#12630: Assertion failed with BuildFlavour = devel2 -------------------------------------+------------------------------------- Reporter: pacak | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 Type of failure: Compile-time | (amd64) crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by pacak): This code still triggers the issue in ghc-8.0 branch as of 24 Oct 2016, code above - no longer does that. {{{#!hs {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE PolyKinds #-} module A where import GHC.Generics class Enum' f where enum' :: [f a] toEnumDefault :: (Generic a, Enum' (Rep a)) => Int -> a toEnumDefault i = let l = enum' in if (length l > i) then to (l !! i) else error "toEnum: invalid index" class GEnum a }}} {{{ [1 of 1] Compiling A ( Generics/Deriving/Enum.hs, Generics/Deriving/Enum.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1.20161022 for x86_64-unknown-linux): ASSERT failed! CallStack (from HasCallStack): assertPprPanic, called at compiler/types/TyCoRep.hs:2008:56 in ghc:TyCoRep checkValidSubst, called at compiler/types/TyCoRep.hs:2044:17 in ghc:TyCoRep substTy, called at compiler/types/TyCoRep.hs:1986:3 in ghc:TyCoRep in_scope InScope [a2Um :-> a_a2Um[sk], a2Ur :-> k_a2Ur[tau:3], a2Us :-> f_a2Us[tau:3], a2Uu :-> a_a2Uu[sk]] tenv [a2Um :-> a_a2Uu[sk]] tenvFVs [a2Ui :-> k_a2Ui[tau:5], a2Uu :-> a_a2Uu[sk]] cenv [] cenvFVs [] tys [[f_a2Us[tau:3] a_a2Um[sk]]] cos [] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12630#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler