Unexpected behavior with & and multiple __in queries on the same field

[K900]

Hi! I'm building a long query by &-ing multiple smaller ones. It looks like when multiple __in queries on one field are combined with &, the resulting query combines all __in parameters into a single list, which produces incorrect results.

For example, running SomeModel.objects.filter(Q(some_id__in=[1]) & Q(some_id__in=[2])) should return nothing (and works correctly in upstream Django with an SQL database), but returns two objects with some_id's 1 and 2 in Django-Nonrel with MongoDB on the backend.

The SQL query is correct here: SELECT some_id, some_other_columns FROM some_table WHERE (some_table.some_id IN (1) AND some_table.some_id IN (2)).

The Mongo query, however, is (as logged by Mongo itself): "query" : {"find" : "some_collection", "filter" : {"some_id" : {"$in" : [1, 2]}}, "ntoreturn" : 21}.

Using Python 2.7.12, MongoDB 3.2.7, pip freeze:
Django==1.6.11
django-mongodb-engine==0.6.0
djangotoolbox==1.8.0
pymongo==2.8