::invoke(std::forward<F>(f), std::move(**this)));
     static_assert(detail::is_expected<result>::value,
                   "F must return an expected");
 
-    return has_value() ? detail::invoke(std::forward<F>(f), **this)
+    return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
                        : result(unexpect, std::move(this->error()));
   }
 
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &;
   template <class F>
-  constexpr detail::invoke_result_t<F, const T &> and_then(F &&f) const & {
-    using result = detail::invoke_result_t<F, const T &>;
+  constexpr auto and_then(F &&f) const &
+      -> decltype(detail::invoke(std::forward<F>(f), std::declval<const T&>())) {
+      using result = decltype(detail::invoke(std::forward<F>(f), **this));
     static_assert(detail::is_expected<result>::value,
                   "F must return an expected");
 
@@ -1036,8 +1039,9 @@ public:
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &&;
   template <class F>
-  constexpr detail::invoke_result_t<F, const T &&> and_then(F &&f) const && {
-    using result = detail::invoke_result_t<F, const T &&>;
+  constexpr auto and_then(F &&f) const &&
+      -> decltype(detail::invoke(std::forward<F>(f), std::declval<const T&&>())) {
+    using result = decltype(detail::invoke(std::forward<F>(f), std::move(**this)));
     static_assert(detail::is_expected<result>::value,
                   "F must return an expected");
 

From d7c8a569ac572775e362ca8e6ba99586f8e16ea0 Mon Sep 17 00:00:00 2001
From: Simon Brand <tartanllama@gmail.com>
Date: Tue, 19 Dec 2017 15:23:56 +0000
Subject: [PATCH 2/5] Constexpr fixes

---
 tl/expected.hpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tl/expected.hpp b/tl/expected.hpp
index 6515668..c88f7fa 100644
--- a/tl/expected.hpp
+++ b/tl/expected.hpp
@@ -78,6 +78,12 @@
 #define TL_EXPECTED_GCC49_CONSTEXPR constexpr
 #endif
 
+#ifdef TL_EXPECTED_MSVC2015_CONSTEXPR
+#define TL_EXPECTED_MSVC2015_CONSTEXPR
+#else
+#define TL_EXPECTED_MSVC2015_CONSTEXPR constexpr
+#endif
+
 #if (__cplusplus == 201103L || defined(TL_EXPECTED_MSVC2015) ||                \
      defined(TL_EXPECTED_GCC49)) &&                                            \
     !defined(TL_EXPECTED_GCC54)
@@ -1380,7 +1386,7 @@ public:
       class U = T,
       detail::enable_if_t<!std::is_convertible<U &&, T>::value> * = nullptr,
       detail::expected_enable_forward_value<T, E, U> * = nullptr>
-  explicit constexpr expected(U &&v) : expected(in_place, std::forward<U>(v)) {}
+  explicit TL_EXPECTED_MSVC2015_CONSTEXPR expected(U &&v) : expected(in_place, std::forward<U>(v)) {}
 
   /// \exclude
   template <

From 00dea6263b2f3228ae6a2aaaa4750d194b0e581a Mon Sep 17 00:00:00 2001
From: Simon Brand <tartanllama@gmail.com>
Date: Tue, 19 Dec 2017 15:28:16 +0000
Subject: [PATCH 3/5] More constexpr fixes

---
 tl/expected.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tl/expected.hpp b/tl/expected.hpp
index c88f7fa..5634856 100644
--- a/tl/expected.hpp
+++ b/tl/expected.hpp
@@ -1393,7 +1393,7 @@ public:
       class U = T,
       detail::enable_if_t<std::is_convertible<U &&, T>::value> * = nullptr,
       detail::expected_enable_forward_value<T, E, U> * = nullptr>
-  constexpr expected(U &&v) : expected(in_place, std::forward<U>(v)) {}
+  TL_EXPECTED_MSVC2015_CONSTEXPR expected(U &&v) : expected(in_place, std::forward<U>(v)) {}
 
   template <
       class U = T,

From 950f0bf12f5aec3d61c3fbcaade79f94da75e1d0 Mon Sep 17 00:00:00 2001
From: Simon Brand <tartanllama@gmail.com>
Date: Tue, 19 Dec 2017 17:25:59 +0000
Subject: [PATCH 4/5] More constexpr fixes

---
 tl/expected.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tl/expected.hpp b/tl/expected.hpp
index 5634856..7af0855 100644
--- a/tl/expected.hpp
+++ b/tl/expected.hpp
@@ -78,7 +78,7 @@
 #define TL_EXPECTED_GCC49_CONSTEXPR constexpr
 #endif
 
-#ifdef TL_EXPECTED_MSVC2015_CONSTEXPR
+#ifdef TL_EXPECTED_MSVC2015
 #define TL_EXPECTED_MSVC2015_CONSTEXPR
 #else
 #define TL_EXPECTED_MSVC2015_CONSTEXPR constexpr

From 07f7b573904c29789bfb5a0f3258cfa03edcf6e3 Mon Sep 17 00:00:00 2001
From: Simon Brand <tartanllama@gmail.com>
Date: Tue, 19 Dec 2017 19:03:32 +0000
Subject: [PATCH 5/5] More constexpr fixes

---
 tl/expected.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tl/expected.hpp b/tl/expected.hpp
index 7af0855..604a869 100644
--- a/tl/expected.hpp
+++ b/tl/expected.hpp
@@ -368,7 +368,7 @@ template <class T, class E> struct expected_storage_base<T, E, true, true> {
 // T is trivial, E is not.
 template <class T, class E> struct expected_storage_base<T, E, true, false> {
   constexpr expected_storage_base() : m_val(T{}), m_has_val(true) {}
-  constexpr expected_storage_base(no_init_t) : m_has_val(false) {}
+  TL_EXPECTED_MSVC2015_CONSTEXPR expected_storage_base(no_init_t) : m_has_val(false) {}
 
   template <class... Args,
             detail::enable_if_t<std::is_constructible<T, Args &&...>::value> * =