Hash sub class creates new sub class objects instead of Hash

mrbgems/mruby-hash-ext/mrblib/hash.rb

@@ -28,11 +28,11 @@ class Hash
     if length == 1
       o = object[0]
       if o.respond_to?(:to_hash)
-        h = Hash.new
+        h = self.new
         object[0].to_hash.each { |k, v| h[k] = v }
         return h
       elsif o.respond_to?(:to_a)
-        h = Hash.new
+        h = self.new
         o.to_a.each do |i|
           raise ArgumentError, "wrong element type #{i.class} (expected array)" unless i.respond_to?(:to_a)
           k, v = nil
@@ -53,7 +53,7 @@ class Hash
     unless length % 2 == 0
       raise ArgumentError, 'odd number of arguments for Hash'
     end
-    h = Hash.new
+    h = self.new
     0.step(length - 2, 2) do |i|
       h[object[i]] = object[i + 1]
     end
@@ -211,7 +211,7 @@ class Hash
   #
 
   def invert
-    h = Hash.new
+    h = self.class.new
     self.each {|k, v| h[v] = k }
     h
   end

mrbgems/mruby-hash-ext/test/hash.rb

@@ -39,6 +39,12 @@ assert('Hash.[] "c_key", "c_value"') do
   end
 end
 
+assert('Hash.[] for sub class') do
+  sub_hash_class = Class.new(Hash)
+  sub_hash = sub_hash_class[]
+  assert_equal(sub_hash_class, sub_hash.class)
+end
+
 assert('Hash.try_convert') do
   assert_nil Hash.try_convert(nil)
   assert_nil Hash.try_convert("{1=>2}")
@@ -143,6 +149,12 @@ assert("Hash#invert") do
   assert_equal('b', h[2])
 end
 
+assert("Hash#invert with sub class") do
+  sub_hash_class = Class.new(Hash)
+  sub_hash = sub_hash_class.new
+  assert_equal(sub_hash_class, sub_hash.invert.class)
+end
+
 assert("Hash#keep_if") do
   h = { 1 => 2, 3 => 4, 5 => 6 }
   assert_equal({3=>4,5=>6}, h.keep_if {|k, v| k + v >= 7 })