Panic, "falls into a hole"

{-# language PolyKinds #-}
{-# language FlexibleContexts #-}
{-# language ConstraintKinds #-}
{-# language FlexibleInstances #-}
{-# language FunctionalDependencies #-}

import GHC.Types (Constraint)

class Ríki (p :: i -> i -> *)
class (Ríki p) => Varpi p q f | f -> p q
instance Varpi () () f => Varpi (->) (->) (Either f) where

causes

% ghci -ignore-dot-ghci /tmp/testing.hs 
GHCi, version 8.1.20160117: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( /tmp/testing.hs, interpreted )

/tmp/testing.hs:11:10: error:ghc: panic! (the 'impossible' happened)
  (GHC version 8.1.20160117 for x86_64-unknown-linux):
        fvProv falls into a hole {a13R}

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

> 
Leaving GHCi.

Trac metadata

Trac field	Value
Version	7.10.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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