Fix "count" with heterogeneous lookups in flat_map and flat_set

include/boost/container/flat_set.hpp

@@ -925,7 +925,9 @@ class flat_set
    //! <b>Complexity</b>: log(size())+count(k)
    template<typename K>
    BOOST_CONTAINER_FORCEINLINE size_type count(const K& x) const
-   {  return static_cast<size_type>(this->tree_t::find(x) != this->tree_t::cend());  }
+      //Don't use find() != end optimization here as transparent comparators with key K might
+      //return a different range than key_type (which can only return a single element range)
+   {  return this->tree_t::count(x);  }
 
    #if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
 
@@ -1031,6 +1033,8 @@ class flat_set
    //! <b>Complexity</b>: Logarithmic
    template<typename K>
    std::pair<iterator,iterator> equal_range(const K& x)
+      //Don't use lower_bound_range optimization here as transparent comparators with key K might
+      //return a different range than key_type (which can only return a single element range)
    {  return this->tree_t::equal_range(x);  }
 
    //! <b>Requires</b>: This overload is available only if
@@ -1041,6 +1045,8 @@ class flat_set
    //! <b>Complexity</b>: Logarithmic
    template<typename K>
    std::pair<const_iterator,const_iterator> equal_range(const K& x) const
+      //Don't use lower_bound_range optimization here as transparent comparators with key K might
+      //return a different range than key_type (which can only return a single element range)
    {  return this->tree_t::equal_range(x);  }
 
    #if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)