#15852: Bad axiom produced for polykinded data family -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: 8.7 Resolution: | Keywords: TypeFamilies, | TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5328 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"014d6c1f08808c4dab6cba80efdc634527d91086/ghc" 014d6c1/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="014d6c1f08808c4dab6cba80efdc634527d91086" Fix #15852 by eta expanding data family instance RHSes, too When I defined `etaExpandFamInstLHS`, I blatantly forgot to eta expand the RHSes of data family instances. (Actually, I claimed that they didn't //need// to be eta expanded. I'm not sure what I was thinking.) This fixes the issue by changing `etaExpandFamInstLHS` to `etaExpandFamInst` and, well, making it actually eta expand the RHS. Test Plan: make test TEST=T15852 Reviewers: goldfire, bgamari Reviewed By: goldfire Subscribers: rwbarton, carter GHC Trac Issues: #15852 Differential Revision: https://phabricator.haskell.org/D5328 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15852#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler