Tool to preprocess template haskell definitions?

Hello

I remember someone having written a small utility
to preprocess a Haskell source file with TH definitions
and generate a new file with the TH bits replaced
by their resulting slices.

If anyone knows the utility or a way to do this
pointers would be nice. I am trying to use
Haddock to create documentation, but datatypes
are created with TH...

- Einar Karttunen