so there is currently a massive memory leak in SourceKitService when using the latest snapshot of Swift (since 22.12.15).
After some git bisecting I narrowed the introduction of the memory leak down to the following commits:
"Clang importer: enable the Swift name lookup tables by default."
"Clang importer: delete most of the old name lookup path. NFC"
lnspecting SourceKitService in Activity Monitor shows lots of duplicate open files.
At this point I'm a bit out of my depth and don't know how to continue further.
I figured that the best next step would be to share my findings on the mailing list and open a new bug.
Hopefully someone more familiar with the code base can find the origin of the leak.
The bug report with more information can be found here: https://bugs.swift.org/browse/SR-562