Error building HList

[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/66643fb75771e71192ab380e4f2ed56e37650f07

This may be a duplicate of #12242 (closed)