#10141: Kind inference regression in closed type families -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: closed Priority: highest | Milestone: 7.10.1 Component: Compiler | Version: 7.10.1-rc2 Resolution: invalid | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by goldfire): * status: new => closed * resolution: => invalid Comment: This is by design. As I discovered en route to the solution to #9200, the old kind inference for closed type families was bogus. For the type family above, what should the return kind be? `k`, `k2`, and `*` are all viable options. Thus, this type family has no principal kind and should be rejected. Another was of looking at this is that `G` does not have a CUSK. Therefore, its right-hand side must use kind variables uniformly -- which it doesn't, because the first two equations must specialize `k` to `*`. So, closing as invalid. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10141#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler