AssertionError: Not-null boxed primitive should come back as primitive when translating correlated variables

Queries introducing correlated variables on boxed primitive fields throw an assertion error when they are translated to generated code in the Enumerable convention.

For example, consider the following query where e.commission is a field of type Integer:

SELECT empid FROM emps e 
WHERE NOT EXISTS 
     (SELECT 1 FROM depts d WHERE d.deptno=e.commission)