Re: [GHC] #13272: DeriveAnyClass regression involving a rigid type variable

#13272: DeriveAnyClass regression involving a rigid type variable -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler (Type | Version: 8.1 checker) | Resolution: | Keywords: Generics Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones ): In [changeset:"fd841f877ab7a991f667a50b401404927f6f599c/ghc" fd841f87/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="fd841f877ab7a991f667a50b401404927f6f599c" Fix DeriveAnyClass (again) This patch fixes Trac #13272. The general approach was fine, but we were simply not generating the correct implication constraint (in particular generating fresh unification variables). I added a lot more commentary to Note [Gathering and simplifying constraints for DeriveAnyClass] I'm still not very happy with the overall architecture. It feels more complicate than it should. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13272#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler