GHC panic related to hybrid-vectors

The following module makes GHC 8.0.1 panic when the fromList declaration is uncommented:

import qualified Data.Vector.Hybrid as VH
import qualified Data.Vector.Unboxed as VU
import qualified Data.Vector as V

data SHVector a = SHV {-# UNPACK #-} !Int !(VH.Vector VU.Vector V.Vector (Int, a)) deriving (Eq)

fromList :: Int -> [(Int, a)] -> SHVector a
fromList n ll = SHV n (VH.fromList ll)

Crash message follows:

ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.1 for x86_64-apple-darwin):
	Template variable unbound in rewrite rule
  Variable: sc_shyr
  Rule "SC:$j0"
  Rule bndrs: [sc_shyr, sc_shys, sc_shyt, sg_shyu, sc_shyq]
  LHS args: [sc_shyq,
             (MV
                @ (Mutable Vector)
                @ (Mutable Vector)
                @ (PrimState (ST RealWorld))
                @ (Int, a_aeG1)
                @ Int
                @ a_aeG1
                @~ (<(Int, a_aeG1)>_N
                    :: ((Int, a_aeG1) :: *) ~# ((Int, a_aeG1) :: *))
                sc_shys
                sc_shyt)
             `cast` (sg_shyu
                     :: (MVector
                           (Mutable Vector)
                           (Mutable Vector)
                           (PrimState (ST RealWorld))
                           (Int, a_aeG1) :: *)
                        ~R#
                        (Mutable
                           (Vector Vector Vector)
                           (PrimState (ST RealWorld))
                           (Int, a_aeG1) :: *))]
  Actual args: [sc_shyk,
                wild_ahdD
                `cast` (Sub
                          (Sym (D:R:MutableVector[0] <Vector>_N <Vector>_N)) <PrimState
                                                                                (ST
                                                                                   RealWorld)>_N <(Int,
                                                                                                   a_aeG1)>_N
                        :: (MVector
                              (Mutable Vector)
                              (Mutable Vector)
                              (PrimState (ST RealWorld))
                              (Int, a_aeG1) :: *)
                           ~R#
                           (Mutable
                              (Vector Vector Vector)
                              (PrimState (ST RealWorld))
                              (Int, a_aeG1) :: *))]

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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