Multiple occurrences of query vars in pattern and aggregates

With this query:
```
(q '[:find (count ?e) .
     :with ?i
     :where [?e :r ?e ?i]]
   [[1 :r 1 10]
    [2 :r 1 11]])
```
I get `1` with Datomic but `2` in datascript. It appears the test for two occurrences of a query variable is tested too late.