Get rid of Base#merge_includes

activerecord/lib/active_record/base.rb

@@ -1583,11 +1583,6 @@ def construct_join(joins)
           end
         end
 
-        # Merges includes so that the result is a valid +include+
-        def merge_includes(first, second)
-         (Array.wrap(first) + Array.wrap(second)).uniq
-        end
-
         def build_association_joins(joins)
           join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, joins, nil)
           relation = active_relation.table

activerecord/lib/active_record/calculations.rb

@@ -155,7 +155,8 @@ def construct_calculation_arel(options = {}, merge_with_relation = nil)
           validate_calculation_options(options)
           options = options.except(:distinct)
 
-          includes = merge_includes(merge_with_relation ? merge_with_relation.includes_values : [], options[:include])
+          merge_with_includes = merge_with_relation ? merge_with_relation.includes_values : []
+          includes = (merge_with_includes + Array.wrap(options[:include])).uniq
 
           if includes.any?
             merge_with_joins = merge_with_relation ? merge_with_relation.joins_values : []