[Haskell-beginners] import checking and filtering

Maybe I'm losing it, but I seem to remember, when I first started out with Haskell, using some program which would check the import list in each of my source files, and then it would output a new import list that only imported exactly those functions that my program actually used. At the time I didn't think that was important, but now I really want it, yet I can't remember which utility it was that did this. Does anyone happen to know which utility it is I'm thinking of? -- frigidcode.com indicium.us