Template Haskell: dataToExpQ and constructor mis-match

[Conal Elliott]

I'm looking for a reliable way to turn values into Template Haskell
expressions. I thought dataToExpQ from Language.Haskell.TH.Quote was the
ticket, but it appears to produce constructors different from those
produced by [| ... |], including [], (:), (), and (,). Here's an example
run for (). I'm using template-haskell-2.5.0.0:

    GHCi, version 7.0.4: http://www.haskell.org/ghc/  :? for help
    Prelude> import Data.Data
    Prelude Data.Data> import Language.Haskell.TH
    Prelude Data.Data Language.Haskell.TH> :set -XTemplateHaskell
    Prelude Data.Data Language.Haskell.TH> import Language.Haskell.TH.Quote
    Prelude Data.Data Language.Haskell.TH Language.Haskell.TH.Quote> u1 <-
runQ (dataToExpQ (const Nothing) ())
    Prelude Data.Data Language.Haskell.TH Language.Haskell.TH.Quote> u2 <-
runQ [| () |]
    Prelude Data.Data Language.Haskell.TH Language.Haskell.TH.Quote> u1
    ConE ()
    Prelude Data.Data Language.Haskell.TH Language.Haskell.TH.Quote> u2
    ConE GHC.Unit.()
    Prelude Data.Data Language.Haskell.TH Language.Haskell.TH.Quote> u1 ==
u2
    False

Any suggestions?

-- Conal
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