Panic with TypeFamilies with type synonym instances

The code below brings GHC to panic.

{-# LANGUAGE TypeFamilies, FlexibleInstances #-}

module Bug where

type Node v = Int

class Predicate a where
   type Var a
   variable :: Var a -> a

instance Predicate (Node v) where
   type Var (Node v) = v
   variable = undefined

Panic details:

ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.2 for i386-unknown-mingw32):
	tcTyVarDetails
    ( v{tv aa3} [tv] :: ghc-prim:GHC.Prim.*{(w) tc 34d} )

Can be reproduced on GHC versions 7.4.2 and 7.6.1.

Possibly, a duplicate of http://hackage.haskell.org/trac/ghc/ticket/7458, but difficult to tell without additional info on the latter.

Trac metadata

Trac field	Value
Version	7.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	rotsor@gmail.com
Operating system
Architecture