[PATCH] Simplify _Node_insert_return to avoid including

[Jonathan Wakely]

We can use auto return types and if constexpr to do this without
including <tuple>.

        * include/bits/node_handle.h (_Node_insert_return::get): Avoid
        use of std::tie and std::get.

Tested powerpc64le-linux, committed to trunk.


commit 397d3b68eb53ff6b229ac777a05dff4ae842a19b
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Fri Oct 27 18:07:35 2017 +0100

    Simplify _Node_insert_return to avoid including <tuple>
    
            * include/bits/node_handle.h (_Node_insert_return::get): Avoid
            use of std::tie and std::get.

diff --git a/libstdc++-v3/include/bits/node_handle.h 
b/libstdc++-v3/include/bits/node_handle.h
index c7694a1e0ef..f93bfd7f686 100644
--- a/libstdc++-v3/include/bits/node_handle.h
+++ b/libstdc++-v3/include/bits/node_handle.h
@@ -37,7 +37,6 @@
 # define __cpp_lib_node_extract 201606
 
 #include <optional>
-#include <tuple>
 #include <bits/alloc_traits.h>
 #include <bits/ptr_traits.h>
 
@@ -286,22 +285,50 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       template<size_t _Idx>
        decltype(auto) get() &
-       { return std::get<_Idx>(std::tie(inserted, position, node)); }
+       {
+         static_assert(_Idx < 3);
+         if constexpr (_Idx == 0)
+           return inserted;
+         else if constexpr (_Idx == 1)
+           return position;
+         else if constexpr (_Idx == 2)
+           return node;
+       }
 
       template<size_t _Idx>
        decltype(auto) get() const &
-       { return std::get<_Idx>(std::tie(inserted, position, node)); }
+       {
+         static_assert(_Idx < 3);
+         if constexpr (_Idx == 0)
+           return inserted;
+         else if constexpr (_Idx == 1)
+           return position;
+         else if constexpr (_Idx == 2)
+           return node;
+       }
 
       template<size_t _Idx>
        decltype(auto) get() &&
        {
-         return std::move(std::get<_Idx>(std::tie(inserted, position, node)));
+         static_assert(_Idx < 3);
+         if constexpr (_Idx == 0)
+           return std::move(inserted);
+         else if constexpr (_Idx == 1)
+           return std::move(position);
+         else if constexpr (_Idx == 2)
+           return std::move(node);
        }
 
       template<size_t _Idx>
        decltype(auto) get() const &&
        {
-         return std::move(std::get<_Idx>(std::tie(inserted, position, node)));
+         static_assert(_Idx < 3);
+         if constexpr (_Idx == 0)
+           return std::move(inserted);
+         else if constexpr (_Idx == 1)
+           return std::move(position);
+         else if constexpr (_Idx == 2)
+           return std::move(node);
        }
     };