I would like to find all epics that have "Issues in Epic" from a specific Project. Current JQL:
project = FOO AND issuetype = Epic AND key in (FOO-1, FOO-2, FOO-3)
I can add and issueFunction in linkedIssuesOf("project = BAR and issueFunction in hasLinkType('Epic-Story Link')"), but it gives me epics which have other types of linked issues (eg. clones, related ..)
I was able to reproduce the described behavior.
These are all link types: Blocks, Cloners, Duplicate, Epic-Story Link, Gantt End to End, Gantt End to Start, Gantt Start to End, Gantt Start to Start, Parent-Child Link, Problem/Incident, Relates, Solves
It seems that Epic-Story Link is handled like a super type of some of the other ones during query evulation. That's just a suggestion and I dunno why this should be.
However, the following query should work for your purpose
project = FOO AND issuetype = Epic AND issueFunction in linkedIssuesOf("project = BAR AND 'Epic Link' is not EMPTY")
Why not just create a scrum board, import all issues you want to sort on and see which ones are empty opening the epics panel?