From aa50c6b65ad077e8c0027c5627dc312525a5defc Mon Sep 17 00:00:00 2001
From: Jeremy Nimmer <jeremy.nimmer@tri.global>
Date: Wed, 28 Nov 2018 19:31:49 -0500
Subject: [PATCH] Fix duplicate definition of stx::in_place and related

In some cases, optional.hpp and variant.hpp still could not be included
in the same translation unit:

(1) If the user included variant.hpp first and optional.hpp second and
if <variant> was available, we'd see duplicate inplace_t and inplace.

(2) If the user included optional.hpp first and variant.hpp second and
if <optional> was available, we'd see duplicate inplace_t and inplace.

(3) If the user included optional.hpp first and variant.hpp second and
if <optional> was not available, we'd see duplicate in_place_type_t,
in_place_type, in_place_index_t, and in_place_index.

This improves on 6da04dc9898a2bc1724575b339d983b053d20d4f.
---
 include/stx/optional.hpp | 24 ++++++------------------
 include/stx/variant.hpp  |  2 +-
 2 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/include/stx/optional.hpp b/include/stx/optional.hpp
index 3f8c556..132e33a 100644
--- a/include/stx/optional.hpp
+++ b/include/stx/optional.hpp
@@ -37,8 +37,11 @@
             using std::nullopt_t;
             using std::nullopt;
             using std::make_optional;
+#       ifndef STX_HAVE_IN_PLACE_T
             using std::in_place_t;
             using std::in_place;
+#       define STX_HAVE_IN_PLACE_T 1
+#       endif // STX_HAVE_IN_PLACE_T
         }
 #       define STX_HAVE_STD_OPTIONAL 1
 #   elif __has_include(<experimental/optional>)
@@ -49,8 +52,11 @@
             using std::experimental::nullopt_t;
             using std::experimental::nullopt;
             using std::experimental::make_optional;
+#       ifndef STX_HAVE_IN_PLACE_T
             using std::experimental::in_place_t;
             using std::experimental::in_place;
+#       define STX_HAVE_IN_PLACE_T 1
+#       endif // STX_HAVE_IN_PLACE_T
         }
 #       define STX_HAVE_STD_OPTIONAL 1
 #    endif // __hasinclude(optional)
@@ -299,24 +305,6 @@ struct in_place_t {
 
 constexpr in_place_t in_place{};
 
-template <class T> struct in_place_type_t {
-    explicit in_place_type_t() = default;
-};
-
-
-template <size_t I> struct in_place_index_t {
-    explicit in_place_index_t() = default;
-};
-
-
-#if __cpp_variable_templates >= 201304
-template <class T>
-constexpr in_place_type_t<T> in_place_type{};
-template <size_t I>
-constexpr in_place_index_t<I> in_place_index{};
-#endif // __cpp_variable_templates
-
-
 #define STX_HAVE_IN_PLACE_T
 #endif // STX_HAVE_IN_PLACE_T
 
diff --git a/include/stx/variant.hpp b/include/stx/variant.hpp
index dbf79e6..4d6d41c 100644
--- a/include/stx/variant.hpp
+++ b/include/stx/variant.hpp
@@ -57,7 +57,7 @@
 #           ifndef STX_HAVE_IN_PLACE_T
             using std::in_place_t;
             using std::in_place;
-#           define STX_IN_PLACE_T 1
+#           define STX_HAVE_IN_PLACE_T 1
 #           endif
             using std::in_place_type_t;
             using std::in_place_type;