This too was wrong and the real problem was me putting "monads-tf" in my build dependencies instead of "mtl". I got bit by using a macro on that list of "try ad

This too was wrong and the real problem was me putting "monads-tf" in my build dependencies instead of "mtl". I got bit by using a macro on that list of "try adding X dependency". In any case, the original post is now updated and everything working.