ghc-8.0.1: panic! (the 'impossible' happened) filterImports/combine (double import)

It's a distilled example or repa-devil-0.3.2.6 build failure:

-- Cursored.hs:
{-# LANGUAGE TypeFamilies #-}
module Cursored where

class Source r where
    data Array r

instance Source () where
    data Array () = F { f :: Int }

-- Bug.hs:
module DevIL () where

import Cursored (Array(..), Source(..))

[1 of 2] Compiling Cursored         ( Cursored.hs, Cursored.o )
[2 of 2] Compiling DevIL            ( Bug.hs, Bug.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.1 for x86_64-unknown-linux):
        filterImports/combine
  (Array, Array{Array, F, f}, Nothing)
  (Array, Source{Source, Array}, Nothing)

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

The error is the same as #11959 (closed) but involved entities are slightly different.

Trac metadata

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