Implement proxy erase(iterator)

include/boost/unordered/detail/foa/table.hpp

@@ -348,17 +348,40 @@ public:
   >::type
   insert(element_type&& x){return emplace_impl(std::move(x));}
 
+  struct proxy_erase {
+    const_iterator pos;
+    operator iterator()const noexcept
+    {
+      auto it=pos;
+      it.increment();
+      return iterator(const_iterator_cast_tag{},it);
+    }
+
     template<
       bool dependent_value=false,
       typename std::enable_if<
         has_mutable_iterator||dependent_value>::type* =nullptr
     >
-  void erase(iterator pos)noexcept{return erase(const_iterator(pos));}
+    operator const_iterator()const noexcept
+    {
+      auto it=pos;
+      it.increment();
+      return it;
+    }
+  };
+
+  template<
+    bool dependent_value=false,
+    typename std::enable_if<
+      has_mutable_iterator||dependent_value>::type* =nullptr
+  >
+  proxy_erase erase(iterator pos)noexcept{return erase(const_iterator(pos));}
 
   BOOST_FORCEINLINE
-  void erase(const_iterator pos)noexcept
+  proxy_erase erase(const_iterator pos)noexcept
   {
     super::erase(pos.pc,pos.p);
+    return proxy_erase{pos};
   }
 
   template<typename Key>

include/boost/unordered/unordered_flat_map.hpp

@@ -381,11 +381,17 @@ namespace boost {
           .first;
       }
 
-      BOOST_FORCEINLINE void erase(iterator pos) { table_.erase(pos); }
+      BOOST_FORCEINLINE typename table_type::proxy_erase erase(iterator pos)
-      BOOST_FORCEINLINE void erase(const_iterator pos)
       {
         return table_.erase(pos);
       }
+
+      BOOST_FORCEINLINE typename table_type::proxy_erase erase(
+        const_iterator pos)
+      {
+        return table_.erase(pos);
+      }
+
       iterator erase(const_iterator first, const_iterator last)
       {
         while (first != last) {

include/boost/unordered/unordered_flat_set.hpp

@@ -282,10 +282,12 @@ namespace boost {
         return table_.emplace(std::forward<Args>(args)...).first;
       }
 
-      BOOST_FORCEINLINE void erase(const_iterator pos)
+      BOOST_FORCEINLINE typename table_type::proxy_erase erase(
+        const_iterator pos)
       {
         return table_.erase(pos);
       }
+
       iterator erase(const_iterator first, const_iterator last)
       {
         while (first != last) {

include/boost/unordered/unordered_node_map.hpp

@@ -458,11 +458,17 @@ namespace boost {
           .first;
       }
 
-      BOOST_FORCEINLINE void erase(iterator pos) { table_.erase(pos); }
+      BOOST_FORCEINLINE typename table_type::proxy_erase erase(iterator pos)
-      BOOST_FORCEINLINE void erase(const_iterator pos)
       {
         return table_.erase(pos);
       }
+
+      BOOST_FORCEINLINE typename table_type::proxy_erase erase(
+        const_iterator pos)
+      {
+        return table_.erase(pos);
+      }
+
       iterator erase(const_iterator first, const_iterator last)
       {
         while (first != last) {

include/boost/unordered/unordered_node_set.hpp

@@ -352,10 +352,12 @@ namespace boost {
         return table_.emplace(std::forward<Args>(args)...).first;
       }
 
-      BOOST_FORCEINLINE void erase(const_iterator pos)
+      BOOST_FORCEINLINE typename table_type::proxy_erase erase(
+        const_iterator pos)
       {
         return table_.erase(pos);
       }
+
       iterator erase(const_iterator first, const_iterator last)
       {
         while (first != last) {

test/unordered/compile_tests.hpp

@@ -844,7 +844,7 @@ void unordered_copyable_test(X& x, Key& k, T& t, Hash& hf, Pred& eq)
   a10.insert(t);
   q = a10.cbegin();
 #ifdef BOOST_UNORDERED_FOA_TESTS
-  BOOST_STATIC_ASSERT(std::is_same<void, decltype(a10.erase(q))>::value);
+  test::check_return_type<iterator>::convertible(a10.erase(q));
 #else
   test::check_return_type<iterator>::equals(a10.erase(q));
 #endif
@@ -937,7 +937,7 @@ void unordered_movable_test(X& x, Key& k, T& /* t */, Hash& hf, Pred& eq)
   a10.insert(boost::move(v5));
   q = a10.cbegin();
 #ifdef BOOST_UNORDERED_FOA_TESTS
-  BOOST_STATIC_ASSERT(std::is_same<void, decltype(a10.erase(q))>::value);
+  test::check_return_type<iterator>::convertible(a10.erase(q));
 #else
   test::check_return_type<iterator>::equals(a10.erase(q));
 #endif

test/unordered/erase_tests.cpp

@@ -23,9 +23,7 @@ namespace erase_tests {
   template <class Container>
   void erase_tests1(Container*, test::random_generator generator)
   {
-#ifndef BOOST_UNORDERED_FOA_TESTS
     typedef typename Container::iterator iterator;
-#endif
     typedef typename Container::const_iterator c_iterator;
 
     BOOST_LIGHTWEIGHT_TEST_OSTREAM << "Erase by key.\n";
@@ -59,12 +57,8 @@ namespace erase_tests {
       while (size > 0 && !x.empty()) {
         typename Container::key_type key = test::get_key<Container>(*x.begin());
         std::size_t count = x.count(key);
-#ifdef BOOST_UNORDERED_FOA_TESTS
-        x.erase(x.begin());
-#else
         iterator pos = x.erase(x.begin());
-        BOOST_TEST(pos == x.begin());
+        BOOST_ASSERT(BOOST_TEST(pos == x.begin()));
-#endif
         --size;
         BOOST_TEST(x.count(key) == count - 1);
         BOOST_TEST(x.size() == size);
@@ -95,15 +89,10 @@ namespace erase_tests {
         typename Container::key_type key = test::get_key<Container>(*pos);
         std::size_t count = x.count(key);
         BOOST_TEST(count > 0);
-#ifdef BOOST_UNORDERED_FOA_TESTS
-        x.erase(pos);
-        --size;
-#else
         BOOST_TEST(next == x.erase(pos));
         --size;
         if (size > 0)
           BOOST_TEST(index == 0 ? next == x.begin() : next == test::next(prev));
-#endif
         BOOST_TEST(x.count(key) == count - 1);
         if (x.count(key) != count - 1) {
           BOOST_LIGHTWEIGHT_TEST_OSTREAM << count << " => " << x.count(key)

test/unordered/transparent_tests.cpp

@@ -1065,11 +1065,7 @@ typedef boost::unordered_map<int, int, transparent_hasher,
 // test that in the presence of the member function template `erase()`, we still
 // invoke the correct iterator overloads when the type is implicitly convertible
 //
-#ifdef BOOST_UNORDERED_FOA_TESTS
-void
-#else
 transparent_unordered_map::iterator
-#endif
 map_erase_overload_compile_test()
 {
   convertible_to_iterator<transparent_unordered_map> c;
@@ -1079,11 +1075,7 @@ map_erase_overload_compile_test()
   return map.erase(c);
 }
 
-#ifdef BOOST_UNORDERED_FOA_TESTS
-void
-#else
 transparent_unordered_map::const_iterator
-#endif
 map_erase_const_overload_compile_test()
 {
   convertible_to_const_iterator<transparent_unordered_map> c;
@@ -1226,11 +1218,7 @@ typedef boost::unordered_multiset<int, transparent_hasher,
   transparent_unordered_multiset;
 #endif
 
-#ifdef BOOST_UNORDERED_FOA_TESTS
-void
-#else
 transparent_unordered_set::iterator
-#endif
 set_erase_overload_compile_test()
 {
   convertible_to_iterator<transparent_unordered_set> c;
@@ -1240,11 +1228,7 @@ set_erase_overload_compile_test()
   return set.erase(c);
 }
 
-#ifdef BOOST_UNORDERED_FOA_TESTS
-void
-#else
 transparent_unordered_set::const_iterator
-#endif
 set_erase_const_overload_compile_test()
 {
   convertible_to_const_iterator<transparent_unordered_set> c;