1 files changed, 21 insertions, 4 deletions
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 9cabd1af13..c562f214c9 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -37,7 +37,16 @@ module ActiveRecord
     # Note: not all valid {Relation#select}[rdoc-ref:QueryMethods#select] expressions are valid #count expressions. The specifics differ
     # between databases. In invalid cases, an error from the database is thrown.
     def count(column_name = nil)
-      return super() if block_given?
+      if block_given?
+        unless column_name.nil?
+          ActiveSupport::Deprecation.warn \
+            "When `count' is called with a block, it ignores other arguments. " \
+            "This behavior is now deprecated and will result in an ArgumentError in Rails 5.3."
+        end
+
+        return super()
+      end
+
       calculate(:count, column_name)
     end
 
@@ -73,7 +82,16 @@ module ActiveRecord
     #
     #   Person.sum(:age) # => 4562
     def sum(column_name = nil)
-      return super() if block_given?
+      if block_given?
+        unless column_name.nil?
+          ActiveSupport::Deprecation.warn \
+            "When `sum' is called with a block, it ignores other arguments. " \
+            "This behavior is now deprecated and will result in an ArgumentError in Rails 5.3."
+        end
+
+        return super()
+      end
+
       calculate(:sum, column_name)
     end
 
@@ -368,9 +386,8 @@ module ActiveRecord
         relation.select_values = [aliased_column]
         subquery = relation.arel.as(subquery_alias)
 
-        sm = Arel::SelectManager.new relation.engine
         select_value = operation_over_aggregate_column(column_alias, "count", distinct)
-        sm.project(select_value).from(subquery)
+        Arel::SelectManager.new(subquery).project(select_value)
       end
   end
 end