Fixed std::initializer_list assignment issues for open-addressing containers (#277)

* fixed #276

* used range insert, stylistic this->

* assigned non-empty std::initializer_lists

test/unordered/assign_tests.cpp

@@ -7,12 +7,16 @@
 #include "../helpers/unordered.hpp"
 
 #include "../helpers/test.hpp"
+#include "../helpers/replace_allocator.hpp"
 #include "../objects/test.hpp"
 #include "../objects/cxx11_allocator.hpp"
+#include "../objects/non_default_ctble_allocator.hpp"
 #include "../helpers/random_values.hpp"
 #include "../helpers/tracker.hpp"
 #include "../helpers/equivalent.hpp"
 
+#include <vector>
+
 #if defined(BOOST_MSVC)
 #pragma warning(disable : 4127) // conditional expression is constant
 #endif
@@ -288,6 +292,27 @@ namespace assign_tests {
       }
 #endif
     }
+  
+    BOOST_LIGHTWEIGHT_TEST_OSTREAM << "gh276\n";
+    {
+      // https://github.com/boostorg/unordered/issues/276
+
+      using value_type = typename T::value_type;
+      using replaced_allocator_container = test::replace_allocator<
+        T, test::non_default_ctble_allocator<int> >;
+      using replaced_allocator_type = 
+        typename replaced_allocator_container::allocator_type;
+      
+      test::random_values<T> v(4, generator);
+      std::vector<value_type> vv(v.begin(), v.end());
+
+      replaced_allocator_container
+        x(replaced_allocator_type(0)),
+        y(vv.begin(), vv.begin() + 4, replaced_allocator_type(0));
+
+      x = {vv[0], vv[1], vv[2], vv[3]};
+      BOOST_TEST(x == y);
+    }
   }
 
   using test::default_generator;