[Template-haskell] mysterious type inference problem in splice

[Daniel Brown]

I'm using Template Haskell for the first time, trying to do some code
manipulation, and I'm getting some error messages I don't understand.
In the code below, idwrap[01] behave as expected, but idwrap2 does not
work the same way:

    *Q> $(idwrap0 i1)
    1
    *Q> $(idwrap1 i1)
    1
    *Q> $(idwrap2 i1)

    <interactive>:1:
        No instance for (Num ExpQ)
          arising from the literal `1' at <interactive>:1
        In the first argument of `idexp', namely `1'
        In the definition of `it': it = $[splice](idwrap2 i1)

What's going on here?  Why does the system want to prove (Num ExpQ)?  (I
should add that I'm also new to GHC, though I have used Hugs a fair
amount.)

-- Dan.

------------------------------------------------------------------------

module Q where

import Language.Haskell.THSyntax

idq   = id
idexp = id :: ExpQ -> ExpQ

idwrap0 e = appE (varE "GHC.Base:id") e
idwrap1 e = appE (varE "Q:idq") e
idwrap2 e = appE (varE "Q:idexp") e

i1 = litE (integerL 1)