[CX] correlated aggregation columns

from emp as e 

group by dept group as g

let highest_salary = max(e.salary),

          best_paid = (from g

                                where g.e.salary = highest_salary

                                select g.e.name

                               )

select dept, highest_salary, best_paid;

"msg": "Variable $$26 could not be found in any input schema.",