Re: [GHC] #9574: GHC Panic: No Skolem Info

#9574: GHC Panic: No Skolem Info -------------------------------------+------------------------------------- Reporter: ian_mi | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones ): In [changeset:"171101beca39befde191baff5027c417bcc709ee/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="171101beca39befde191baff5027c417bcc709ee" Kind variables in RHS of an associated type instances should be bound on LHS This patche fixes Trac #9574. The previous Note [Renaming associated types] in RnTypes appears to me to be wrong; it confused class and instance declarations. I have: * Treated kind and type variables uniformly. Both must be bound on the LHS of an associated type instance. Eg instance C ('KProxy :: KProxy o) where type F 'KProxy = NatTr (Proxy :: o -> *) is illegal because 'o' is not bound on the LHS of the instance. * Moved the Note to RnSource and fixed it up This improves the error message from T7938. However it made the code in T6118 incorrect. We had: instance SingE (a :: Maybe k) where type Demote a = Maybe (Demote (Any :: k)) and that is now rejected, rightly I think. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9574#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler