fix get_allocator private alloc_

Author: alfC

include/boost/multi/array.hpp

@@ -159,7 +159,8 @@ struct
 	using decay_type     = array<T, D, allocator_type>;
 
 	/// returns the allocator that is used to acquire/release memory and to construct/destroy the elements in that memory
-	BOOST_MULTI_HD constexpr auto get_allocator() const -> allocator_type { return this->alloc_; }
+	BOOST_MULTI_HD constexpr auto get_allocator() const -> allocator_type { return detail::array_allocator<
+	  typename allocator_traits<DummyAlloc>::template rebind_alloc<T>>::get_allocator(); }
 
 	/*[[deprecated]]*/ auto operator new(std::size_t count) -> void* { return ::operator new(count); }                  // overrides the deleted new operator in reference (base) class subarray
 	/*[[deprecated]]*/ auto operator new(std::size_t count, void* ptr) -> void* { return ::operator new(count, ptr); }  // overrides the deleted new operator in reference (base) class subarray

test/allocator.cpp

@@ -282,6 +282,8 @@ auto main() -> int {  // NOLINT(readability-function-cognitive-complexity,bugpro
 
 		multi::array<char, 2, std::pmr::polymorphic_allocator<char>> Barr({3, 2}, 'o', &pool);
 
+		BOOST_TEST( Aarr.get_allocator() == Barr.get_allocator() );
+
 		BOOST_TEST(( buffer != std::array<char, 13>{{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C'}} ));
 
 #ifdef __GLIBCXX__