Lookup module and package defining <<x>?

Has somene already implemented something like: $ghc-pkg --where-from ParseError package parsec: defining modules: Text.ParserCombinators.Parsec.Error, Text.ParserCombinators.Parsec ? lambdabot @index does what I want, but not with my libs installed only locally.. This might be used by any developement system for easily importing modules.. If not I'll start working on this and I'll post again after needing help ;) or finishing It can't be that hard because there is already ghc-pkg list and ghc --show-iface ... Marc