#11732: Deriving Generic1 interacts poorly with TypeInType -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: TypeInType, | Generics Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): I claim that {{{ data Proxy k (a :: k) = ProxyCon deriving Generic1 }}} should fail outright. I don't think GHC should be in the business of inferring values for visible parameters like `k`, even when it could. Instead, it should be this: {{{ deriving instance Generic1 (Proxy *) }}} Note that this applies to `Functor` as much as it does to `Generic1`. As for the `partitionInvisibles` piece: yes, that is all suspicious. I conjecture that we should never call `partitionInvisibles` on a data ''instance'' tycon, but only on the data ''family'' tycon. Perhaps we need to teach `partitionInvisibles` how to work on data instances. But not today, I'm afraid. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11732#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler