fix HashWithIndifferentAccess.[] method

activesupport/lib/active_support/hash_with_indifferent_access.rb

@@ -42,6 +42,10 @@ def self.new_from_hash_copying_default(hash)
       end
     end
 
+    def self.[](*args)
+      new.merge(Hash[*args])
+    end
+
     alias_method :regular_writer, :[]= unless method_defined?(:regular_writer)
     alias_method :regular_update, :update unless method_defined?(:regular_update)
 

activesupport/test/core_ext/hash_ext_test.rb

@@ -388,6 +388,15 @@ def test_store_on_indifferent_access
     assert_equal expected, hash
   end
 
+  def test_constructor_on_indifferent_access
+    hash = HashWithIndifferentAccess[:foo, 1]
+    assert_equal 1, hash[:foo]
+    assert_equal 1, hash['foo']
+    hash[:foo] = 3
+    assert_equal 3, hash[:foo]
+    assert_equal 3, hash['foo']
+  end
+
   def test_reverse_merge
     defaults = { :a => "x", :b => "y", :c => 10 }.freeze
     options  = { :a => 1, :b => 2 }