redesigned init_type/value_type machinery

include/boost/unordered/detail/foa.hpp

@@ -829,6 +829,11 @@ table:empty_value<Hash,0>,empty_value<Pred,1>,empty_value<Allocator,1>
 public:
   using key_type=typename type_policy::key_type;
   using init_type=typename type_policy::init_type;
+
+private:
+  using moved_type=typename type_policy::moved_type;
+
+public:
   using value_type=typename type_policy::value_type;
 
 private:
@@ -995,7 +1000,7 @@ public:
            */
 
           x.for_all_elements([this](value_type* p){
-            unchecked_insert(std::move(*p));
+            unchecked_insert(type_policy::move(*p));
           });
         }
         BOOST_CATCH(...){
@@ -1221,6 +1226,17 @@ private:
     return type_policy::extract(x);
   }
 
+  template<
+    bool dependent_value=false,
+    typename std::enable_if<
+      has_different_init_type||dependent_value>::type* =nullptr
+  >
+  static inline auto key_from(const moved_type& x)
+    ->decltype(type_policy::extract(x))
+  {
+    return type_policy::extract(x);
+  }
+
   static inline auto key_from(const value_type& x)
     ->decltype(type_policy::extract(x))
   {
@@ -1361,9 +1377,8 @@ private:
   void nosize_transfer_element(value_type* p,const arrays_type& arrays_)
   {
     auto hash=h()(key_from(*p));
-    type_policy::move_parts_to(
-      *p,
-      bind_unchecked_emplace_at{this,arrays_,position_for(hash,arrays_),hash});
+    nosize_unchecked_emplace_at(
+      arrays_,position_for(hash,arrays_),hash,type_policy::move(*p));
     destroy_element(p);
   }
 
@@ -1429,21 +1444,6 @@ private:
   }
 #endif
 
-  struct bind_unchecked_emplace_at
-  {
-    template<typename... Args>
-    iterator operator()(Args&&... args)const
-    {
-      return this_->nosize_unchecked_emplace_at(
-        arrays,pos0,hash,std::forward<Args>(args)...);
-    }
-
-    table*             this_;
-    const arrays_type& arrays;
-    std::size_t        pos0;
-    std::size_t        hash;
-  };
-
   template<typename F>
   void for_all_elements(F f)const
   {

include/boost/unordered/unordered_flat_map.hpp

@@ -30,14 +30,16 @@ namespace boost {
       {
         using key_type = Key;
         using init_type = std::pair<Key, T>;
+        using moved_type = std::pair<Key&&, T&&>;
         using value_type = std::pair<Key const, T>;
         static Key const& extract(init_type const& kv) { return kv.first; }
         static Key const& extract(value_type const& kv) { return kv.first; }
+        static Key const& extract(moved_type const& kv) { return kv.first; }
 
-        template <typename F> static void move_parts_to(value_type& x, F f)
+        static moved_type move(value_type& x)
         {
           // TODO: we probably need to launder here
-          f(std::move(const_cast<Key&>(x.first)), std::move(x.second));
+          return {std::move(const_cast<Key&>(x.first)), std::move(x.second)};
         }
       };
 

include/boost/unordered/unordered_flat_set.hpp

@@ -30,13 +30,10 @@ namespace boost {
       {
         using key_type = Key;
         using init_type = Key;
+        using moved_type = Key;
         using value_type = Key;
         static Key const& extract(value_type const& key) { return key; }
-
-        template <typename F> static void move_parts_to(value_type& x, F f)
-        {
-          f(std::move(x));
-        }
+        static Key&& move(value_type& x) { return std::move(x); }
       };
 
       using table_type = detail::foa::table<set_types, Hash, KeyEqual,