ScriptRunner: How to custom extend aggregate JQL function

[Hubbitus]

I've try implement custom JQL function, just copy/paste `ScriptRunner-5.3.9.jar:/com/onresolve/jira/groovy/jql/AggregateExpression.groovy` into `$JIRA_HOME/scripts/com/onresolve/jira/groovy/jql/AggregateExpressionWithGroupBy.groovy` and change class name to `AggregateExpressionWithGroupBy` and change name:

@Override
String getFunctionName() {
    "aggregateExpressionWithGroupBy"
}

 After hot `scan` link new function appeared in functions list:

By search results it looks like working, but I got error "Negative array index [-1] too large for array size 0" instead of totals:

If I try just extend some JQL function I got cast error, because of different classloaders I think:

class AggregateExpressionWithGroupBy extends AggregateExpression {

error:

Cannot cast object 'com.onresolve.jira.groovy.jql.AggregateExpression@2d03fc56' with class 'com.onresolve.jira.groovy.jql.AggregateExpression' to class 'com.onresolve.jira.groovy.jql.AggregateExpression'

[Hubbitus]

deleted