#15290: QuantifiedConstraints: panic "addTcEvBind NoEvBindsVar" -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: | QuantifiedConstraints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: 9123, 14883 Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Yes, I agree. I'll stop the panic (by refraining from using quantified constraints if I have no place to put the evidence) but that will make GHC reject `deriving` for * A higher rank method * That makes essential use of a quantified constraint * Under a forall I don't see how to avoid that restriction. If anyone else does, please say so! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15290#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler