#12476: Error building HList -------------------------------------+------------------------------------- Reporter: | Owner: DanielWaterworth | Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ [21 of 28] Compiling Data.HList.Labelable ( Data/HList/Labelable.hs, .stack-work/dist/x86_64-linux/Cabal-1.24.0.0/build/Data/HList/Labelable.o ) /home/dan/fun/HList/Data/HList/Labelable.hs:137:9: warning: [-Wredundant- constraints] • Redundant constraints: (LabeledOpticF ty f, LabeledOpticP ty p) • In the type signature for: hLens' :: (ty ~ LabelableTy LabeledR, LabeledOpticF ty f, LabeledOpticP ty p, LabeledOpticTo ty x to) => Label x -> to (p a (f b)) (p (LabeledR s) (f (LabeledR t))) In the instance declaration for ‘Labelable x LabeledR s t a b’ /home/dan/fun/HList/Data/HList/Labelable.hs:211:10: warning: [-Wredundant- constraints] • Redundant constraint: ToSym (a b c) x • In the instance declaration for ‘EnsureLabel (a b c) (Label x)’ /home/dan/fun/HList/Data/HList/Labelable.hs:277:10: warning: [-Wredundant- constraints] • Redundant constraint: HRLabelSet bs • In the instance declaration for ‘Projected Record s t a b’ /home/dan/fun/HList/Data/HList/Labelable.hs:332:10: warning: [-Wredundant- constraints] • Redundant constraint: ToSym (to p q) x • In the instance declaration for ‘HExtend (to p q) (Proxy '[])’ /home/dan/fun/HList/Data/HList/Labelable.hs:337:10: warning: [-Wredundant- constraints] • Redundant constraint: ToSym (to p q) x • In the instance declaration for ‘HExtend (to p q) (Proxy (x : xs))’ /home/dan/fun/HList/Data/HList/Labelable.hs:344:10: warning: [-Wredundant- constraints] • Redundant constraint: ToSym (to p q) x • In the instance declaration for ‘HExtend (to p q) (Proxy (Lbl n ns desc : xs))’ ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): pprIfaceCo Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} This is the version I was building: https://github.com/DanielWaterworth/HList/tree/66643fb75771e71192ab380e4f2ed... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12476 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler