#12860: GeneralizedNewtypeDeriving + MultiParamTypeClasses sends typechecker into an infinite loop -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Keywords: FunDeps, Resolution: | deriving Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
So perhaps we need to carve out the bit that checks the coverage condition and just check that.
Or just call `checkValidInstance` with a Note explaining why you might think it's not necessary (the exotic-derived Note), and the example from this ticket explaining why it actually is. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12860#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler