`deriving instance Generic (HsExpr Id)` raises panic

Input file:

{-# LANGUAGE FlexibleInstances, DeriveGeneric, StandaloneDeriving #-}
module GHCGeneric where

import GHC
import GHC.Generics

deriving instance Generic (HsExpr Id)

Result:

GHCi, version 7.4.2: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling GHCGeneric       ( /home/daniel/dev/dataflow/GHCGeneric.hs, interpreted )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.2 for i386-unknown-linux):
        tcTyVarDetails ( id{tv a3cX} [tv] :: *{(w) tc 34d} )

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

Regards,[[BR]] Daniel

Trac metadata

Trac field	Value
Version	7.4.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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