Help on first ticket

Hello! I apologize if this isn't the right place to ask; if it isn't please steer me in the right direction. Would anyone be willing to advise me on my first ticket? I've been trying to work on it on and off but haven't made much progress on my own. It's ticket #9370: https://ghc.haskell.org/trac/ghc/ticket/9370 I think I understand the issue conceptually but I don't know where to look for the code that needs to be changed.. Thanks!