...unless that module is already imported.
However, autocomplete does suggest functions from all installed packages, even though they arent imported (and then automatically adds that import and possibly even cabal dependency, which is great)
This will be fixed as part of the next major feature I'm working on, which is to have a db of all haskell files in workspace. Currently we have scion-browser which gives us a view of the installed packages, but we don't have access to all the files in the workspace yet.
Done, will be part of next release (probably called 2.3). https://github.com/JPMoresmau/eclipsefp/commit/f3eb3387d448dbf36c43a7f3cc6bcc2a8d5f7a79