guarantee a list in the alias tracker so we can remove a conditional

activerecord/lib/active_record/associations/alias_tracker.rb

@@ -8,8 +8,8 @@ class AliasTracker # :nodoc:
       attr_reader :aliases, :connection
 
       # table_joins is an array of arel joins which might conflict with the aliases we assign here
-      def initialize(connection, table_joins = [])
-        @aliases     = Hash.new { |h,k| h[k] = initial_count_for(k, table_joins) }
+      def initialize(connection, table_joins)
+        @aliases = Hash.new { |h,k| h[k] = initial_count_for(k, table_joins) }
         @connection  = connection
       end
 
@@ -46,8 +46,6 @@ def aliased_name_for(table_name, aliased_name)
       private
 
         def initial_count_for(name, table_joins)
-          return 0 if Arel::Table === table_joins
-
           # quoted_name should be downcased as some database adapters (Oracle) return quoted name in uppercase
           quoted_name = connection.quote_table_name(name).downcase
 

activerecord/lib/active_record/associations/association_scope.rb

@@ -12,7 +12,7 @@ def scope(association, connection)
         reflection    = association.reflection
         scope         = klass.unscoped
         owner         = association.owner
-        alias_tracker = AliasTracker.new connection
+        alias_tracker = AliasTracker.new(connection, [])
 
         scope.extending! Array(reflection.options[:extend])
         add_constraints(scope, owner, klass, reflection, alias_tracker)

activerecord/lib/active_record/relation/finder_methods.rb

@@ -347,7 +347,15 @@ def construct_join_dependency(joins = [])
     end
 
     def construct_relation_for_association_calculations
-      apply_join_dependency(self, construct_join_dependency(arel.froms.first))
+      from = arel.froms.first
+      if Arel::Table === from
+        apply_join_dependency(self, construct_join_dependency)
+      else
+        # FIXME: as far as I can tell, `from` will always be an Arel::Table.
+        # There are no tests that test this branch, but presumably it's
+        # possible for `from` to be a list?
+        apply_join_dependency(self, construct_join_dependency(from))
+      end
     end
 
     def apply_join_dependency(relation, join_dependency)