Dear Cabal developers If you look at http://hackage.haskell.org/trac/ghc/ticket/3951 you'll see an example of a very confusing link-time error message. The ultimate cause was that a package author omitted one of the modules when listing the package manifest (in exposed and hidden modules). But there is no error when building the package -- the error only shows up when linking a complete application that uses the package. This is obviously bad. When Cabal builds the package, we should clearly check that no modules are omitted. You probably have a ticket on this already, but I thought I'd mention it. Simon