Avoid lambda scopes when possible

Lambda scopes require a bunch more work.  Ideally the `scope` list would
be a homogeneous collection.  In this case, the reflection knows how to
construct the right reflection for this join, so lets just construct
that relation rather than instance execing to figure it out later.

1 files changed, 1 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index d923050822..81ec4924b0 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -807,9 +807,7 @@ module ActiveRecord
       end
 
       def source_type_scope
-        type = foreign_type
-        source_type = options[:source_type]
-        lambda { |object| where(type => source_type) }
+        through_reflection.klass.where(foreign_type => options[:source_type])
       end
 
       def has_scope?