#16191: GHC Panic deriving unbox vector (StrictData/unbox-strict-fields interaction) -------------------------------------+------------------------------------- Reporter: dbeacham | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: 8.6.3 Resolution: duplicate | Keywords: Operating System: Linux | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: #16141 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Marge Bot <ben+marge-bot@…>): In [changeset:"a5373c1fe172dee31e07bcb7c7f6caff1035e6ba/ghc" a5373c1/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="a5373c1fe172dee31e07bcb7c7f6caff1035e6ba" Fix bogus worker for newtypes The "worker" for a newtype is actually a function with a small (compulsory) unfolding, namely a cast. But the construction of this function was plain wrong for newtype /instances/; it cast the arguemnt to the family type rather than the representation type. This never actually bit us because, in the case of a family instance, we immediately cast the result to the family type. So we get \x. (x |> co1) |> co2 where the compositio of co1 and co2 is ill-kinded. However the optimiser (even the simple optimiser) just collapsed those casts, ignoring the mis-match in the middle, so we never saw the problem. Trac #16191 is indeed a dup of #16141; but the resaon these tickets produce Lint errors is not the unnecessary forcing; it's because of the ill-typed casts. This patch fixes the ill-typed casts, properly. I can't see a way to trigger an actual failure prior to this patch, but it's still wrong wrong wrong to have ill-typed casts, so better to get rid of them. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16191#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler