Change the way we look up a result class in Operation modules

lib/mongo/operation/write/gle.rb

@@ -26,8 +26,8 @@ module GLE
 
         def execute_message(context)
           context.with_connection do |connection|
-            result_class = defined?(self.class::LegacyResult) ? self.class::LegacyResult :
-                defined?(self.class::Result) ? self.class::Result : Result
+            result_class = self.class.const_defined?(:LegacyResult, false) ? self.class::LegacyResult :
+                self.class.const_defined?(:Result, false) ? self.class::Result : Result
             result_class.new(connection.dispatch([ message, gle ].compact)).validate!
           end
         end

lib/mongo/operation/write/write_command_enabled.rb

@@ -44,7 +44,7 @@ def execute(context)
         private
 
         def execute_write_command(context)
-          result_class = defined?(self.class::Result) ? self.class::Result : Result
+          result_class = self.class.const_defined?(:Result, false) ? self.class::Result : Result
           result_class.new(write_command_op.execute(context)).validate!
         end
       end

spec/mongo/operation/result_spec.rb

@@ -272,4 +272,23 @@
       end
     end
   end
+
+  context 'when there is a top-level Result class defined' do
+
+    before do
+      class Result
+        def get_result
+          Mongo::Client.new([DEFAULT_ADDRESS], TEST_OPTIONS).database.command(:ping => 1)
+        end
+      end
+    end
+
+    let(:result) do
+      Result.new.get_result
+    end
+
+    it 'uses the Result class of the operation' do
+      expect(result).to be_a(Mongo::Operation::Result)
+    end
+  end
 end