Don't require calculations to be aliased to a column

Arel has changed so that `.sum` no longer aliases `SUM(the_column)` to
`sum_id`. This means the type returned by the adapter will be at the key
`"SUM(the_column)"`. Longer term, we should eventually be able to retain
type information from the AR::Base subclasses used in joined queries

activerecord/lib/active_record/relation/calculations.rb

@@ -253,7 +253,7 @@ module ActiveRecord
 
         select_value = operation_over_aggregate_column(column, operation, distinct)
 
-        column_alias = select_value.alias
+        column_alias = select_value.alias || select_value.to_sql
         relation.select_values = [select_value]
 
         query_builder = relation.arel

activerecord/test/cases/calculations_test.rb

@@ -461,7 +461,6 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal 7, Company.includes(:contracts).sum(:developer_id)
   end
 
-
   def test_from_option_with_specified_index
     if Edge.connection.adapter_name == 'MySQL' or Edge.connection.adapter_name == 'Mysql2'
       assert_equal Edge.count(:all), Edge.from('edges USE INDEX(unique_edge_index)').count(:all)